Study of the Sympathetic Vasoconstrictor Nerves to the Vessels of the Dog Hind Limb

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1 Study f the Sympathetic Vascnstrictr Nerves t the Vessels f the Dg Hind Limb By David E. Dnald, Ph.D., and David A. Fergusn ABSTRACT In anesthetized dgs, the vascnstrictr nerves t the vessels f the hind limb left the spinal crd in the anterir spinal nerve rts frm T-10 thrugh L- levels. Maximal vascnstrictr respnses ccurred n stimulatin f the T- 12, T-13, and L-l rts; nne ccurred n stimulatin f rts caudal t L-. The nerves first entered the lumbar paravertebral chain at r abve L-l; the last pint f entry was at the L-, L- level. N fibers left the lumbar chain at L-l, L-2, and L-3 levels. The first pint f exit was at L-, and nerves cntinued t leave as far distal as S-l, the mst caudal pint examined. The maximal respnse t stimulatin f the lumbar chain was at the L-, L- level. With a single exceptin, the respnses t electric stimulatin f the anterir spinal nerve rts, lumbar chain, r sympathetic ganglia were cnfined t the vessels f the ipsilateral limb. In 22 dgs with unilateral sympathectmy (L-2 thrugh L-7), changes in hind-limb vascular resistance were induced reflexly r by electric stimulatin f the anterir spinal rts. The results indicated that sympathetic cntrl f the resistance vessels f the hind limb was still absent 77 days after sympathectmy. ADDITIONAL KEY WORDS canine limb perfusin limb bld flw sympathetic utflw reflex vascnstrictin vasmtr nerves anterir spinal nerve rts lumbar paravertebral chain peripheral resistance sympathectmy I. FUNCTIONAL ANALYSIS OF THE ROUTES TAKEN BY SYMPATHETIC VASOCON- STRICTOR NERVES FROM THE SPINAL CORD TO THE HIND LIMB VESSELS OF THE DOG T investigate sympathetic nervus cntrl f vascular resistance in actively cntracting skeletal muscle in the dg, it is necessary t interrupt the sympathetic nerves t the vessels f the hind limb in a manner that permits study f the cnscius exercising animal shrtly after the vascular denervatin. Essential t such a technique is a knwledge f the pathways taken by the sympathetic vasmtr fibers frm the spinal crd t the hind limbs, particularly where they enter and leave the lumbar sympathetic chain. This infrmatin is als necessary t assess the degree t which the sympathectmy has interrupted neur- Frm the May Clinic and May Fundatin, Sectin f Surgical Research, Rchester, Minnesta 910. This investigatin was supprted in part by U. S. Public Health Service Research Grant HE-613 frm the Natinal Heart Institute. Received May 20, Accepted fr publicatin December 1, genie cntrl f the peripheral vasculature. The precise infrmatin needed was nt available in previus studies (1-). Methds I Studies were cnducted in 22 dgs in which anesthesia was induced by sdium thipental, 20 nig/kg, and a-chlralse, 60 mg/kg, and maintained by a-chlralse, 10 mg/kg/hur. Atrpine was given in an initial dse, f 0.2 mg/kg and repeated at intervals f 1 hur. Heparin was given in an initial dse f 3 mg/kg and at hurly intervals in a dse f 1. mg/kg. Gallamine triethidide (Flaxedil) was given in a dse f 0 mg at intervals f 1 hur t prevent muscle mvement. These drugs were given intravenusly. The animals were artificially ventilated with xygen at a rate f 1 cpm and a peak inspiratry pressure f 12 cm H 2 O. Exit f Vascnstrictr Fiber frm the Spinal Crd. The spinal crd was expsed frm the T-9 thrugh the L-7 level. At each segmental level, the anterir spinal nerve rts were islated and the intervening spinal crd was remved. The femral arteries were expsed bilaterally and 171

2 172 DONALD, FERGUSON ligated 2 cm distal t the inguinal ligament. A May-Gibbn, 360, single rller pump was used t perfuse each hind limb separately at cnstant flw with the dg's wn bld thrugh cannulas placed in the femral arteries, cranial and caudal t the ligature. The cranial femral and superficial circumflex iliac arteries were divided between ligatures. A heat exchanger in the perfusin system maintained the temperature f the bld at 38 C. The utput f each pump was adjusted initially t btain a perfusin pressure f 120 mm Hg, and after that the perfusin flw was nt altered. Perfusin pressure was measured by a fine catheter intrduced int the bld-flw line and advanced until its tip was just distal t the cannula thrugh which bld was pumped int the hind limb. Central artic pressure was measured by a catheter inserted int a brachial artery and advanced int the ascending arta. Each catheter was attached t a strain gauge (Statham Mdel P23) whse utput was led int an ultravilet-light recrder t allw simultaneus bservatin f all three pressures. At each segmental level f the crd, first ne and then the ther anterir spinal nerve rt was stimulated electrically with mnphasic rectangular pulses f 10 v, 1 cps, and 3-msec duratin. An increase in limb perfusin pressure ccurring within 3 secnds f the nset f stimulatin was accepted as a valid vasmtr respnse. A cnstant infusin f fresh heparinized dnr bld was used t sustain mean systemic bld pressure abve 100 mm Hg thrughut the experiment. Entrance f Vascnstrictr Fibers int the Lumbar Paravertebral Chain. Midline lapartmy was perfrmed, and the lumbar sympathetic chain was expsed bilaterally. Divisin f the phrenic-abdminal artery and vein, and mbilizatin f the pars lumbalis f the diaphragm allwed the expsure t be carried t the level f L-l. A cannula was inserted int the terminal prtin f the arta, just distal t the rigin f the external iliac arteries, and the bld was directed int tw separate pump-perfusin systems. Each hind limb was perfused separately thrugh a cannula inserted int the distal prtin f the external iliac artery. The deep circumflex iliac, internal iliac, median sacral, and deep femral arteries were divided between ligatures t reduce cllateral inflw int the perfused hind limb. Perfusin and central artic pressures were measured as previusly described in this sectin, the utput frm each pump having been adjusted initially t btain a perfusin pressure f 120 mm Hg. In tw dgs f this grup, bth hind limbs were perfused frm a cmmn cnstant head f pressure, and the flw t each limb was measured by cannulating square-wave electrmagnetic flw transducers (300 Series 1 ). The activity f the sympathetic vascnstrictr nerves t the vessels f the hind limbs was altered reflexly by varying the pressure in bth cartid sinuses which had been vascularly islated by the Missejeff technique (6). Ligatin f the ccipital artery at its rigin frm the cmmn cartid artery ensured that nly the barreceptrs f the cartid sinus were stimulated. Observatins were made at steady intrasinus pressures f 30 and 200 mm Hg. Bth vagi were sectined in the neck. After a series f cntrl bservatins, the right r the left lumbar sympathetic chain was divided at the level f L-l, just anterir t the mst cephalad ganglin that culd be expsed. The pressure changes in the cartid sinus were then repeated. The cmmunicating rami f the mst cephalad ganglin (usually ppsite L-2) were severed next, and the pressure changes in the cartid sinus were repeated. This prcedure sectin f the cmmunicating rami and expsure f the cartid sinus t static pressures f 30 and 200 mm Hg was repeated with each succeeding ganglin until reflex vascular respnses were n lnger bserved. Bth the right and the left lumbar sympathetic chains were treated as previusly described. During the prcedure, a silk stitch was placed in the lumbar muscles adjacent t each ganglin t allw later identificatin f the ganglin with reference t the lumbar vertebrae. Finally, the ability f each decentralized chain t transmit impulses was tested by electrically stimulating the chain (10 v, 1 cps, 3 msec) at its mst cephalad expsed pint. One animal was prepared as previusly described in this sectin, and the anterir spinal nerve rts were islated frm the level f L-3 t the sacrum. In additin, the abdmen was pened thrugh an incisin in the left flank, and the left lumbar paravertebral sympathetic chain was expsed frm the L-2, L-3 level thrugh the L-6 level. The anterir spinal nerve rts n either side were stimulated electrically at each segmental level (L-3 thrugh L-7) befre and after selected cmmunicating rami cnnected t the left lumbar chain ganglia were cut. Exit f Vascnstrictr Fibers frm the Lumbar Sympathetic Chain. Each hind limb was perfused separately at cnstant flw, and perfusin and artic pressures were measured as described previusly in this sectin. The animals were eviscerated t allw easy access t each lumbar paravertebral chain. A spinal needle was inserted between C-l and the base f the skull t permit the intrductin f a fine plythene catheter int icarlina Medical Electrnics, King, N. C.

3 SYMPATHETIC VASOCONSTRICTOR OUTFLOWS IN DOG 173 the subdural space. Fur milliliters f 10% prcaine hydrchlride were infused thrugh this catheter t prduce a high spinal blck. This prcedure served t prevent reflex vasmtr effects and t btain maximal dilatatin f the vessels f the perfused hind limbs. The right r the left lumbar sympathetic chain was stimulated electrically fr perids f 30 secnds with mnphasic rectangular pulses f 10 v, 1 cps, and 3-msec duratin. An increase in perfusin pressure within 3 secnds f the nset f stimulatin was accepted as a valid vasmtr respnse. The lumbar chain was stimulated first n the cranial side f the mst cephalad ganglin that culd be expsed. This pint was usually beneath the diaphragm at the level f L-2. The lumbar chain was then crushed immediately distal t the ganglin, and the stimulatin was repeated. Finally, the electrdes were applied t the cmmunicating rami and the stimulatin was repeated nce mre. Next, the ganglin immediately caudal t the first was expsed, and the electrdes were applied t the lumbar chain between the first and secnd ganglia. The sequence f stimuli previusly described was carried ut. This entire prcedure was repeated at each succeeding caudal ganglin up t and including the first sacral ganglin. During the prcedure, markers were placed at each pint f stimulatin, and n cmpletin f the experiment, the pints were identified with reference t the immediately adjacent vertebra. The cntralateral sympathetic chain was studied in a similar fashin. Uj IX) X UJ t U. O O CL 10 UJ 0c Results Exit frm Spinal Crd. In the seven animals studied, significant vascnstrictr respnses were btained frm the T-10 thrugh the L- segmental level, with the majr increases in perfusin pressure being bserved n stimulatin f T-12, T-13, and L-l anterir spinal nerve rts f either side. Cnstrictr respnses were nt btained belw the L- segmental level even when stimulatin was cntinued as far distal as the L-7 anterir spinal nerve rts. Individual respnses are shwn in Figure 1. The mean maximal increase in perfusin pressure was bserved at the T-13 level fr bth the right and left sides and was 116 (SD 38) and 122 (SD 1) mm Hg, respectively. In ne animal, stimulatin f the left anterir rt at L-3 resulted in an increase in perfusin pressure f 8 mm Hg in the left leg and f 19 mm Hg in the right leg. The rise in pressure began simultaneusly n bth sides. When stimulatin was stpped, perfusin pressure decreased immediately n the left side, whereas n the right it was unchanged fr 1 secnds and then decreased slwly. This pressure respnse in the right leg was nt present after sectin f the right sciatic nerve. Apart frm Anterir Spinal Nerve Rts Anterir Spinal Nerve Rts 100 r * A 10 // Thracic x 1 2 I 3 Lumbar S A FIGURE r E 1 / / 12 I 13 Thracic f Lumbar Change in perfusin pressure (seven dgs) in respnse t electric stimulatin f islated anterir nerve rts at each vertebral level frm T-10 thrugh L-. Dg hind limb perfused at cnstant flw via femral artery. Each animal indicated by separate symbl.

4 17 DONALD, FERGUSON TABLE 1 Vasdilatatin in Perfused Hind Limb during Stimulatin f Anterir Spinal Nerve Rts f the Dg Side Lumbar anterir spinal nerve rts* Dg stimulated L- L-6 L f J "Values fr dgs 1- shw decrease in perfusin pressure (mm Hg) frm cntrl. Values fr dgs 6 and 7 shw increase in flw (ml/min) frm cntrl at cnstant artic pressure; values shwn are the maximal nes fr each dg. f nerve rts and left hind limb. { nerve rts and right hind limb. the single instance, stimulatin f an anterir spinal nerve rt n ne side did nt effect a vascnstrictr respnse in the cntralateral perfused hind limb. ( mmhg) ISO 0 LEFT LEG Stimulus In six f the seven animals, stimulatin at the L-, L-6, and L-7 levels resulted in a definite vasdilatatin, which was ften mre prnunced n ne side than the ther (Table 1). This vasdilatr respnse had the fllwing features. 1. The pressure r flw did nt return t the cntrl level fr several minutes after stimulatin was stpped. 2. If a secnd stimulus was given 2 t 3 minutes after the first, the magnitude f the respnse was reduced. Ten t 1 minutes was required fr full recvery. 3. The respnse was nt inhibited by intravenus dsage with atrpine sulphate, 0.2 mg/kg, with l-(isprpylamin)-3-(l-naphthylxy) -2-prpanl hydrchlride (prpranll), 1 mg/kg, r with diphenhydramine hydrchlride (Benadryl), 2. mg/kg.. The respnse was present after remval f the paravertebral lumbar sympathetic chain frm L-2 thrugh L-7.. The respnse was nt assciated with visible mvement f the hind limb muscles and culd be btained immediately after treatment with gallamine (0 t 100 mg iv). Figure 2 shws reprductins f tracings btained by stimulating the anterir spinal nerve rts at L-6 in dgs 1 and 7. These (ml/min) 1 Stimulus FIGURE 2 : Separate perfusin f right and left hind limbs at cnstant flw (ne dg). Measurement f mean artic and limb perfusin pressure. Decrease in left-leg perfusin pressure in respnse t stimulatin f islated left anterir spinal nerve rt at level f L-6. : Measurement f bld flw in right (R) and left (L) hind limbs perfused at cnstant artic (A) pressure (ne dg). Increase in bld flw in right leg in respnse t stimulatin f right anterir nerve rt.

5 SYMPATHETIC VASOCONSTRICTOR OUTFLOWS IN DOG 17 Uj a V- Leg LI \ L2 \ L3 L L * FIGURE 3 Leg Reductin in reflex vascnstrictr respnse (seven dgs) in limb perfused at cnstant flw, with prgressive distal sectin f cmmunicating rami between spinal nerves and sympathetic paravertebral lumbar chain. respnses were amng the mst prnunced in this grup f dgs. Entrance int the Lumbar Paravertebral Chain. The individual data frm seven dgs (Fig. 3) shw that the magnitude f the reflex changes in limb perfusin pressure decreased prgressively as the level at which the cnnecting rami were sectined was mved tward the sacrum; there were n changes after sectin f the rami at the L-, L- level. In each animal, the average f the respnses btained befre sectin f the lumbar chain r cnnecting rami was taken as the cntrl, and the subsequent respnses were expressed as percent f this value. At least ten changes f pressure within the cartid sinus were used t btain the cntrl value, and each subsequent pint represented the mean f the respnses t fur changes in sinus pressure. A temprary reductin in the respnse f central artic pressure was assciated with the manipulatins required t expse the pint f sectin f the lumbar chain at L-l, but apart frm this instance, the respnse f central artic pressure t cartid sinus stimulatin was relatively cnstant thrughut each experiment. The mean changes in central artic, right-leg, and left-leg perfusin pressures during the cntrl perid were, respectively, 9 (SD ), 72 (SD 13), and 76 (SD 13) mm Hg. In each animal, direct electric stimulatin f the decentralized lumbar chains at the L-2 level resulted in an increase in limb perfusin pressure. In the dg whse anterir spinal nerve rts were islated, perfusin pressure increased 62 and 36 mm Hg n stimulatin f the left anterir rts at L-3 and L-, respectively. Stimulatin f the right anterir rts gave increases in perfusin pressure f and 30 mm Hg, respectively, at the L-3 and L- levels. N vascnstrictr respnses were btained frm stimulatin f the L-, L-6, and L-7 anterir rts n either side. The vascnstrictr respnse btained at L-3 and L- was cnfined t the ipsilateral limb, with n change in pressure in the cntralateral limb. After sectin f the cmmunicating rami t the left lumbar chain ganglin at the level f L-, there was n respnse t stimulatin f the left L-3 anterir nerve rt, but an increase in perfusin pressure f 0 mm Hg resulted frm stimulatin f the left anterir rt at L-. The cmmunicating rami t the next caudal left lumbar chain ganglin (L-, L- level) were then sectined. Stimulatin f the left anterir rt at L- nw gave n respnse. The electrdes then were applied t the left lumbar chain at the L-2, L-3 level. Stimulatin resulted in an increase in left-leg perfusin pressure f 9 mm Hg. Exit frm Lumbar Paravertebral Chain. The changes in limb perfusin pressures in respnse t electric stimulatin f the right and left lumbar sympathetic paravertebral chains at each segmental level are shwn in Figure. In ne dg (pen square in Fig. ), nly the left chain was stimulated. Maximal respnses were btained at the L- and L-

6 176 DONALD, FERGUSON 100 LEFT SIDE u. 0 c* A ' Uj Cfc Uj X D A LI L 2 \ L3 \ L \ L \ L 6 \ L7 \ 0. t UJ 0 X O I- 100 CK * * * RIGHT SIDE FIGURE Change in perfusin pressure (seven dgs) in limb perfused at cnstant flw in respnse t electric stimulatin f sympathetic lumbar chain at successive vertebral levels frm L-l t sacral level. Lumbar chain was sectined prximal t each electrde psitin befre stimulatin. levels, after which the magnitude f the pressure change declined rapidly. Hwever, pressr respnses were still elicited at the sacral level. At the L- and L- levels, the mean increase in perfusin pressure in this grup f seven dgs was 99 (SD ) and 102 (SD 2) mm Hg in the right and the left leg, respectively. A similar rise and fall was seen in the pattern f increase in limb perfusin pressure in respnse t stimulatin f the cmmunicating rami and f the lumbar chain after the chain had been crushed distal t the segmental ganglin. N increases in perfusin pressure were btained at the L-2 and L-3 levels in any f the seven dgs. A small respnse was btained at the L- level in fur f the seven dgs, bth frm the lumbar chain and the cmmunicating rami. The mean increase in perfusin pressure fr bth hind limbs at each segmental level was 2 (SD ), 11 (SD ), 2 (SD 9), 17 (SD 12), and 1 (SD 1) mm Hg at L-, L-, L-6, L-7, and S-l, respectively. In calculating these averages, the greater f the respnses t the tw mdes f stimulatin was used. In this grup f seven dgs, the vascnstrictr respnse was cnfined t the vessels f the hind limb f the side stimulated, irrespective f whether the stimulus was applied t the lumbar chain, ganglia, r cmmunicating rami. Discussin As in mst studies invlving the sympathetic nervus system, there was cnsiderable variatin frm animal t animal (7), and while part f this variability in respnse undubtedly had an anatmic basis (1), sme at least resulted frm injury t the nerves either during dissectin r subsequent handling. Hwever, we believe the data describe the

7 SYMPATHETIC VASOCONSTRICTOR OUTFLOWS IN DOG 177 Side Side RESPONSE AS PERCENT OF MAXIMUM OR CONTROL FIGURE Vascnstrictr respnses in dg hind limb frm stimulatin f sympathetic nerve fiber at each segmental level frm T-9 thrugh S-l. Averaged data frm studies described under Methds I: Slid circles represent the exit f vascnstrictr fiber frm the spinal crd; x's shw entrance f vascnstrictr fibers int the paravertebral chain; and pen circles and pen triangles shw exit f vascnstrictr fibers frm the lumbar sympathetic chain (pen circle represents stimulatin f lumbar chain intact distal t pint f stimulatin, pen triangle represents stimulatin f islated cmmunicating rami). Seven dgs were used in each f the three studies. Figure gives average rute f sympathetic vascnstrictr fibers frm spinal crd t hind-limb resistance vessels. general curse f the sympathetic vascnstrictr utflw t the hind limb f the dg. This is summarized in Figure, in which the data frm each sectin f the study were averaged. The exit f vascnstrictr fibers frm the T-10 thrugh the L- level f the spinal crd with the greatest respnse t stimulatin at T-12, T-13, and L-l is in agreement with the earlier studies in the dg by Bayliss and Bradfrd (8) and by Sheehan and Marrazzi in the cat (9) and in the mnkey (10). In the study f the regins f entry f vascnstrictr fibers int the lumbar chain, we were cncerned that all f the fibers leaving the spinal crd might nt be activated by the cartid sinus reflex, since the respnse t electric stimulatin f the lumbar chain usually exceeded that elicited frm the sinus. Hwever, the experiment in which stimulatin f the anterir spinal nerve rts was cmbined with sectin f apprpriate cmmunicating rami cnfirmed the L-, L- level as the last pint f entry int the lumbar chain f the sympathetic vascnstrictr utflw t the hind limb. This last experiment als suggested that all f the vascnstrictr utflws t the limb were activated during maximal stimulatin f the cartid sinus. The upper limits f entry were nt defined because f technical difficulties in expsing the thracic ganglia frm the abdmen, but the cmbined data f Figure suggest that the general pattern f entry int the paravertebral sympathetic chain reflects the pattern f exit frm the spinal crd.

8 178 DONALD, FERGUSON The first pint f exit f vascnstrictr fibers frm the chain was at the L- level, and fibers cntinued t leave at successive caudal levels as far as S-l, the lwest level studied. Thus, the lumbar chain cntained the greatest number f fibers at the L- and L- levels because at this pint all f the fibers had entered the chain but relatively few had left. In an earlier study, Clnninger and Green () reprted that stimulatin f the lumbar chain at L- gave vascnstrictr respnses that exceeded thse btained at ther segmental levels. The data presented here are in accrd with an earlier study by Randall and assciates () in that vascnstrictr respnses were btained frm stimulatin f the lumbar sympathetic chain as far caudal as the sacral level. A difference, hwever, is that in the present study the preganghnic inflw t the lumbar sympathetic trunk f vascnstrictr fibers terminated at L-, L-, whereas these authrs indicated inflws as far caudal as L-7. A pssible explanatin may lie in the relative magnitude f the vascular regins examined in the tw studies, the central ft pad f the dg in the study by Randall and assciates and the vascular bed f the external iliac artery in the present instance. The vessels f the ft pad may represent such a small prprtin f the iliac artery distributin that we were unable t detect alteratins in the caliber f the frmer. The dilatatin bserved n stimulatin f the L-, L-6, and L-7 anterir spinal nerve rts was puzzling, and s far n reasnable explanatin can be ffered. Althugh mvements f the muscles f the hind limb were nt bserved, the pssibility that the vasdilatatin was due t fine fasciculatins deep in the muscles cannt be ruled ut. II. PERSISTENCE OF LOSS OF SYMPATHETIC CONTROL OF HIND-LIMB RESISTANCE VESSELS AFTER UNILATERAL LUMBAR SYMPATHECTOMY (L-2 THROUGH L-7) IN THE DOG T study the extent t which bld flw in active muscles is influenced by the sympathetic nervus system, the bld flw t the hind limbs was measured during graded exercise in trained cnscius dgs whse lumbar paravertebral chain had been remved n ne side frm the L-2 thrugh the L-7 level. Because these animals were studied ver a perid f several weeks, it was necessary t determine if sympathetic vascular cntrl was still absent in the perated limb 1 t 2 mnths after the surgical prcedure. Studies in man (11-1) and dg (1) have suggested that there are functinally significant pathways that d nt traverse the sympathetic chain and that are nt interrupted by sympathetic trunk extirpatin. The present study was undertaken t determine the persistence f sympathetic denervatin because it permitted mre rigrus testing f such denervatin than was pssible in the trained animals referred t abve. Methds II In each f 22 dgs, the right r the left lumbar sympathetic chain was remved intact frm the L-2 thrugh the L-7 level by sterile surgical prcedures. In three dgs, a bilateral lumbar sympathectmy was perfrmed. The persistence f sympathetic denervatin was studied 0 t 77 days after peratin, either by inducing reflex changes in sympathetic vasmtr activity by changing pressure in the islated cartid sinuses (16 dgs), r by electric stimulatin f the anterir spinal nerve rts (9 dgs). Bld flw t the hind limb either was allwed t vary r was held cnstant. Anesthesia and ther techniques emplyed and the measurements f flw and pressure were as described in Methds I. Results Reflexly Induced Changes in Vasmtr Nerve Activity. The averaged data fr each f the 16 dgs are given in Tables 2 and 3. Dgs studied bth under cnditins f varied and f cnstant flw are identified by the same number in each table. In the studies in which the dg perfused its wn limbs (Table 2), bld flw in the denervated limb passively varied directly with reflexly induced changes in artic bld pressure. Flw in the innervated limb either changed very little r

9 BIN SYMPATHETIC VASOCONSTRICTOR OUTFLOWS IN DOG 179 TABLE 2 Changes in Limb Bld Flw Induced by Hypertensin and Hyptensin in Islated Cartid Sinus f the Dg Dg N. f tests Artic pressure (nun Hg) Hyptensin Bld flw Nrmal (ml/min) Denervated Artic pressure (nun Hg) Hypertensin Bld flw (ml/min) Nrmal Denervated Values represent the average change frm cntrl levels in limb flw and artic bld pressure in each dg. varied inversely t that seen in the sympathectmized limb and t the change in artic pressure. These ppsing changes in bld flw are illustrated in Figure 6. When the limbs were perfused at cnstant flw (Table 3), the changes in perfusin pressure in the innervated limbs were similar t thse recrded frm the artic arch. In nine sympathectmized limbs (dgs 1, 3, 7, 8, 11-13, 1, and 16), there was a pressure respnse with CAROTID (mm Hg): i -j 10 r- L Bse Line - _ SINUS N R 0 0 S A / \ / \ \ fs^j\ ) ^-\ small scillatins that were synchrnus with the artic pressure pulses. This slw pressure rise was absent after ligatin f cllateral arterial inflw t the leg. In three dgs (9, 10, and 1) the pressure respnse persisted after ligatin but was reduced r absent after remval f the remaining lumbar sympathetic chain. An example f each class f respnse is shwn in Figure 7. Stimulatin f the Anterir Spinal Nerve Artic Pressure / / / r\ Sympathectmized -^-. ^A / ^ ^_. ~ - _^ /^v / Nrmal / ^ FIGURE 6 30 sec 60 (mm Hg) - 20 Bld jlw in nrmal and sympathectmized hind limb f dg during changes in cartid sinus pressure. : Pressure in cartid sinus was abruptly changed frm 200 t 30 mm Hg. Bld flw in sympathectmized limb (S) passively varied directly with changes in artic pressure (A), while flw in nrmal limb (N) varied inversely. : Cartid sinus pressure was reduced in steps frm 160 t 30 mm Hg. Flw in nrmal limb was relatively unchanged, while flw in sympathectmized limb passively varied directly with changes in artic pressure

10 180 DONALD, FERGUSON TABLE 3 Increase in Artic Pressure and in Limb Pressure (Perfused at Cnstant Flw) when Pressure in Islated Cartid Sinus f the Dg was Decreased frm 200 t SO mm Hg Dg * 10* * 1 16 Mean SD Days after peratin Limb denervated N. f tests Increase in pressure (mm Hg) Arta Nrmal Denervated Respnse in sympathectmized limb still present after ligatin f arterial cllateral but reduced r absent after cntralateral L-2 thrugh L-7 acute sympathectmy Rts. Stimulatin f the anterir spinal nerve rts frm the T-9 thrugh the L-7 level failed t evke any vascnstrictr respnses Cllateral Arteries PRESENT LIGATED Cartid Sinus (mm Hg): (mm Hg) 200 in the hind-limb vessels f the three dgs with bilateral lumbar sympathectmy. Figure 8 shws the changes in perfusin Cllateral Arteries PRESENT LIGATED SYMPATHECTOMY Artic Pressure FIGURE 7 Effect f cartid sinus hypertensin (200 mm Hg) and hyptensin (30 mm Hg) n perfusin pressure in hind limbs (tw dgs) perfused at cnstant flw. : Slw pressure rise in sympathectmized limb (S) during cartid sinus hyptensin ablished by ligatin f cllateral arterial inflw t sympathectmized limb. : Pressure rise in sympathectmized limb during sinus hyptensin reduced by ligatin f cllateral arterial inflw t sympathectmized limb and ablished by remval f lumbar sympathetic chain (L-2 thrugh L-7) n nrmal side (N).

11 SYMPATHETIC VASOCONSTRICTOR OUTFLOWS IN DOG r- I Dg I tf Spinal Rts Dg 2 Nrmal Sympthectmized 80 Spinal Rts Dg 80 FIGURE 8 Changes in limb perfusin pressure in respnse t electric stimulatin f islated anterir spinal nerve rts frm T-9 thrugh L-7 levels. Dgs 1 and 2 had chrnic right lumbar sympathectmy; dgs 3 and had chrnic left lumbar sympathectmy. Vascnstrictr respnses were nt btained in sympathectmized limbs, and stimulatin f anterir nerve rt n ne side did nt evke respnse frm cntralateral limb vessels. Nte slight vasdilatatin n stimulatin f anterir nerve rts in L- thrugh L-7 levels in bth nrmal and sympathectmized limbs. pressure in the fur dgs with unilateral lumbar sympathectmy in which the hind limbs were perfused at a cnstant flw. The changes in bld flw in the self-perfused nrmal and sympathectmized hind limbs during anterir rt stimulatin are shwn in Figure 9. N cnstrictr respnses were btained n the sympathectmized side by stimulating the ipsilateral r cntralateral anterir nerve rts. Discussin In this study the presence r absence f sympathetic vascular cntrl was assessed initially by cmparing, in the nrmal and the surgically sympathectmized hind limb, the vascular respnses evked by reflex excitatin f the sympathetic vascnstrictr nerves. The fllwing were accepted as evidence f vascnstrictin: an increase in perfusin T pressure in a limb perfused at cnstant flw, a decrease in flw in a limb perfused at cnstant pressure, r an unchanged flw in the presence f a sudden increase in perfusin pressure. With these criteria, sympathetic vascnstrictin was judged t be absent in 13 f the 16 dgs studied 0 t 77 days after surgical remval f the lumbar sympathetic chain frm the L-2 thrugh the L-7 level. In the three dgs (9, 10, and 1) in which reflex excitatin f the sympathetic vascnstrictr nerves still elicited increases in perfusin pressure in the sympathectmized limb after interruptin f cllateral arterial inflw t the limb, the pressure changes were ablished r reduced by remving the cntralateral lumbar sympathetic chain. Hwever, when each dg perfused its wn hind limbs, bld flw in the iliac artery f the sympathectmized limb passively varied directly L

12 182 DONALD, FERGUSON Lumbar Sympathectmy Lumbar Sympathectmy STIMULATION OF SPINAL ANTERIOR NERVE ROOTS j 100 Ri 9 hl Lett X u. UJ 0: UJ Q - - * *, * 8 8- UJ O 0. t Uj LIMB FLOW Nrmal Sympalheclmized x AORTIC PRESSURE 9 II 13 I 3 9 II 13 I 3 Thracic Lumbar T L t - FIGURE 9 Changes in bld flw in self-perfused hind limbs (tw dgs) during electric stimulatin f islated thracic and lumbar anterir nerve rts. At each segmental level, change induced in limb bld flw and mean artic pressure was expressed as a percentage f the value bserved befre stimulatin f anterir nerve rt. N vascnstrictr respnses were bserved in sympathectmized limbs. Reductins in bld flw t nrmal limbs were bserved n stimulatin f ipsilateral nerve rts between T-10 and L-3 and T-ll and L-. with induced changes in artic bld pressure and always varied inversely with the change in flw seen in the nrmal limb. In the curse f the experiments n dg 9, there was a perid when large spntaneus fluctuatins in artic bld pressure were bserved. Bld flw in the sympathectmized limb passively varied directly with these changes in artic pressure, but flw in the innervated limb was either unchanged r varied inversely. A reprductin f ne f the recrds made during this phase is shwn in Figure 10. Thus, althugh it seemed that reinnervatin frm the remaining sympathetic chain was taking place in these three dgs, the data shwed that this was nt sufficiently cmplete t allw the same degree f autnmic cntrl f the peripheral vasculature as was bserved n the nrmally innervated side. Barcrft and Hamiltn (16, 17) have suggested that the new pathways resulting frm regeneratin f the sympathetic fibers are functinally less efficient than the riginal. In studies in which the dg perfused its wn leg, the fact that flw in the sympathectmized leg passively varied directly with changes in artic pressure did nt preclude the pssibility that these seemingly whlly passive changes were mdified t sme degree by the sympathetic nerves. The end pint selected fr study was the verall respnse f the hind-limb resistance vessels. Since n attempt was made t study particular regins f the hind limb fr example, skin, islated muscles, r the ft pad the data discussed thus far cannt eliminate the pssibility that sme limited regin may nt have been denervated by L-2 thrugh L-7 sympathectmy. Hwever, the different patterns f respnse in perfusin pressure and bld flw in the nrmal and the sympathectmized limb wuld indicate that if such a regin did exist,

13 SYMPATHETIC VASOCONSTRICTOR OUTFLOWS IN DOG 183 Artic Pressure, (mmhg) LIMB FLOW (ml/min) 20 7 s Sympathectmized 10 2 L N 2 Base Line- Nrmal FIGURE sec Changes in bld flw in self-perfused hind limbs f dg during spntaneus fluctuatins in artic bld pressure. Bld flw in sympathectmized limb passively varied directly with changes in -mean artic pressure, but bld flw in nrmal limb either was relatively cnstant r varied inversely with artic pressure. its vascular bed must be small in relatin t that f the whle limb. In Part I it was shwn that the sympathetic vascnstrictr nerves t the vessels f the dg hind limb left the spinal crd in the T-10 thrugh the L- anterir spinal nerve rts. The mst decisive prf f cmpleteness f sympathectmy thus wuld seem t be affrded by thse studies in which the anterir spinal nerve rts were stimulated frm the T- 9 thrugh the L-7 level. These nine experiments ffered n evidence f neurgenically mediated vascnstrictin in the sympathectmized leg frm either ipsilateral r cntralateral anterir nerve rts. Als, since the rts were stimulated as far caudal as L-7, the data d nt supprt the cntentin that intermediate ganglia in the spinal nerves cntribute t sympathetic peripheral vascular cntrl. Similarly, in a study in man, Barcrft and Hamiltn (16, 17) fund n evidence f any sympathetic nervus cnnectin between the central nervus system and the hands fr 6 mnths after sympathectmy, althugh a year r mre later, vasmtr and sudmtr reflexes had returned in many f the hands. In a study f circulatry changes in the ft after lumbar sympathectmy, Lynn and Barcrft (18) nted that the return f vascular tne was very rapid but that bld flw in the ft was still twice that f the cntrl 3 mnths after sympathectmy. The available data indicated that sympathetic cntrl f the resistance vessels f the hind limb was largely ablished after remval f the lumbar paravertebral chain frm L-2 thrugh L-7, and that neurgenic vascular cntrl was still absent 3 mnths after sympathectmy. Thus, within this 3-mnth perid, a study f the nrmal and the denervated leg in the same animal during exercise shuld prvide evidence f the degree t which bld flw in active muscles was being affected by the sympathetic nervus system. References 1. MEHLER, W. R., FISCHER, J. C, AND ALEXANDER, W. F.: Anatmy and variatins f the lumbsacral sympathetic trunk in the dg. AnatRecll3: 21, 192.

14 18 DONALD, FERGUSON 2. MIZEKES, N. J.: Anatmy f the autnmic nervus system in the dg. Amer J Anat 96: 28, MILLER, M. E.: Anatmy f the dg. Philadelphia, W. B. Saunders C., 196, p RANDALL, W. C, ALEXANDER, W. F., COX, J. W., AND HERTZMAN, A. B.: Functinal analysis f the vasmtr innervatin f the dg's hind ftpad. Circ Res 1: 16, CLONNINCER, C. L., AND GREEN, H. D.: Pathways taken by the sympathetic vasmtr nerves frm the sympathetic chain t the vasculature f the hind leg muscles f the dg. Amer J Physil 181: 28, MOISSEJEFF, E.: Zur Kenntnis des Cartissinusreflexes. Z Ges Exp Med 3: 696, RAWSON, R. O., AND RANDALL, W. C: Cutaneus and muscle vascular respnses t electrical stimulatin f lumbar sympathetic trunk in the dg. Amer J Physil 199: 112, BAYLISS, W. M., AND BRADFORD, J. R.: Innervatin f the vessels f the limbs. J Physil (Lndn) 16: 10, SHEEHAN, D., AND MARRAZZI, A. S.: Sympathetic cmpnent f the sciatic nerve. Prc Sc E.xp Bil Med : 297, SHEEHAN, D., AND MARRAZZI, A. S.: Sympathetic preganglinic utflw t limbs f mnkeys. J Neurphysil : 68, BRONSON, S. R., AND CONSOLE, A. D.: Residual sympathetic pathways after paravertebral sympathectmy. J Neursurg : 23, ALEXANDER, W. F., KUNTZ, A., HENDERSON, W. P., AND EHRLICH, E.: Sympathetic cnductin pathways independent f sympathetic trunks: Their surgical implicatins. J Int Cll Surgens 12: 111, BOYD, J. D., AND MONRO, P. A. C: Partial retentin f autnmic functin after paravertebral sympathectmy (Intermediate lumbar sympathetic ganglia as the prbable explanatin). Lancet 2: 892, KUNTZ, A., AND ALEXANDER, W. F.: Surgical implicatins f lwer thracic and lumbar independent sympathetic pathways. Arch Surg (Chicag) 61: 1007, RANDALL, W. C, ALEXANDER, W. F., HERTZMAN, A. B., Cx, J. W., AND HENDERSON, W. P.: Functinal significance f residual sympathetic pathways fllwing verified lumbar sympathectmy. Amer J Physil 160: 1, BARCROFT, H., AND HAMILTON, G. T. C: Results f sympathectmy f the upper limb: With special reference t Raynaud's disease. Lancet 1: 1, BARCROFT, H., AND HAMILTON, G. T. C: Further bservatins n the results f sympathectmy f the upper limb. Lancet 2: 770, LYNN, R. B., AND BARCROFT, H.: Circulatry changes in the ft after lumbar sympathectmy. Lancet 1: 110, 190.