title: Activation of opioid receptors in the mediobasal hypothalamus stimulates prolactin secretion in the conscious rat.
abstract: Abstract In an attempt to localize the opioid receptor(s) (mu, delta and kappa) involved in opioid-stimulated prolactin release in the conscious male rat, opioid agonists were microinjected into the mediobasal hypothalamus and prolactin levels measured before and after injection. The specific mu agonist, DAGO ((D-Ala(2), NMe-Phe(4), Gly-ol(5))-enkephalin) was the most effective in eliciting prolactin release, the smallest effective dose being 0.01 nmoles. The specific delta agonist, DPDPE ((D-Pen(2), D-Pen(5))-enkephalin) had no significant effect even at the highest dose of 10 nmoles. The specific kappa agonist, U50,488H ((trans-3,4-dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzene acetamide) was effective at the doses 1.0 and 10 nmoles. We conclude that mu and kappa opioid receptors in the mediobasal hypothalamus are involved in opioid-stimulated prolactin release and that delta receptors are not.
authors.affiliation: Centre for Neuroscience and Department of Medicine, Flinders Medical Centre, Bedford Park, South Australia, 5042.
authors.forename: R
authors.initials: R
authors.lastname: Kapoor
authors.forename: J O
authors.initials: JO
authors.lastname: Willoughby