beta-Endorphin and gonadotropin-releasing hormone synaptic input to gonadotropin-releasing hormone neurosecretory cells in the male rat.
Physiological and pharmacological evidence has suggested that both endogenous opiates and gonadotropin-releasing hormone (GnRH) itself can act centrally to exert a tonic inhibition on gonadotropin secretion via an inhibition of the neurosecretion of GnRH. To determine if the effects of these two peptides might be mediated via a direct synaptic input to the GnRH neuron, we undertook a double label ultrastructural study. We were able to localize in the same tissue section beta-endorphin and GnRH. Analysis of serial sections through GnRH perikarya and dendrites in the male rat diagonal band/preoptic area revealed that almost 10% of the synapses impinging on the GnRH neuron contained beta-endorphin; an additional 10% of the terminals contained GnRH. These data provide anatomical evidence in support of both a direct modulation of GnRH release by opiates and of the presence of an ultrashort feedback loop.
Chen
W P
WP
Department of Anatomy and Cell Biology, College of Physicians and Surgeons, Columbia University, New York 10032.
Witkin
J W
JW
Silverman
A J
AJ
D000818:Animals; D004723:Endorphins / Q000378:metabolism*; D005625:Frontal Lobe / Q000166:cytology / Q000378:metabolism*; D007150:Immunohistochemistry; D008297:Male; D008854:Microscopy, Electron; D009490:Neurosecretory Systems / Q000033:anatomy & histology / Q000378:metabolism*; D010906:Pituitary Hormone-Releasing Hormones / Q000378:metabolism*; D011301:Preoptic Area / Q000166:cytology / Q000378:metabolism*; D051381:Rats; D011916:Rats, Inbred F344
D004723:Endorphins; D010906:Pituitary Hormone-Releasing Hormones