Nerve terminal degeneration after a single injection of D-amphetaminein iprindoletreated rats: relation to selective long-lasting dopamine depletion

Size: px

Start display at page:

Download "Nerve terminal degeneration after a single injection of D-amphetaminein iprindoletreated rats: relation to selective long-lasting dopamine depletion"

Jade Bond
5 years ago
Views:

1 BE BE BE Exhibit 9 m 378 Brain Research, 291(1984) Elsevier Nerve terminal degeneration after a single injection of D-amphetaminein iprindoletreated rats: relation to selective long-lasting dopamine depletion G. A. RICAURTE, R. W. GUILLERY, L. S. SEIDEN and C. R. SCHUSTER " Department of Pharmacological and Physiological Sciences and Psychiatry, The Universi_ of Chicago, Chicago, IL ( U.S.A. ) (Accepted September 27th. 1983) Key words."amphetamine -- iprindole -- dopamine -- neurotoxicity -- degeneration -- striatum _p A single injection of D-amphetamine has recently been shown to produce long-lasting dopamine (DA) deficits in rats pretreated with iprindole, an agent which interferes with the metabolism of amphetamine and prolongs its half-life. The basis for these persistent DA deficits has,not been determined. The present results suggest that amphetamine produces prolonged DA depletions in iprindoletreated rats by destroying DA nerve terminals. Under certain conditions D-amphetamine appears in fact dopaminergic could not be stated with certainto be toxic to central dopamine (DA) neurons. When ty in that report for two reasons: (1) methamphetaadministered in high doses, amphetamine produces mine produced concomitant long-lasting DA and selong-lasting decreases in DA content and uptaket6, rotonin (5-HT)neurochemical deficits; and (2)meth- When lower amphetamine doses are used but admin- amphetamine was used in high doses. Thus there was istered continuously, similar DA deficits occur ma3 potential for confounding DA terminal degeneration and striatal tyrosine hydroxylase activity is also re- with 5-HT or some other type of terminal degeneraduced on a long-term basis_. Recently, persistent DA tion that might have been produced by the high doses deficits have been produced by a single injection of of methamphetamine employed. amphetamine in rats pretreated with iprindoles.ts. In the present study we have taken advantage of lprindole interferes with the para hydroxylation of the recent discovery that long-lasting DA neuroamphetamine and increases the half-life of ampheta- chemical deficits can be produced with a single dose mine from 1 to approximately 4 h4._4. Thus the con- of amphetamine by administering it in combination tinued presence of amphetamine in brain tissue, with iprindole in order to retard its metabowhether achieved by administering amphetamine in lism 4.5,_4.]5. The aim of this study was to determine high doses, continuously or in combination with whether a single-dose of amphetamine produces iprindole, induces prolonged DA deficits, long-term DA chemical deficits by destroying DA How amphetamine produces these long-lasting nerve fibers. U DA neurochemical deficits has not yet been deter- Male albino Sprague-Dawley rats (Holtzman Co., mined. Studies employing fluorescent histochemical Madison, W1) weighing approximately 250 g were methods _.10have suggested that amphetamine dam- used as subjects. Rats were housed individually in...._., ages DA fibers. The nature of this damage, however, wiremesh cages with free access to food and water in,.::'.z_._.,_._:_<-_:j remains unclear. In a previous reportjl we presented a colonv room where fluorescent lighting was autoevidence of striatal nerve terminal degeneration in matically turned on at h and off at 18.(10 h. rats administered high doses of methamphetamine. Ambient temperature was C. In the first por- However, whether the degenerating terminals were tion of this study groups of rats (n = 5) were adminis- Correspondence: G. A. Rieaurte. Dept. of Pharmacological and Physiological Sciences. The University of Chicago, Chicago, IL U.S.A. ir /84/$03.0(I 1984Elsevier Science Publishers B V.

2 379 tered saline, amphetamine alone, amphetamine in treated with iprindole (10 mg/kg) was confirmed. In combination with iprindole or iprindole alone. In the accord with previous reportss.ts, this amphetamine-isecond portion of this study, groups of rats were ad- prindole treatment produced a long-lasting striatal ministered anaphetamine and iprindole with or with- DA depletion (Table I). This DA depletion was seout amfonelic acid. D-Amphetamine sulfate and lective insofar as 5-HT levels in the striatum, as well iprindole hydrochloride were dissolved in 0.9% sodi- as NE and 5-HT levels in the hippocampus, were not um chloride at a concentration of 9.2 mg/kg and 10 affected on a long-term basis by the same drug treatmg/kg, respectively. Amphetamine and iprindole ment (Table I). were administered concurrently. Amfonelic acid dis- Each of 3 rats treated identically to those showing " solved in a 9:1 (vol./vol.) mixture of propylene glycol a selective striatal DA depletion showed evidence of and 2.5 N K2CO 3 at a concentration of 5 mg/kg was nerve terminal degeneration in the striatum administered immediately after amphetamine and (Fig. 1B). To determine whether the terminal degeniprindole. All drugs were administered intraperito- eration found after amphetamine-iprindole treatneally on a mg/kg basis. Rats for neurochemical ment was dopaminergic, the DA depletion induced studies were killed 2 weeks after drug treatment, by this treatment was blocked with amfonelic acid. Concentrations of DA, 5-HT and norepinephrine This prevented the appearance of striatal terminal I_ (NE) were determined by cation-exchange liquid degeneration after amphetamine-iprindole adminischromatography coupled with electrochemical de- tration. tection. DA and 5-HT measurements were perform- These results strongly suggest that amphetamine ed using the method of Keller et al. 7, as modified in produces a long-lasting striatal DA depletion in iprinthis laboratory'. NE was assayed according to the dole-treated rats by destroying a fraction of striatal method of Fenn et al.l Rats (n = 3 for each group) DA nerve terminals. That the terminal degeneration for degeneration studies were killed 3 days after drug found after amphetamine-iprindole treatment is in treatment since silver impregnation of degenerating fact dopaminergic is suggested by the following facrat nigrostriatal DA terminals is best achieved after a tors: (1) the terminal degeneration is present in rats short survival period Nerve fiber degeneration known to have a selective long-lasting DA deficit studies were performed using the Fink-Heimer (Table I); (2) the terminal degeneration is present in p method 3, as previously described 11. The Fink-Heim- the striatum, a brain region richly innervated by DA er method makes possible selective siiver-impregna- nerve fibers 9 known to be sensitive to the toxic effect tion of degenerating nerve fibers. Fink-Heimer sec- of amphetamines,10._3,16; and (3) appearance of this tions were evaluated for the presence or absence of terminal degeneration is prevented by amfonelic fiber degeneration by an experienced observer who acid, a drug which selectively blocks DA deficits inwasunaware of the treatment conditions, duced by amphetamines in iprindole-treated As a first sltep, the long-lasting effect of ampheta- ratss._2.15. These considerations do not rule out the mine (9.2 mg/kg) on striatal DA content in rats pre- possibility that the degeneration in Fig. 1 is of some TABLE I P Selective Iong-la,_tingstriatal DA depletion after o-amphetamine in iprindole-treated rats Rats were administered o-amphetamine (9.2 mg/kg) immediately after iprindol (10 mg/kg). Rats were killed 2 weeks later and assayed for striatal DA and 5-HT and hippocampal NE and 5-HT. Values are the mean + S.E.M. (n = 5). S Treatment Striatal Hippocampal _, _:,_-,;,. +.:,'.:._a DA (l_g/g) 5-HT (_g/g) NE (l_g/g) 5-HT (ktg/g) Saline 12.9+_ _ o-amphetamine 11.8 _ _ Iprindole _ D-Amphetamine+ iprindole 9.9 _ 0.5* 0.42 _ _0.03 * P < 0.05 Dunnett's test.

3 Fig. 1. Silver-stained sections counter-stained with cresyl violet through the striatum of: A, a control rat, and B, a rat administered amphetamine (9.2 mg/kg) and iprindole (10 mg/kg) 3 days previously. Fine granular argyrophyllic debris indicative of nerve fiber degeneration isevident in the striatum of rat administered amphetamine in combination with iprindole.

4 381 nerve fiber :system which is not dopaminergic but with the presence of striatal nerve terminal degenerwhich is also affected by amphetamine-iprindole ation. It seems reasonable to conclude, therefore, treatment and is also protected by amfonelic acid. that both amphetamine and methamphetamine cause This seems unlikely, however, given the apparent se- prolonged DA deficits by destroying DA terminals. lectivity of both amphetamine-iprindole treatment Of note is that this toxic effect of amphetamines on (Table I) and amfonelic acidl2. DA neurons seems to be restricted to DA terminals DA terminal destruction appears to be an effect since there appears to be no loss of DA cell bodies in produced by amphetamine (or one of its metabolites) the substantia nigra and ventral tegmental area_0.11. itself rather lhan an effect uniquely produced by am- Whether DA toxic changes of the type reported " phetamine-iprindole treatment. The strongest indi- here occur in man as a result of amphetamine abuse is cation of this; is that amphetamine alone also induces not known. Dose, frequency of administration and prolonged DA deficits when administered continu- rate of amphetamine metabolim are some of the variously 10.13or in high doses 16. The primary action of ables that may render man more or less sensitive to iprindole, at least in the present context, seems to be the DA neurotoxic effects of amphetamine. Future to prolong the half-life of amphetamine 4-_4so that an studies will have to ascertain whether amphetamines otherwise innocuous dose of amphetamine (9.2 induce DA toxic changes in man. t_ mg/kg) produces DA toxic changes (Table I and In summary, through the use of combined pharma- Fig. 1). cologicaland morphologicalmethods, this study has This study extends previous reports that ampheta- demonstrated that the long-lasting DA depletion mine damages striatal DA nerve terminals. As noted produced by a single injection of amphetamine in earlier, these reports _._0suggested that amphetamine iprindole-treated rats is due to partial DA nerve fiber damaged DA nerve fibers, but the nature of this destruction. The mechanism underlying DA fiber dedamage was unclear. The present finding of striatal struction by amphetamine remains to be elucidated. terminal degeneration after amphetamine indicates that this damage involves frank DA neuronal de- We are grateful to Pat Cantwell for her patient struction. This study is also in agreement with our help in preparing the manuscript and to S. Price for previous study H, in which evidence of striatal termi- his help with the illustration. G.A.R. is supported by :D nal degeneration was found after high doses of meth- USPHS GM-07190; C.R.S. and L.S. by DA amphetamine. Like amphetamine in this study, and DA L.S. is the recipient of an RSA; MHmethamphetamine in that study produced a long C.R.S. is the recipient of an RSA; DA lasting striatal DA depletion which was correlated 1 Ellison, G., Eison, M. S., Huberman, H. S. and Daniel, F., in rat brain induced by 6-hydroxydopamine: a histological Long-term changes in dopaminergic innervation of caudate and biochemical study, Brain Research, 47 (1972) " nucleus after continuous amphetamine administration, Sci- 7 Keller, R., Arbin, O., Mefford, I. and Adams, R., Liquid ence, 201 (1978) chromatographic analysis of catecholamines: routine assay 2 Fenn, R. J., Siggia, S. and Curran, D. J., Liquid chromato- for regional brain mapping, Life Sci., 19(1976) graphy detector based on single and twin electrode thin-lay- 8 Lucot, J., Horwitz, J. and Seiden, L. S., The effects of p-, er electrochemistry: application to the determination of chloroamphetamine and administration on locomotor accatecholamines in blood plasma, Analyt. Chem., 50 (1978) tivity and serotonin in neonatal and adult rats. J. Pharmai_' Fink, R. P. and Heimer, L., Two methods for the selective col. exp. Ther., 217 (1981) Moore, R. Y. and Bloom, F. E., Central catecholamine silver-impregnation of degenerating axons and their synap- neuron systems: anatomy and physiology of the dopamine tic endings in the central nervous system, Brain Research, 4 system, Ann. Rev. Neurosci., 1(1978) (1967) Nwanze,E. and Jonsson,G., Amphetamineneurotoxicity... _--"_"_4 4 Freeman, J. J. and Sulser, F., Iprindole--amphetamine in- on dopamine nerve terminals in the caudate nucleus of _::,_,_ i teractions in the rat: the role of aromatic hydroxylation of mice, Neurosci. Len., 26 (1981) amphetamine in its mode of action, J. Pharmacol. exp. 11 Ricaurte, G. A., Guillery, R. W., Seiden, L. S., Schuster,,,_ Ther., 183 (1972) C.R. and Moore, R. Y., Dopamine nerve terminal degen- 5 Fuller, R. W. and Hemrick-Luecke, S., Long-lasting deple- eration produced by high doses of methylamphetamine in tion of striatal dopamine by a single injection of ampheta- the rat brain, Brain Research, 235 (1982) mine in iprindole-treated rats, Science, 209 (1980) Schmidt, C. J. and Gibb, J. W., Effect of amfonelic acid on 6 Hedreen, J. C. and Chalmers, J. P., Neuronal degeneration methamphetamine-induced changes in tyrosine hydroxyl-

5 382 ase and tryptophan hydroxylase activity, Soc. Neurosci. 15 Steranka, L., Long-term decreases in striatal dopamine, Abstr., 8 (1982) ,4-dihydroxyphenylacetic acid and homovanillic acid after 13 Steranka, L. R. and Sanders-Bush, E., Long-term effects a single injection of amphetamine in iprindole treated rats: of continuous exposure to amphetamine in brain dopamine time course and time dependent interactions with amfonelconcentration and synaptosomal PharmacoL, 65 (1980) uptake in mice, Europ. J. "-x ic acid, Brain Research, 234 (1982) _,Vagner, G. C. Ricaurte, G. A., Johanson, C. E., Schusf_ 14 Steranka, L. R., Stereospecific long-term effects of am- '----,-_ter, C. R. and Seiden, L. S., Amphetamine induces deplephetamine on striatal dopamine neurons in rats, Europ. J. tion of dopamine and loss of dopamine uptake sites in the Pharmacol., 76 (1981) caudate, Neurology, 30 (1980) v il,

Classes of Neurotransmitters. Neurotransmitters

Classes of Neurotransmitters. Neurotransmitters 1 Drugs Outline 2 Neurotransmitters Agonists and Antagonists Cocaine & other dopamine agonists Alcohol & its effects / Marijuana & its effects Synthetic & Designer Drugs: Ecstasy 1 Classes of Neurotransmitters