Introduction Society of Biological Psychiatr~ ~XX)6-3223/98/ PII S (t47~ I

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1 A Novel Pentadecapeptide, BPC 157, Blocks the Stereotypy Produced Acutely by Amphetamine and the Development of Haloperidol-Induced Supersensitivity to Amphetamine Nikola Jelovac, Predrag Sikirid, Rudolf Ru~man, M arijan Petek, Darko Perovid, Pa~ko Konjevoda, Anton Marovid, Sven Seiwerth, Zeljko Grabarevid, Jagoda Sumajstor(fi6, Goran Dodig, and Josip Perid Background: A novel gastric pentadecapeptide, BPC 157, has been shown to attenuate different lesions (i.e., gastrointestinal tract, liver, pancreas, somatosensory neurons). This suggests an interaction with the dopamine system. When used alone, BPC 157 does not affect gross behavior or induce stereotypy. Methods: We first investigated the effect of pentadecapeptitle BPC 157 on stereotypy and acoustic startle response in rats, given as either a prophylactic (1 Ixg/kg IP) or therapeutic (1 ng/kg IP) regimen, with the dopamine indirect agonist amphetamine (1 mg/kg IP). Results: There was a marked attenuation of stereo~pic behavior and acoustic startle response. When the medication was given at the time of maximum amphetamineinduced excitability, there was a reversal of this behavior. A.further focus was on the effect of this pentadecapeptide on increased climbing behavior in mice pretreated with the dopamine antagonist haloperidol (5. mg/kg IP), and subsequently treated with amphetamine (2 mg/kg IP challenge I, 2, 4, and 1 days after haloperidol pretreatment). This protocol is usually used.for the study of behavioral supersensitivio, to the amphetamine stimulating effect. Conclusions: An almost complete reversal was noted when pentadecapeptide was coadministered with haloperidol. Iogether, these data provide compelling evidence.for the interaction of pentadecapeptide BPC 157 with the dopamine system. Biol Psychiatry 1998 Society of Biological Psychiato' Key Words: Pentadecapeptide BPC 157, amphetamine stereotypy, haloperidol-induced amphetamine supersensitivity, pentadecapeptide BPC 157, dopamine system From the Department of Pharmacology, Medical Faculty University of Zagreb. Zagreb, Croatia. Address reprint requests to Predrag Sikiric, MD, PhD, Department of Pharmacology, Medical Faculty University of Zagreb, Salata 11, POB 916, 1 Zagreb, Croatia. Received August 5, 1996; revised February 28, 1997; accepted May 15, Introduction B ecause of the physiologic significance of gut peptides and their possible therapeutic application, there is a particular interest in discovering new peptides, their structure and their mechanisms of action, and especially their interaction with essential physiological systems (Thompson et al 1987; Guglietta 1992). The interaction of particular peptides (e.g., neurotensin, somatostatin) with the dopamine system appears to be of special interest (Hemandez 1986). Pentadecapeptide BPC 157 has been successfully evaluated in various experimental models (Sikirid et al 1993a, 1993b, 1993c, 1994, 1995, 1996a, 1996b, 1997a. 1997b, 1997c). It was synthesized and characterized as an essential fragment, and thought lo be essential for the beneficial activity of an organoprotective protein isolated from human gastric juice (named BPC). This protective property was independently investigated and confirmed by others (Par6 and Kiucyznski 1992; Veljaca et al 1994a. 1994b, 1995a, 1995b; Bosnjak et al 1994; Sandor et al 1996). It apparently has no sequence homology to known gut peptides (Sikiric et al 199'.2, 1993a, 1993b, 1993c, 1994, 1995, 1996a, 1996b, 1997a. 1997b, 1997c). Unlike other peptides, whose beneficial capacity is limited by a short halt-life (Thompson et al 1987; Guglietta 1992), pentadecapeptide BPC 157 appears to be very stable (Sikiric et al 1992, 1993a, 1993b, 1993c. 1994, 1995, 1996a. 1996b, 1997a, 1997b, ]997c). This pentadecapeptide did not show any degradation when incubated in human gastric juice or in water for at least 24 hours (Veljaca et al i 995a). On the other hand, human epidermal growth factor (hegf) and human transforming growth factor (htgf) were stable in water, but rapidly degraded in human gastric juice (e.g., after just 15 min) (Veljaca et al 1995a). Acute toxicology shows a very high therapeutic index, since very high dosages were not accompanied by death or pathologic changes (Sikiric et al 1993b); however, the mechanism of the beneficial action is still not fully understood Society of Biological Psychiatr~ ~XX)6-3223/98/519. PII S6-3223(t47~277- I

2 5 12 BIOL PSYCHIATRY N. Jelovac et al It has recently been suggested that some of the effects of this pentadecapeptide, shown to be present in the gastrointestinal tract and brain, could be mediated by the peripheral and/or central dopamine system (Sikiri6 et al 1993b, 1995, 1997a). Therefore, it was reasonable to further investigate a possible pentadecapeptide BPC 157/ dopamine interaction. For this we chose particular sympathomimetic phenomena thought to be related mainly to the dopaminergic system (Kiraly et al 198; Masuda et al 1991 ; Matin et al 1993). The effect of BPC on dopamine indirect agonist amphetamine-induced stereotypy and acoustic startle response in rats was studied first. This was done as either a prophylactic-cotreatment or therapeutic-salutary regimen (Costall and Naylor 1972; Kiraly et al 198; Matin et al 1993). A further focus was on the effect of this pentadecapeptide on increased climbing behavior in mice pretreated with the dopamine antagonist haloperidol, and subsequently challenged with amphetamine (Masuda et al 1991). This procedure is usually used to study behavioral supersensitivity to the amphetamine stimulating effect. Together, these data provide compelling evidence for a particular interaction of this pentadecapeptide with the dopamine system. Methods and Materials Drugs Pentadecapeptide BPC 157 (Gly-Glu-Pro-Pro-Pro-Gly-Lys-Pro- Ala-Asp-Asp-Ala-Gly-Leu-Val, M.W. I 419) is a partial sequence of human gastric juice peptide BPC freely soluble in water at ph 7. and in saline, prepared as described befi~re (Sikiri6 et al 1993b, 1993c, 1994, 1996a, 1996b, 1997a, 1997b, 1997c) and dissolved in saline. Peptide with 99% (high-performance liquid chromatography) purity (l-des-gly peptide as impurity, biologically inactive) was used. Amphetamine (damphetamine-sulfate, Sigma, St. Louis, MO) was dissolved in saline, whereas haloperidol (Sigma) was dissolved in.1 mol/l tartaric acid to a concentration of 1 mg/ml and further diluted with physiological saline. The injection volumes were 5. ml/kg for rats and 4. ml/kg for mice. Animals Male Wistar Albino rats weighing 2-25 g were used in the experiments. Rats were normally housed in groups of 6, with free access to food and water, in a temperature- and humiditycontrolled room with a 12-hour-light/12-hour-dark cycle. Male NMRI mice weighing 2-22 g were used in the amphetamine hypersensitivity assay. Mice were housed in the colony cage under controlled conditions of light (on at 7:, off at 19:), temperature, and humidity, and allowed free access to the standard laboratory diet and tap water. Experimental Protocol AMPHETAMINE STEREOTYPY AND ACOUSTIC STARTLE RESPONSE. Animals were placed in individual Perspex cages, measuring 3 cm 2 cm 15 cm high, for observation. These were in a soundproofed, diffusely illuminated room maintained at a temperature of 2-22 C. Cardboard screens were placed between the cages to prevent rats being influenced by their neighbors. Rats were placed in the observation cages 3 min before drug treatment to allow adaptation to the new environment (Costal[ and Naylor 1972). All observations were made between 1: and 19: hours by a trained observer who was blind to the drug treatment. The observation period was 12 min after amphetamine injection, and each animal was observed for 1 sec in 5-rain intervals (Marin et al 1993). For the prophylactic regimen, amphetamine was given in a dose of 1 mg/kg IP. Either BPC 157 (1 ~g/kg or 1 ng/kg IP) or saline (5. ml/kg IP) was given simultaneously with the amphetamine. The therapeutic application was designed to investigate the effect of delayed pentadecapeptide application after amphetamine. For this study, either BPC 157 (1 p~g/kg or 1 ng/kg IP) or saline (5. ml/kg IP) were given 6 rain after the administration of amphetamine (1 mg/kg IP). The timing of the pentadecapeptide medication closely corresponds to the time when the intensity of stereotypic behavior should reach maximum. Control groups were treated with.9% NaCI (5. ml/kg IP) simultaneously with amphetamine and/or pentadecapeptide BPC 157. The intensity of stereotypy was assessed by means of the scale proposed by Costall and Naylor (1972), and similarly used in other studies (Ernst 1967; Marin et al 1993). Briefly, the effects were assessed using a scoring system (-4) as follows: ()---the appearance of the animals is the same as saline-treated animals; I--discontinuous sniffing, constant exploratory activity; 2--continuous sniffing and small head movements, periodic exploratory activity; 3--continuous sniffing, discontinuous biting, gnawing, or licking, brief periods of locomotor activity; 4--continuous gnawing, biting, and licking, no exploratory activity. Besides the intensity of stereotypy, the acoustic startle response of the animals was assessed by their reaction to a uniform acoustic stimulus of medium intensity. It was scored by means of a simple scale: --no fear reaction; l--single lwitch; 2--stronger twitching, jumping, and escaping; 3--..violent twitching, panic jumping, and escaping. Haloperidol Pretreatment before Amphetamine Challenges Increased climbing behavior in mice was used as a dopaminergic supersensitivity assay. PRETREATMENT PROTOCOL Haloperidol (5. mg/kg IP) was given either with saline (4. ml/kg IP) or with pentadecapeptide BPC 157 (1 p~g/kg IP or 1 ng/kg IP). Controls animals received an equal volume of saline. AMPHETAMINE CHALLENGE. At suitable intervals after the above-described pretreatment (lst, 2nd, 4th, and 1th postpretreatment days), amphetamine (2 mg/kg IP) was given to all animals (eaclh mouse was used only once in the experiment). Climbing behavior was evaluated as described befi)re (Protais et al 1976). Sixty minutes befbre amphetamine administration,

3 BPC 157 Interacts with DA System 8xoL PSYCHIATRY ;43:5 l stereotyped behavior A C.m 4 3 o--o /..~.-..- *... b--o--o--o--o--o-- """. Time (min) :amphetamine BPC157 saline +12: end of observation E 2 v 1 / "qf"~~ l p<.1, at least, vs. control l (S - 12 rain) --~------_ : amphetamine + saline... t~... amphetamine + BPC157 1 nglkg... *... amphetamine + BPC157 1 lag/kg minutes (-12) Figure 1. Amphetamine stereotypes: prophylactic regimen. Amphetamine was given in a dose of 1 mg/kg body weight IP. BPC 157 (1 I~g/kg or 1 ng/kg body weight IP) or saline (5. ml/kg IP) was given simultaneously with amphetamine. Observation was for 12 rain following amphetamine (time ). Normal animals (saline treated) are not shown (score ). p <.1, at least, vs. amphetamine alone (5-12 min). There were 12 animals for each experimental group. mice were separated into individual cylindrical cages, cm, with a wall of vertical metal bars, 2 mm diameter, 1 cm apart, surmounted by a smooth surface. Immediately after the injection, they were returned to the cages. Ten minutes after the injection, the climbing behavior was scored every 2 min, for 1 rain, according to the following scale: --four paws on the floor; l--clinging to the grids with forepaws; 2~intermittent climbing; 3--essentially uninterrupted climbing. The scores observed during the 1 min were calculated (maximum score 15) and evaluated. Statistical Analysis The stereotypy scores obtained after amphetamine administration at each time point for rats cotreated with saline and those cotreated with BPC 157 (both dosages) were compared using a Kruskal-Wallis analysis of variance (ANOVA) followed by the Mann-Whitney test. The acoustic startle response scores and scores obtained in the climbing assay were compared in the same way. The differences were considered to be significant atp <.1 (downward adjustment because of multiple comparisons) (Dawson-Saunders and Trapp 1994). Results Amphetamine Stereotypy PROPHYLACTIC APPLICATION. Amphetamine induced immediate and prominent stereotypic behavior in all control animals. Rats treated with BPC 157 simultaneously with amphetamine exhibited stereotypies of significantly lower grade. These differences were present throughout the observation period (Figure 1) and were statistically significant at all the observed intervals in rats receiving the higher BPC 157 dosage, whereas no statistical significance was found in rats receiving the lower dosage. The p values, however, were very close to significance at the 6-rain interval, for instance. THERAPEUTIC APPLICATION. When BPC 157 was applied 6 rain after the amphetamine challenge (Figure 2), at the time of the strongest stereotypic behavior, the beneficial effect appears very soon, and seems to be long-lasting. The effect of the higher (~g) dose was

4 514 B1OL PSYCHIATRY N. Jelovac et al stereotyped behavior C 4 3 Time (rain) : amphetamine + 6: BPC167, saline + 12: end of observation E v..a o 2 I p<.1, at least, vs. control (66-12 min) S medication L minutes (-12) --e-- () amphetamine + (+6min) saline () amphetamine + (+6min)BPC 1ng/kg () amphetamine + (+6min)BPC 1pg/kg Figure 2. Amphetamine stereotypes: therapeutic regimen. Amphetamine was given in a dose of 1 mg/kg body weight IP. BPC 157 (1 ixg/kg or 1 ng/kg body weight IP) or saline (5. ml/kg IP) was given 6 min after amphetamine application, at the maximum of amphetamine disturbances. Observation was for 12 rain following amphetamine (time ). Normal animals (saline treated) are not shown (score ). p <.l, at least, vs. amphetamine alone (65-12 min). There were 12 animals for each experimental group. evident after 1 rain and was present until the end of the observation period. The lower (ng) dose had a prominent effect, but its duration seemed to be shorter than the higher dose. This was not substantiated when applied as a cotreatment in the therapeutic regimen. Amphetamine Acoustic Startle Response The excitability of the animals, assessed by their reaction to a uniform acoustic stimulus of medium intensity, was immediately increased after amphetamine application in all control rats. Unlike naive animals (no fear reaction or single twitch), stronger twitching, jumping, and/or even a violent twitching, panic jumping, and escaping were consistently observed in all animals given amphetamine. These disturbances appeared to be quite long-lasting, and were increasingly evident after some period (e.g,, minutes). They continued to be observed until the end of the experiments. PROPHYLACTIC APPLICATION. Rats challenged with amphetamine but cotreated with pentadecapeptide showed an apparently attenuated acoustic startle response as compared with the amphetamine controls. These effects seemed to be evident in both regimens (Figure 3). THERAPEUTIC REGIMEN. When applied during stronger twitching, jumping, and/or even violent twitching, panic jumping, and escaping, the effect of pentadecapeptide is clearly evident in attenuating the abovementioned disturbances. This effect appeared to be prompt and sustained, and could be observed in both high- and low-dose regimens (Figure 4). Effect of Pentadecapeptide on Haloperidol Pretreatment and Subsequent Amphetamine Challenges--Onset and Duration of Supersensitivity to Amphetamine-Induced Increased Climbing Behavior in Mice The course of disturbance observed in our investigation was similar to that already described by others (Costentin et al 1975; Masuda et al 1991). On the 1st day following

5 BPC 157 Interacts with DA System BIOL PSYCHIATRY 515 excitability Time (rain) : amphetamine, BPC, saline + 12: end of observation._m [2 o v 8 O O 1 --e-- amphetamine + saline... ~---- amphetamine + BPC157 1 nglkg...*...- amphetamine + BPC167 1 pglkg ---- saline + saline O minutes (-12) Figure 3. Amphetamine excitability: prophylactic regimen. The excitability of animals was assessed by their reactivity to the uniform acoustic stimulus of medium intensity. Amphetamine was given in a dose of 1 mg/kg body weight 1P. BPC 157 (1 p~g/kg or 1 ng/kg body weight IP) or saline (5. ml/kg IP) was given simultaneously with amphetamine. Observation was for 12 rain following amphetamine (time ). Normal animals (saline treated) did not exhibit any pathologic reaction if subjected to the acoustic stimulus used. p <.1, at least, p,g (1-12 rain) and ng (1 rain, rain) vs. amphetamine alone. There were animals for each experimental group. pretreatment with haloperidol, the supersensitivity, assessed as the increased climbing behavior with amphetamine, was not evident. This is probably due to the antiamphetamine effect of haloperidol itself, which lasts 24 hours (Masuda et al 1991). Of note, on the 2nd and 4th days following pretreatment with haloperidol alone, increased climbing behavior could be regularly noted in all mice after amphetamine challenge (Figure 5). On the contrary, when mice were pretreated with haloperidol and BPC 157, they did not exhibit supersensitivity. Complete reduction was still noted on the 4th day after pretreatment with the higher dose of BPC 157 together with haloperidol. In the ng group, the scores were statistically lower than scores noted in animals pretreated with haloperidol. They were, however, increased in comparison with animals not pretreated with haloperidol (saline pretreatment). The salutary effect of the higher dose also appeared earlier, and it could be clearly seen by the 2nd day. The effect seen on the 2nd and 4th days could not be clearly seen 1 days following the initial haloperidol application. A tendency, however, was still present. Mice pretreated with haloperidol alone appeared to have higher scores than animals pretreated with either dose of BPC 157 with haloperidol, or with saline alone, but this effect was not statistically significant. Discussion When injected in rats, anaphetamine promptly induces characteristic stereotypy (compulsive sniffing, licking, and gnawing) (Costall and Naylor 1972; Kiraly et al 198; Marin et al 1993). Increased climbing behavior was consistently noted in mice pretreated with haloperidol and subsequently challenged with amphetamine (Masuda et al 1991). Pentadecapeptide BPC 157 markedly inhibited these disturbances. Together, these data demonstrate a pentadecapeptide effect. In general, indirectly acting sympathomimetic drugs such as amphetamines have the common property of causing both increased calecholamine release and inhibi-

6 516 BIOL PSYCHIATRY N. Jelovac et al excitability medicatio i (6 min) i O. o.ol M ' p<o.1, at least, vs. control (7-12 rain) I -e-- ()amphetamine + (+6 min) saline... () amphetamine + (+6rain) BPC 1nglkg... * () amphlcramlne + (+6mln) BPC 1pglkg... () saline + (+6 rain) saline I f t I Time (min) : amphetamine + 6: BPC157, saline + 12: end of observation ma, minutes(o-12),,, ~, Figure 4. Amphetamine excitability: therapeutic regimen. Amphetamine was given in a dose of 1 mg/kg body weight IP. BPC 157 (1 ~g/kg or 1 ng/kg body weight IP) or saline (5. ml/kg IP) was given 6 min after amphetamine application, at the maximum of amphetamine disturbances. Observation was for 12 rain following amphetamine (time ). Normal animals (saline treated) did not exhibit any pathologic reaction if subjected to the acoustic stimulus used. p <.1 (7-12 min), at least, vs. amphetamine alone. There were animals for each experimental group. I tion of catecholamine reuptake (primarily dopamine) at nerve endings in the central nervous system (e.g., Parkes 1974; Groves and Rebec 1976; Moore 1967). In this, stereotypic behavior appears to be the result of the activation of the dopaminergic system in the corpus striatum (e.g., Parkes 1974; Randrup and Munkvard 1966, 1967). There is evidence that pentadecapeptide BPC 157 is very effective when applied simultaneously with amphetamine in attenuating stereotypic behavior. This suggests an immediate interference with amphetamine activity. Interestingly, although increased stereotypic behavior may be an indication of already engendered amphetamine activity (e.g., Parkes 1974), this pentadecapeptide is still effective. On the contrary, even a lower dose of the pentadecapeptide (i.e., 1 ng/kg IP) appears to be effective in reducing stereotypic behavior. If applied at the maximum of amphetamine stereotypy, the smaller dose would reverse the otherwise prominent stereotypy as well. Given prophylactically, simultaneously with amphetamine, the ability to effectively counteract the amphetamine stereotypy appears to be limited to the higher dosage; the lower dosage would not reach the level of significance. The inhibiting effect of pentadecapeptide on amphetamine-induced stereotypy appears to be rather specific. Namely, the increased excitability (a strong or violent twitching, panic jumping, and escaping) that appeared in control amphetamine-treated rats after a uniform sound challenge, was reduced by both high and low dosages. This occurred when pentadecapeptide was given either prophylactically as a cotreatment, or later, in an already highly advanced amphetamine disturbance, as a therapeutical medication. In comparison with the effect noted in antagonization of the amphetamine stereotypies, these disturbances could be counteracted with a relatively low pentadecapeptide dosage (particularly in the prophylactic regimen). Importantly, pentadecapeptide BPC 157 alone does not induce stereotypy, nor does it affect gross behavior (Sikiri6 et al 1993b). Although the noted action seems to be clearly consistent, its action is still undefined. A simple conclusion about the possible negative (antagonistic) influence of pentadecapeptide BPC 157 on the dopamine system may be erroneous. Namely, similar findings are not entirely uncommon for dopaminomimetic agents. For instance, in

7 BPC 157 Interacts with DA System BIOL PSYCHIATRY 51'7 18 climbing behavior 16 * p<.1, at least, vs. saline + saline I amphetamine challenge i day 1, day 2, day 4, day 1 j 14 A )< m E 12 PRETREATMENT ] PROTOCOL (day ) ] C E n e- lo -~ 8.o 6 O J e 4-4- L T P l I saline + saline BPC157 1 ng/kg + haloperidol BPCIS7 no ~g/kg + haloperidol haloperidoi q" 4. 1st 2rid 4th 1th days + p<.1, at least, vs ] saline + haloperidol I Figure 5. Haloperidol pretreatment before amphetamine challenges--increased climbing behavior in mice as a dopaminergic supersensitivity assay: pretreatment protocol. Haloperidol (5. mg/kg body weight IP) was given either alone with saline (4. ml/kg body weight IP) or with pentadecapeptide BPC 157 (1 I~g/kg body weight IP or 1 ng/kg body weight IP). Controls animals received simultaneously an equal volume of saline. Amphetamine challenge: At the suitable intervals after the above-described pretreatment (Ist, 2nd, 4th, and 1th post-pretreatment days), amphetamine (2 mg/kg IP) was given to all the animals (each mouse was used only once in the experiment). The scores observed during the 1 rain (in 2-rain intervals) were calculated (maximum score 15) and evaluated, p <.5, at least, vs. corresponding group. There were 6 animals Ibr each experimental group. some studies amantadine, an amphetaminelike agent known to increase dopamine release and synthesis, could antagonize, and did not potentiate stereotypies induced by other dopamine agents, amphetamine or apomorphine. Likewise, given alone, it only slightly affected the gross behavior of animals (Parkes 1974). Thus, an apparently more complex pentadecapeptide BPC 157/dopamine interplay might be suggested. This seems to be the case, particularly regarding the intriguing effect of pentadecapeptide BPC 157 in counteracting increased amphetamine climbing behavior in mice. The increased effect of amphetamine following dopamine antagonist haloperidol application is in line with previous studies (Protais et al 1976; Costentin et al 1975; Masuda et al 1991). Consequently, from a methodological point of view, this could provide an interesting background for further characterization of the pentadecapeptide interaction with dopamine. It is generally believed that increased amphetamine climbing behavior following dopamine antagonist haloperidol application is an end result of striatal dopamine receptor up-regulation. This subse- quently causes the development of amphetamine supersensitivity (Protais et al 1976; Costentin et al 1975; Masuda et al 1991). Thus, if the antagonization of amphetamine stereotypies appears as a result of dopamine antagonist activity (direct or indirect) of the tested pentadecapeptide, a potentiation of the haloperidol effect on amphetamine climbing behavior would be expected. As noted previously in this report, however, the opposite was noted when pentadecapeptide was coadministered with haloperidol. It should be noted that an apparently enhanced amphetamine effect, otherwise very prominent in haloperidol-pretreated mice from the 2nd until the 4th day, consistently disappeared in the pentadecapeptide-cotreated groups in both p~g and ng regimens. Obviously, the noted salutary effect of the pentadecapeptide could hardly be accidental, and suggests a special interaction with striatal dopamine receptors. Since the effect of haloperidol-induced dopamine receptor up-regulation did not appear with 2 days following haloperidol treatment (Masuda et al 1991), it seems likely that pentadecapeptide BPC 157 could have a correspondingly prolonged salutary action, and/or it could

8 5 18 BIOL PSYCHIATRY N. Jelovac et al interfere with early events leading to the later appearance of amphetamine supersensitivity. Although this is not directly related, it should be noted that this pentadecapeptide is stable in gastric juice for at least 24 hours (Veljaca et al 1995a). Besides, its particular interaction with the central dopamine system was also shown in other experimental models (i.e., protection against stress ulcers) (Sikirid et al 1997a). Thus, taken together, these data suggest that this pentadecapeptide could have a modulatory effect on the dopamine system. In the condition of increased dopamine release and synthesis induced by amphetamine, it could both prevent and reverse the consequent disturbances (i.e., stereotypic behavior). Similarly, it could markedly attenuate the consequence of dopamine receptor blockade by haloperidol. This would suggest that this pentadecapeptide modulatory effect also implies, in some way, a substitution of the otherwise prominently insufficient dopamine system, avoiding the subsequent dopamine receptor supersensitivity and raised amphetamine disturbances. Thus, although the suggested special interaction with the dopamine system could be interesting from both theoretical and practical points of view, further studies [i.e., attenuation of neuroleptic catalepsy (report in preparation)] are obviously needed to substantiate the precise site and mechanisms of the evidenced pentadecapeptide/dopamine interplay. Interestingly, it was previously demonstrated that the disturbances induced by reserpine, a depletor of dopaminergic intraneuron granules (Adams and Odunze 1991), and 1-methyl-4-phenyl-l,2,3,6-tetrahydropyridine (MPTP), a parkinsongenic neurotoxin, affecting nigrostriatal dopamine (Adams and Odunze 1991; Heikkila et al 1984), could be markedly prevented and reversed by application of this pentadecapeptide (Sikiri6 et al 1993b). Finally, there is evidence that in addition to eliciting locomotor activity and stereotypy by activation of striatal dopamine receptors (e.g., by amphetamine) (Costall and Naylor 1972; Kiraly et al 198; Masuda et al 1991; Marin et al 1993), this could also be accomplished by removal of glutamatergic excitation in the striatum (for review Kemp 197; Fonnum et al 1981; Lannes et al 1991). Thus, we could speculate that this pentadecapeptide effect might also be related to an interaction with the glutaminergic system. In addition, the noted long-term effect could be explained with activation of a second messenger system. For example, the observed effect may be due to a Ca ++ inflow effect and/or calmodulin activation (Esterle and Sanders-Bush 1991) or glutamyl transpeptidase-like Gs protein activation (Bourne et al 199), presupposing a BPC 157 interaction with the metabotrope N-methyl-Daspartate receptors in the striatum. Interestingly, a similarity between pentadecapeptide BPC 157 and dopamine agent efficacy has already been noticed in gastrointestinal lract protection (Sikiri6 et al 1995). These data should be also viewed as a possible model for screening possibly valuable therapeutic agents for corresponding disturbances [i.e., schizophrenia amphetamine challenge effects (schizophreniform psychoses)] (Connell 1958; Angrist and van Kammen 1984; Wolkin et al 1994; Brauer and de Wit 1996). It might also be used to investigate the importance of known peptides (Thompson et al 1987; Guglietta 1992; Krieger 1983), and their interaction with other neurotransmitter systems, i.e., dopamine (Hernandez 1986). The evidence that BPC 157 does not change the psychopharmacologic profile of normal animals, nor enhance their locomotor behavior (Sikiric et al 1993b), while antagonizing both amphetamine-induced stereotypy and the haloperidol effect, could clearly define pentadecapeptide BPC 157 as an intriguing tool for further experimental and clinical investigation. References Adams JD, Odunze IN (1991): Biochemical mechanisms of l-methyl-4-phenyl-l,2,3,6-tetrahydropyridine toxicity. Biochem Pharmacol 41: Angrist B, van Kammen DP (1984): CNS stimulants as tools in the study of schizophrenia. 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