Physiological evidence for alpha 1-adrenergic facilitatory control of the cold-induced TRH release in the rat, obtained by push-pull cannulation of the median eminence.
The alpha-adrenergic antagonists phentolamine and prazosin were administered to male rats to explore their effects on cold-induced TRH release, measured by a chronic push-pull cannula stereotaxically implanted in the median eminence (ME). Phentolamine was given either i.p. (24 or 40 mg/kg), or locally (10(-5) M) in the ME, whereas prazosin was only applied locally (10(-5) M). Phentolamine significantly decreased the cold response (5 +/- 1 pg/15 min vs 21 +/- 5 pg/15 min; P less than 0.02), whatever the administration mode. Moreover, the blocking effect of prazosin directly perfused into the ME (11 +/- 3 pg/15 min vs 26 +/- 9 pg/15 min; P less than 0.05), indicates the specific involvement of alpha 1-adrenergic receptors in the cold-induced TRH response, and points to the ME as a possible site of facilitatory adrenergic control.
Arancibia
S
S
Laboratory of Endocrinological Neurobiology, UA 1197 CNRS, University of Montpellier, France.
Tapia-Arancibia
L
L
Astier
H
H
Assenmacher
I
I
D000818:Animals; D003080:Cold Temperature; D008297:Male; D008473:Median Eminence / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D010646:Phentolamine / Q000494:pharmacology; D011224:Prazosin / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects / Q000502:physiology*; D013973:Thyrotropin-Releasing Hormone / Q000378:metabolism*
D011942:Receptors, Adrenergic, alpha; D013973:Thyrotropin-Releasing Hormone; D011224:Prazosin; D010646:Phentolamine