Mu- and kappa-opiate receptor control of prolactin secretion in rats: ontogeny and interaction with serotonin.
The present study explores developmental changes in mu- and kappa-opiate receptor control of PRL secretion. The ontogeny of mu- and kappa-receptor function was determined by assessing the PRL response to the mu-agonist sufentanil (SUF) and the kappa-agonist U50488 in 5-, 10-, 15-, 20-, and 60-day-old rats. Both mu- and kappa-agonists stimulated PRL secretion at all ages. The selectivity of the mu- and kappa-agonists was confirmed by selective blockade with their respective antagonists (beta-funaltrexamine and nor-binaltorphimine). Serotonin mediation of opiate-induced changes in PRL secretion was explored across ontogeny by testing cyproheptadine (CYPRO) blockade of agonist responses in 5-, 10-, 20-, and 60-day-old rats. CYPRO attenuated the PRL response to the mu-agonist SUF in 20- and 60-day-old rats, but not in the 5- or 10-day-old pups. CYPRO did not block the kappa-agonist U50488 at any age. Similarly, pretreatment with parachlorophenylalaine lowered the PRL response to SUF in 60-day-old rats, but not in 10-day-old rats. These results support previous reports of a serotonin-mediated mu control of PRL secretion that develops by day 20 and a kappa control of PRL secretion that is independent of serotonin at all ages. These findings also suggest that a previously reported serotonin-independent mu-receptor-mediated control of PRL secretion can be stimulated early in ontogeny.
Blackford
S P
SP
Department of Pharmacology, Duke University Medical Center, Durham, North Carolina 27710.
Little
P J
PJ
Kuhn
C M
CM
D019900:3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; D000375:Aging / Q000502:physiology*; D000818:Animals; D003533:Cyproheptadine / Q000494:pharmacology; D005260:Female; D007700:Kinetics; D008297:Male; D009271:Naltrexone / Q000031:analogs & derivatives / Q000494:pharmacology; D011388:Prolactin / Q000378:metabolism*; D011759:Pyrrolidines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D017473:Receptors, Opioid, kappa / Q000037:antagonists & inhibitors / Q000502:physiology*; D017450:Receptors, Opioid, mu / Q000037:antagonists & inhibitors / Q000502:physiology*; D012701:Serotonin / Q000502:physiology*; D017409:Sufentanil / Q000494:pharmacology
D011759:Pyrrolidines; D017473:Receptors, Opioid, kappa; D017450:Receptors, Opioid, mu; C051843:binaltorphimine; D003533:Cyproheptadine; D012701:Serotonin; D009271:Naltrexone; D019900:3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; C024524:beta-funaltrexamine; D011388:Prolactin; D017409:Sufentanil