Stress suppression of growth hormone secretion in the rat: effects of disruption of inhibitory noradrenergic afferents to the median eminence.
The participation of a growth hormone (GH) inhibitory noradrenergic input to the median eminence in stress-induced suppression of rat GH secretion was investigated in animals with median eminence catecholamine lesions produced by intravenous injection of 6-hydroxydopamine (6-OHDA). Unstressed lesioned rats exhibited an enhanced frequency of GH secretory bursts, but both intact and lesioned rats responded to stress with suppression of GH (controls: 56% suppression, 6-OHDA lesioned: 43% suppression, not significantly different). Thus noradrenergic projections to the median eminence, if they participate at all in stress-induced GH suppression, appear to have only a minor role. This study does not exclude the possibility that circulating adrenaline of adrenal medullary origin might obscure defects in GH control produced by noradrenergic denervation of the median eminence.
D000344:Afferent Pathways / Q000503:physiopathology*; D000818:Animals; D013006:Growth Hormone / Q000378:metabolism*; D006892:Hydroxydopamines / Q000633:toxicity; D008297:Male; D008473:Median Eminence / Q000503:physiopathology*; D008856:Microscopy, Fluorescence; D009638:Norepinephrine / Q000502:physiology*; D016627:Oxidopamine; D011863:Radioimmunoassay; D051381:Rats; D011919:Rats, Inbred Strains; D013312:Stress, Physiological / Q000503:physiopathology*
D006892:Hydroxydopamines; D016627:Oxidopamine; D013006:Growth Hormone; D009638:Norepinephrine