Paradoxical elevation of growth hormone by intraventricular somatostatin: possible ultrashort-loop feedback.
Somatostatin, the growth hormone-inhibiting factor, when microinjected into the third ventricle of the rat brain, paradoxically induced the release of growth hormone. A pituitary site of action having been ruled out, this result supports the concept that exogenous somatostatin within the hypothalamus acts either to suppress the release of somatostatin from somatostatin-containing neurons, possibly via an ultrashort-loop feedback mechanism, or to augment release of hypothalamic growth hormone-releasing factor, thereby inducing a release of growth hormone. Injection of somatostatin into the third ventricle also decreased plasma concentrations of luteinizing hormone, follicle-stimulating hormone, and thyroid-stimulating hormone, probably by inhibiting the release of luteinizing hormone-releasing factor and thyrotropin-releasing factor.
D000818:Animals; D002369:Castration; D005260:Female; D005640:Follicle Stimulating Hormone / Q000097:blood; D013006:Growth Hormone / Q000378:metabolism*; D007031:Hypothalamus / Q000187:drug effects* / Q000378:metabolism; D007276:Injections, Intraventricular; D007986:Luteinizing Hormone / Q000097:blood; D008657:Metabolic Clearance Rate; D051381:Rats; D013004:Somatostatin / Q000008:administration & dosage / Q000494:pharmacology*; D013972:Thyrotropin / Q000097:blood; D013997:Time Factors
D013004:Somatostatin; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone; D013972:Thyrotropin; D013006:Growth Hormone