Activation of mu opioid receptors in the pre-optic-anterior hypothalamus releases prolactin in the conscious male rat.
Microinjection of opioid agonists into the pre-optic-anterior hypothalamus (PO/AHA) was used to determine the identity of the opioid receptor subtype(s) involved in the stimulation of prolactin release. The mu agonist DAGO [(D-Ala2, NMe-Phe4, Gly-o15)-enkephalin] was the only opioid agonist to show dose-dependent release of prolactin, the lowest significant dose being 0.001 nmoles. Neither the specific delta agonist DPDPE [(D-Pen2, D-Pen5)-enkephalin] nor the specific kappa agonist U50,488H [(trans-3,4-dichloro-N-methyl-N-(2-(1-pyrrodinyl)-cyclohexyl)-benz ene acetamide] showed dose-dependent increase of prolactin secretion, or indeed any significant increase in prolactin secretion in the dose range 0.01-1 nmoles and 0.01-10 nmoles respectively. We suggest that mu (and not kappa or delta) opioid receptors in the PO/AHA are involved in the opioid stimulated release of prolactin in the conscious male rat.
Kapoor
R
R
Centre for Neuroscience, Flinders Medical Centre, South Australia.
Willoughby
J O
JO
D019900:3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; D000818:Animals; D007025:Anterior Hypothalamic Nucleus / Q000187:drug effects / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004399:Dynorphins / Q000494:pharmacology; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; D020881:Enkephalin, D-Penicillamine (2,5)-; D016308:Enkephalin, Leucine-2-Alanine / Q000494:pharmacology; D004745:Enkephalins / Q000494:pharmacology*; D008297:Male; D011301:Preoptic Area / Q000187:drug effects / Q000378:metabolism*; D011388:Prolactin / Q000378:metabolism*; D011759:Pyrrolidines / Q000494:pharmacology; D051381:Rats; D011957:Receptors, Opioid / Q000378:metabolism*; D017450:Receptors, Opioid, mu
D004745:Enkephalins; D011759:Pyrrolidines; D011957:Receptors, Opioid; D017450:Receptors, Opioid, mu; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; D016308:Enkephalin, Leucine-2-Alanine; D019900:3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; D004399:Dynorphins; D020881:Enkephalin, D-Penicillamine (2,5)-; D011388:Prolactin