title: Effects of naloxone on the secretion of prolactin and corticosterone induced by 5-hydroxytryptophan and a serotonergic agonist, mCPP.
abstract: The effects of naloxone, an opiate "pure" receptor antagonist, on the release of prolactin and corticosterone in the rat were studied following the administration of the serotonin precursor 5-hydroxytryptophan or the serotonin receptor agonist (-) -m-chlorophenylpiperazine. Naloxone clearly antagonizes the release of prolactin induced by 5-hydroxytryptophan administered alone at a dosage of 50 mg/Kg/b.wt. or at dosage of 30 mg/Kg/b.wt. preceded 60 minutes before injection by the administration of the serotonin uptake blocker fluoxetine. The opiate antagonist does not modify the increase in blood level of prolactin induced by (-) -m-chlorophenylpiperazine. Naloxone itself does not reduce the increase in plasma level of corticosterone induced by 5-hydroxytryptophan, 5-hydroxytryptophan+fluoxetine or (-)-m-chlorophenylpiperazine. The results suggest that endogenous opioids may be involved in the increase in serum level of prolactin induced by 5-hydroxytryptophan and also indicate the existence of different serotonergic neurotransmitter circuits capable of modulating the release of prolactin and corticosterone. A mutual interplay between serotonergic and opiate neurons may be involved in controlling the release of prolactin, but such an interplay does not seem to occur in the secretion of corticotrophin-releasing hormone.
mesh_terms: D006916:5-Hydroxytryptophan / Q000494:pharmacology*; D000818:Animals; D003345:Corticosterone / Q000378:metabolism*; D005473:Fluoxetine / Q000494:pharmacology; D008297:Male; D009270:Naloxone / Q000494:pharmacology*; D010879:Piperazines / Q000494:pharmacology*; D011388:Prolactin / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D010879:Piperazines; D005473:Fluoxetine; D009270:Naloxone; D011388:Prolactin; D006916:5-Hydroxytryptophan; C015068:1-(3-chlorophenyl)piperazine; D003345:Corticosterone