Meeting Abstract

P2.114  Jan. 5  Response of the Amphibian Sympathetic Nervous System To CRF: In Vivo And In Vitro Studies. CARR, J.A.*; BULIN, S.E.; JIANG, L.; Texas Tech Univ., Lubbock james.carr@ttu.edu

In the Texas toad Bufo speciosus we have previously shown that peripheral administration of ovine corticotropin-releasing factor (oCRF) activates the sympathetic nervous system (SNS) and increases pupil dilation, a noninvasive method of gauging changes in SNS activity. In this study we examine the effects of CRF and urocortin on SNS activity in Bufo marinus. We also examine the role of endogenous CRF in mediating SNS activity during stress and whether CRF has a direct action on catecholamine secretion from toad adrenal medullary cells in vitro. oCRF and urocortin (10- 40 µg) both caused a dose dependent increase in pupil dilation when administered peripherally. The low observed effect dose for each peptide was 10 µg, the lowest dose tested. Animals exposed to a brief stressor exhibited an increase in pupil dilation that was associated with increased circulating levels of epinephrine and glucose. Stressor-induced pupil dilation was prevented by propranolol and reduced by alpha-helical CRF, suggesting that any effect of endogenous CRF was secondary to effects on the SNS. For in vitro studies male Bufo speciosus were anesthetized and mixed adrenal/kidney tissue removed and incubated in modified Earle�s Balanced Salt Solution (EBSS) containing one of four oCRF concentrations (0, 0.01, 0.1, 1 µM). After oCRF exposure tissue was incubated briefly in EBSS containing a depolarizing concentration of K+ (60 mM). In low K+ epinephrine (E) secretion exceeded that of norepinephrine (NE) in all treatments. There were no treatment related effects of oCRF on secretion of either catecholamine. Depolarization increased secretion of both catecholamines, although the trend for greater E over NE secretion was reversed. There were no effects of oCRF on E or NE secretion under low or high K+ conditions. These data do not support a direct action of oCRF on adrenal medullary catecholamine secretion in toads.