Behavioral effects of kappa-opioid-receptor stimulation on neonatal rats.
Previous results show that endogenous opioid systems mediate affective responses in neonatal rats. Opioids modulate isolation-induced ultrasonic vocalizations and analgesia. This study further examines the behavioral effects of kappa-receptor-system stimulation on 10-day-old rats. With the agonist U50,488, response to isolation in terms of vocalizations, activity levels, and pain sensitivity was tested. In contrast to morphine's effects (primarily a mu-agonist), the kappa-agonist U50,488 produced increased vocalizing and hyperactivity, although both opioid agonists caused analgesia. Isolation adds to the U50,488-mediated increase in the latency for paw withdrawal from heat. This study suggests that the kappa system provokes calling and activity as opposed to the quieting effects of mu-agonists found in previous studies. These differential effects may be due in part to the interaction of the opioid and dopamine systems.
Kehoe
P
P
Department of Psychology, Trinity College, Hartford, Connecticut 06106.
Boylan
C B
CB
D019900:3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; D000700:Analgesics / Q000494:pharmacology*; D000818:Animals; D000831:Animals, Newborn; D001143:Arousal / Q000187:drug effects; D001522:Behavior, Animal / Q000187:drug effects*; D001833:Body Temperature Regulation / Q000187:drug effects; D001921:Brain / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D005260:Female; D008297:Male; D009043:Motor Activity / Q000187:drug effects; D009271:Naltrexone / Q000494:pharmacology*; D017288:Pain Threshold / Q000187:drug effects; D011247:Pregnancy; D011759:Pyrrolidines / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D017473:Receptors, Opioid, kappa / Q000187:drug effects*; D012934:Social Isolation; D014828:Vocalization, Animal / Q000187:drug effects
D000700:Analgesics; D011759:Pyrrolidines; D017473:Receptors, Opioid, kappa; D009271:Naltrexone; D019900:3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer