Morphine, D-Pen2, D-Pen5 enkephalin and U50,488H differentially affect the locomotor activity and behaviours induced by quinpirole in guinea-pigs.
The effects of morphine D-Pen2, D-Pen5 enkephalin (DPDPE) and U50,488H on the behavioural syndrome elicited by the dopamine (DA) D-2 agonist quinpirole, were investigated. Morphine (1, 5 and 15 mg/kg SC) and morphine administered intracerebroventricularly (ICV) (2 x 5 microliters, 10(-3) M; total dose = 10 nmol) produced piloerection and sedation. DPDPE-ICV (2 x 5 microliters and 2 x 10 microliters, 10(-3) M; total doses = 10 and 20 nmol) produced piloerection and sedation similar to morphine. U50,488H (1 mg/kg SC) induced locomotor activity and some stereotyped behaviour, whereas U50,488H (5 and 10 mg/kg SC) induced muscle rigidity and dystonic-like movements. The locomotor and behavioural response elicited by quinpirole (3 mg/kg IP) was attenuated in guinea-pigs pretreated with morphine (1, 5 and 15 mg/kg SC), morphine-ICV (2 x 5 microliters, 10(-3) M), and DPDPE-ICV (2 x 5 microliters and 2 x 10 microliters, 10(-3) M). These effects were reversed by naloxone (15 mg/kg SC). U50,488H (1 mg/kg SC) increased the quinpirole-induced locomotor activity, whereas U50,488H (5 and 10 mg/kg SC) decreased the locomotor activity and stereotyped behaviours produced by quinpirole. These results indicate that the gross behavioural effects of mu, delta and kappa opioids differ in guinea-pigs compared to other rodent species, and suggest differential involvement of these opioid receptor subtypes with DA D-2 receptor-mediated activity.
Brent
P J
PJ
Neuropharmacology Laboratory, Faculty of Medicine, University of Newcastle, NSW, Australia.
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D019900:3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects*; D020881:Enkephalin, D-Penicillamine (2,5)-; D004745:Enkephalins / Q000494:pharmacology*; D004873:Ergolines / Q000494:pharmacology*; D005260:Female; D006168:Guinea Pigs; D006993:Hypnotics and Sedatives / Q000494:pharmacology; D007276:Injections, Intraventricular; D008297:Male; D009020:Morphine / Q000494:pharmacology*; D009043:Motor Activity / Q000187:drug effects*; D010863:Piloerection / Q000187:drug effects; D011759:Pyrrolidines / Q000494:pharmacology*; D019257:Quinpirole
D004745:Enkephalins; D004873:Ergolines; D006993:Hypnotics and Sedatives; D011759:Pyrrolidines; D019257:Quinpirole; D019900:3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; D009020:Morphine; D020881:Enkephalin, D-Penicillamine (2,5)-