title: 5-Hydroxytryptamine is synthesized in neurons terminating in the neural and intermediate lobes of the rat pituitary gland.
abstract: Immunocytochemistry has revealed that nerve fibers within the neural and intermediate lobes of the rat pituitary gland contain 5-hydroxytryptamine (5-HT). Recent anatomical evidence suggests that the content of this amine in the intermediate but not the neural lobe of the pituitary gland may represent 5-HT that has been taken up from the blood rather than synthesized intraneuronally. The purpose of this study was to determine if 5-HT is synthesized in neurons of the neurointermediate lobe of the pituitary gland. 5-HT synthesis was estimated by measuring the accumulation of the 5-HT precursor, 5-hydroxytryptophan (5-HTP), in the neurointermediate lobe of male Long-Evans rats following the administration of NSD 1015, an inhibitor of aromatic L-amino acid decarboxylase. Thirty min following the injection of NSD 1015 (100 mg/kg, i.p.), 5-HTP accumulated in the neurointermediate lobe and the rate of this accumulation was increased by the administration of the 5-HTP precursor, tryptophan, and by electrical stimulation of the pituitary stalk. In addition, repeated injections of the 5-HT uptake inhibitor, fluoxetine (10 mg/kg, i.p., every 12 h for a total of 7 injections), induced a marked depletion of platelet 5-HT but did not alter the concentration of 5-HT in either the neural or intermediate lobes of the pituitary gland. Taken together these results indicate that much of the 5-HT in the neurointermediate lobe of the pituitary gland does not represent 5-HT taken up from the blood, but rather the amine is synthesized in neurons projecting to this region.(ABSTRACT TRUNCATED AT 250 WORDS)
mesh_terms: D006916:5-Hydroxytryptophan / Q000378:metabolism; D000818:Animals; D004295:Dihydroxyphenylalanine / Q000378:metabolism; D004558:Electric Stimulation; D005473:Fluoxetine / Q000494:pharmacology; D006834:Hydrazines / Q000494:pharmacology; D008297:Male; D009474:Neurons / Q000378:metabolism*; D009994:Osmolar Concentration; D010904:Pituitary Gland, Posterior / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D012701:Serotonin / Q000096:biosynthesis*; D012702:Serotonin Antagonists / Q000494:pharmacology
chemical_list: D006834:Hydrazines; D012702:Serotonin Antagonists; D005473:Fluoxetine; D012701:Serotonin; D004295:Dihydroxyphenylalanine; C004297:3-hydroxybenzylhydrazine; D006916:5-Hydroxytryptophan