Evidence that hypothalamic periventricular dopamine neurons innervate the intermediate lobe of the rat pituitary.
The purpose of the present study was to provide neurochemical and endocrinological evidence that dopamine (DA) neurons terminating in the intermediate lobe of the rat pituitary originate in the periventricular nucleus of the hypothalamus. One week following surgical separation of the periventricular nucleus from the mediobasal hypothalamus, DA and 3,4-dihydroxyphenyl-acetic acid (DOPAC) concentrations in the intermediate lobe were reduced by 50%, and this was accompanied by an increase in plasma alpha-melanocyte-stimulating hormone (alpha-MSH) concentrations. In contrast, this procedure had no effect on concentrations of prolactin in the plasma, or DA or DOPAC in the median eminence, the region of the mediobasal hypothalamus containing terminals of tuberoinfundibular DA neurons. Electrical stimulation of the periventricular nucleus increased the ratio of DOPAC/DA in the intermediate lobe and reduced the concentrations of alpha-MSH in the plasma, whereas in these same animals the DOPAC/DA ratio in the median eminence and concentrations of prolactin in the plasma were unaltered. These results indicate that approximately 50% of all the DA neurons terminating in the intermediate lobe of the rat pituitary originate in or project through the periventricular nucleus of the hypothalamus, and that these DA neurons regulate the secretion of alpha-MSH from intermediate lobe melanotrophs.
Goudreau
J L
JL
Department of Pharmacology and Toxicology, Michigan State University, East Lansing 48824.
Lindley
S E
SE
Lookingland
K J
KJ
Moore
K E
KE
D015102:3,4-Dihydroxyphenylacetic Acid / Q000378:metabolism; D000818:Animals; D002552:Cerebral Ventricles; D004298:Dopamine / Q000378:metabolism / Q000502:physiology*; D004558:Electric Stimulation; D007031:Hypothalamus / Q000166:cytology / Q000502:physiology*; D007150:Immunohistochemistry; D008297:Male; D008473:Median Eminence / Q000378:metabolism; D009474:Neurons / Q000502:physiology*; D009994:Osmolar Concentration; D010902:Pituitary Gland / Q000166:cytology* / Q000378:metabolism / Q000502:physiology; D011388:Prolactin / Q000097:blood; D051381:Rats; D011919:Rats, Inbred Strains; D000521:alpha-MSH / Q000097:blood
D015102:3,4-Dihydroxyphenylacetic Acid; D000521:alpha-MSH; D011388:Prolactin; D004298:Dopamine