Vol. 301, Issue 1, 119-128, April 2002

Role of Protein Kinase C in Control of Ethanol-Modulated -Endorphin Release from Hypothalamic Neurons in Primary Cultures

Alok De¹, Nadka Boyadjieva and Dipak K. Sarkar

Department of Animal Sciences, Rutgers, The State University of New Jersey, Cook College, New Brunswick, New Jersey

We have previously shown that short-term exposure to ethanol stimulates immunoreactive -endorphin (IR--EP) release from hypothalamic neurons and that chronic ethanol exposure decreases the IR--EP release from these neurons. The role of protein kinase C (PKC) in the ethanol-regulated -EP release from hypothalamic neurons has not been established. In this study, by using the primary cultures of hypothalamic neurons, we tested the effects of PKC stimulator phorbol ester 4-phorbol 12-myristate-13-acetate (PMA) and PKC inhibitor chelerythrine chloride on ethanol-induced IR--EP release. Additionally, the effects of ethanol with or without PMA on expression and translocation of various PKC isoenzymes from cytosolic to membrane fraction were determined. PMA treatment increased IR--EP release in a time- and dose-dependent manner. Acute ethanol treatment (3 h) increased, while chronic ethanol treatment (24 h) reduced, the magnitude of PMA-induced IR--EP release. The stimulatory effect of acute ethanol on IR--EP release was reduced by chelerythrine chloride. Determination of the effects of ethanol with or without PMA on seven different PKC isoenzymes (PKC-, -I, -II, -, -, -, and -) revealed that the expression and translocation of only two PKC isoenzymes, PKC- and PKC-, were stimulated by acute treatment with ethanol. Acute ethanol also increased PMA-stimulated expression of these two isoenzymes. Chronic ethanol treatment reduced both basal and PMA-induced increase of PKC- and PKC- expression and translocation. These data provide evidence for the first time that ethanol-regulated IR--EP secretion is controlled by the PKC system, possibly involving PKC- and PKC- isoenzymes.