Effects of chronic guanethidine treatment and adrenal medullectomy on plasma levels of catecholamines and corticosterone in forcibly immobilized rats
Kvetnansky, R.; Weise, V.K.; Thoa, N.B.; Kopin, I.J.
Journal of Pharmacology and Experimental Therapeutics 209(2): 287-291
1979
ISSN/ISBN: 0022-3565 PMID: 35604 Document Number: 144713
Chemical sympathectomy by chronic guanethidine treatment attenuated by 70% stress-evoked increases in rat plasma norepinephrine (NE). A deficit in elevation of plasma epinephrine (EPI) and dopamine (DA) became apparent only after 1-2 h of stress. Adrenal medullectomy prevented completely the stress-induced increases in plasma EPI, but decreased plasma NE and DA levels (by 30%) only at early intervals. Combined guanethidine-treatment and adrenal medullectomy abolished almost completely increments in all plasma catecholamines, but neither procedure alone nor the combination altered the stress-evoked increase in plasma corticosterone. Thus, during stress the increment in plasma EPI is derived wholly from the adrenal medulla, whereas most plasma NE is derived from sympathetic nerves. Stress-evoked release of corticosterone was uninfluenced by adrenal medullectomy or guanethidine and therefore appears to be independent of catecholamine release. During the early intervals of prolonged stress the adrenal medulla appears to account for about 30% of the NE and 50% of the DA in plasma, but later the sympathetic nerves appear to supply almost all of these catecholamines. Depletion by guanethidine of EPI and DA is much less than that of NE suggesting that there are extraneuronal sites for storage of EPI and DA and/or that some sympathetic neurons which survive guanethidine treatment are unable to synthesize NE but can take up DA and EPI from the circulation.