It is known that ethanol can affect neurotransmitter release and neurosecretion. The mechanisms involved in these effects, however, have not been established. We are studying neurosecretory mechanisms and the effects of ethanol on those mechanisms in several secretory cell types. Mammalian pineal cells have a well defined neuroendocrine function that involves the release of melatonin. We have studied membrane currents in pineal cells acutely dissociated from adult rats using the whole cell patch- clamp technique and found two distinct potassium currents, a slowly activating sustained current similar to the delayed rectifier and a transient current similar to the A current. At normal external calcium concentrations, no calcium or calcium-activated currents were observed. We studied calcium current and calcium-activated chloride current in the ACTH secreting mouse pituitary cell line, AtT-20. We found that the protein kinase c activator l-oleoyl-2- acetylglycerol (OAG) reduced voltage-dependent calcium current, as did the phorbol esters 12-deoxyphorbol-13-isobutyrate and phorbol- 12,13-diacetate. These data suggest that protein kinase C may be an inhibitory regulator of voltage-dependent calcium channels. Analysis of the calcium-activated chloride current revealed that the decay kinetics are largely due to mechanisms that regulate intracellular calcium. The relationship between intracellular calcium and neurosecretion was studied in the catecholamine secreting rat chromaffin cell line, PC12. We found that muscarine- stimulated release of catecholamine is associated with an inositol triphosphate-induced mobilization of intracellular calcium. Ethanol inhibited both the release of neurotransmitter and the increase of intracellular calcium. The significance of the project derives from the fact that the characterization of neurosecretory mechanisms and the actions of ethanol on those mechanisms should increase our understanding of the cellular basis of ethanol's actions in the nervous and endocrine systems.

Agency
National Institute of Health (NIH)
Institute
National Institute on Alcohol Abuse and Alcoholism (NIAAA)
Type
Intramural Research (Z01)
Project #
1Z01AA000479-06
Application #
3817425
Study Section
Project Start
Project End
Budget Start
Budget End
Support Year
6
Fiscal Year
1988
Total Cost
Indirect Cost
Name
Alcohol Abuse and Alcoholism
Department
Type
DUNS #
City
State
Country
United States
Zip Code
Xiong, Keming; Hu, Xiang-Qun; Stewart, Randall R et al. (2005) The mechanism by which ethanol inhibits rat P2X4 receptors is altered by mutation of histidine 241. Br J Pharmacol 145:576-86
Xiong, Keming; Stewart, Randall R; Weight, Forrest F et al. (2004) Role of extracellular histidines in antagonist sensitivity of the rat P2X4 receptor. Neurosci Lett 367:197-200
Xiong, Keming; Stewart, Randall R; Hu, Xiang-Qun et al. (2004) Role of extracellular histidines in agonist sensitivity of the rat P2X4 receptor. Neurosci Lett 365:195-9
Hu, Xiang-Qun; Zhang, Li; Stewart, Randall R et al. (2003) Arginine 222 in the pre-transmembrane domain 1 of 5-HT3A receptors links agonist binding to channel gating. J Biol Chem 278:46583-9
Stewart, R R; Hoge, G J; Zigova, T et al. (2002) Neural progenitor cells of the neonatal rat anterior subventricular zone express functional GABA(A) receptors. J Neurobiol 50:305-22
Wassif, C A; Zhu, P; Kratz, L et al. (2001) Biochemical, phenotypic and neurophysiological characterization of a genetic mouse model of RSH/Smith--Lemli--Opitz syndrome. Hum Mol Genet 10:555-64