title: ACTH-(1-24) and RX 336-M induce excessive grooming in rats through different mechanisms.
abstract: ACTH-(1-24) (0.03-6 micrograms i.c.v.) and RX 336-M (7,8-dihydro-5',6'-dimethylcyclohex-5'-eno-1',2',8',14 codeinone) (1.5-6 mg/kg i.p.) induce dose-related excessive grooming and 'wet-dog' shaking in rats. In the present study, the grooming associated with these compounds was compared and analyzed pharmacologically. Grooming caused by RX 336-M and by ACTH-(1-24) was antagonized when rats were pretreated with comparable doses of morphine (0.5-4 mg/kg s.c.), however, only ACTH-(1-24)-induced grooming was attenuated by naloxone (1 and 10 mg/kg s.c.). ICI 154,129 (N,N-bisallyl-Tyr-Gly-Gly-psi-(CH2S)-Phe-Leu-OH) (30 mg/kg s.c.), a selective delta-opiate receptor antagonist, was ineffective against both ACTH-(1-24) and RX 336-M. Although haloperidol is known to antagonize grooming elicited by ACTH-(1-24) (e.g., Wiegant et al., 1977, European J. Pharmacol. 41, 343), even a high dose of this neuroleptic agent (5 mg/kg s.c.) only partially attenuated grooming caused by RX 336-M. Tolerance developed to the grooming elicited by RX 336-M, and by ACTH-(1-24), but there was no cross-tolerance. Both agents were active in genetically hypotrichotic rats; and, again in such animals, even after numbing the area caudal to the shoulders with lidocaine. Given the divergent results with naloxone, and, possibly, with haloperidol, and the lack of cross-tolerance, we conclude that the excessive grooming induced in rats by ACTH-(1-24) and by RX 336-M is mediated by different mechanisms.
mesh_terms: D000324:Adrenocorticotropic Hormone / Q000031:analogs & derivatives*; D000818:Animals; D000928:Antidepressive Agents / Q000494:pharmacology*; D003061:Codeine / Q000031:analogs & derivatives* / Q000494:pharmacology; D003366:Cosyntropin / Q000494:pharmacology*; D004361:Drug Tolerance; D006120:Grooming / Q000187:drug effects*; D006220:Haloperidol / Q000494:pharmacology; D008297:Male; D009020:Morphine / Q000494:pharmacology; D009270:Naloxone / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D011957:Receptors, Opioid / Q000187:drug effects
chemical_list: D000928:Antidepressive Agents; D011957:Receptors, Opioid; D003366:Cosyntropin; D009270:Naloxone; C006086:RX 336M; D009020:Morphine; D000324:Adrenocorticotropic Hormone; D006220:Haloperidol; D003061:Codeine