Hypothalamic galanin-immunoreactive neurons projecting to the posterior lobe of the rat pituitary: a combined retrograde tracing and immunohistochemical study.
To identify the galanin-immunoreactive neurons projecting to the posterior lobe of the pituitary in the rat hypothalamus, a retrograde tracer (complex of wheat germ agglutinin-enzymatically inactive horseradish peroxidase-colloidal gold) was injected into the posterior lobe of the pituitary. Sections of the hypothalamus were treated with a combination of silver enhancement of retrogradely transported tracer and immunohistochemistry of galanin. Of the total number of hypothalamic cells doubly labeled with retrograde tracing and galanin-immunostaining, 56-60% were found in the supraoptic nucleus, 18-23% in the retrochiasmatic nucleus, 8-10% in the lateral magnocellular portion of the paraventricular nucleus. The ratio of (number of doubly labeled cells/number of galanin-immunoreactive cells) in each of the above regions was similar to the ratio of (number of retrogradely labeled cells/number of Nissl-stained cells) in the supraoptic nucleus. Of all retrogradely labeled cells in the hypothalamus, 51-56% also contained galaninlike immunoreactivity.


CONCLUSIONS
(1) galanin-immunoreactive fibers in the posterior lobe of the pituitary originate mainly in the supraoptic nucleus, retrochiasmatic nucleus, and lateral magnocellular portion of the paraventricular nucleus, (2) most of galanin-immunoreactive cells in these regions project to the posterior lobe of the pituitary, and (3) about half the neurons constituting the hypothalamo-neurohypophyseal system contain galaninlike immunoreactivity.
Arai
R
R
Département de Cytologie, CNRS UA 1199, Université Pierre et Marie Curie, Paris, France.
Onteniente
B
B
Trembleau
A
A
Landry
M
M
Calas
A
A
D000818:Animals; D019004:Galanin; D006735:Horseradish Peroxidase; D007031:Hypothalamus / Q000737:chemistry / Q000166:cytology*; D007150:Immunohistochemistry; D008297:Male; D009474:Neurons / Q000737:chemistry / Q000166:cytology*; D010455:Peptides / Q000032:analysis*; D010902:Pituitary Gland / Q000737:chemistry / Q000166:cytology*; D051381:Rats; D014909:Wheat Germ Agglutinins
D010455:Peptides; D014909:Wheat Germ Agglutinins; D019004:Galanin; D006735:Horseradish Peroxidase