Effect of norepinephrine on the pituitary adrenocorticotrophic activation by ether stress and on the in vitro release of ACTH by the adenohypophysis of male and female newborn rats.
The effect of norepinephrine (NOR) has been investigated in 8-day-old newborn rats of both sexes subjected to stress by 2 min ether inhalation or sham stress. The animals were sacrificed either before or 2 and 32 min after the stress or the sham stress procedure was started. Investigations were also performed on newborns bearing neurotoxic lesions of the arcuate nucleus by neonatal treatment with monosodium-L-glutamate. The effect of NOR was also investigated in vitro on incubated pars distalis. ACTH concentrations in the pituitary, plasma, and the incubation medium were determined by radioimmunoassay. NOR at the dose of 0.2 microgram/g was unable to affect plasma ACTH levels during a period of 60 min in unstressed newborns, in contrast to higher doses (0.5, 1, and 5.0 micrograms/g) which elicited a sharp rise in plasma ACTH levels. Then, NOR was injected (0.2 microgram/g) to male and female pups 15 min before the stress or sham stress procedure. 32 min after the beginning of ether inhalation, the pituitary response was greater in NOR-injected than in saline-injected males; in NOR-treated females the rise in plasma ACTH levels was higher at 2 and 32 min than in saline-injected animals. At this latter time, plasma ACTH levels were similar in NOR-treated males and females, while in saline-treated newborns, the response to ether stress was greater and more longlasting in females than in males. No significant rise in plasma ACTH levels was observed in sham-stressed pups.(ABSTRACT TRUNCATED AT 250 WORDS)
D000324:Adrenocorticotropic Hormone / Q000097:blood / Q000378:metabolism*; D000818:Animals; D000831:Animals, Newborn / Q000378:metabolism*; D001111:Arcuate Nucleus of Hypothalamus / Q000502:physiology; D003346:Corticotropin-Releasing Hormone / Q000494:pharmacology; D004986:Ether; D005260:Female; D066298:In Vitro Techniques; D008297:Male; D009638:Norepinephrine / Q000494:pharmacology*; D010643:Phenoxybenzamine / Q000494:pharmacology; D010903:Pituitary Gland, Anterior / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D012970:Sodium Glutamate / Q000494:pharmacology; D013312:Stress, Physiological / Q000139:chemically induced / Q000378:metabolism*
D004986:Ether; D010643:Phenoxybenzamine; D000324:Adrenocorticotropic Hormone; D003346:Corticotropin-Releasing Hormone; D012970:Sodium Glutamate; D009638:Norepinephrine