Effect of 5-hydroxytryptophan on prolactin and growth hormone release in the infant rat: evidence for different neurotransmitter mediation.
In 10 day-old female and male rats, administration of 5-hydroxytryptophan (5-HTP) induced a prompt elevation in plasma prolactin (Prl) and growth hormone (GH) levels. Pretreatment with 2 serotonin (5-HT) receptor blockers, methysergide (Meth) and metergoline (MCE), markedly reduced the 5-HTP-induced Prl rise but failed to alter the GH response to 5-HTP. Administration of 2 selective inhibitors of presynaptic 5-HT reuptake, 3-(p-trifluoromethylphenoxy)-N-methyl-3-phenyl-propylamine and chlorimipramine (CIM), potentiated the 5-HTP-stimulated Prl rise but significantly reduced the 5-HTP-induced GH release. Blockade of dopaminergic or alpha-adrenergic receptors by pretreatment with pimozide (Pim) or phentolamine (Phent), respectively, or central sympathectomy by intraventricularly (i.vt.) injected 6-hydroxydopamine (6-OHDA) were capable of reducing the 5-HTP-induced GH release without affecting the 5-HTP-induced Prl rise. These data indicate that in the infant rat the 5-HTP-induced Prl release is mediated via the brain 5-HT system and that a nonspecific activation of the catecholaminergic system is responsible for the GH response to the drug.
D006916:5-Hydroxytryptophan / Q000494:pharmacology*; D000818:Animals; D002997:Clomipramine / Q000494:pharmacology; D005260:Female; D013006:Growth Hormone / Q000378:metabolism*; D006892:Hydroxydopamines / Q000494:pharmacology; D008297:Male; D008711:Metergoline / Q000494:pharmacology; D008784:Methysergide / Q000494:pharmacology; D018377:Neurotransmitter Agents / Q000502:physiology*; D010646:Phentolamine / Q000494:pharmacology; D010647:Phenyl Ethers / Q000494:pharmacology; D010868:Pimozide / Q000494:pharmacology; D010903:Pituitary Gland, Anterior / Q000378:metabolism*; D011388:Prolactin / Q000378:metabolism*; D011437:Propylamines / Q000494:pharmacology; D051381:Rats; D011941:Receptors, Adrenergic / Q000502:physiology*; D011942:Receptors, Adrenergic, alpha / Q000502:physiology*; D011954:Receptors, Dopamine / Q000502:physiology*; D012701:Serotonin / Q000502:physiology; D013268:Stimulation, Chemical; D013565:Sympatholytics / Q000494:pharmacology
D006892:Hydroxydopamines; D018377:Neurotransmitter Agents; D010647:Phenyl Ethers; D011437:Propylamines; D011941:Receptors, Adrenergic; D011942:Receptors, Adrenergic, alpha; D011954:Receptors, Dopamine; D013565:Sympatholytics; D008711:Metergoline; D010868:Pimozide; D012701:Serotonin; D011388:Prolactin; D013006:Growth Hormone; D006916:5-Hydroxytryptophan; D002997:Clomipramine; D008784:Methysergide; D010646:Phentolamine