BOTH ISO-OSMOTIC AND HYPEROSMOTIC ETHANOL STIMULATE RELEASE OF HYPOTHALAMIC THYROTROPIN-RELEASING-HORMONE DESPITE OPPOSITE EFFECT ON NEURONVOLUME

Previous studies have indicated that isosmolar, but not hyperosmolar, ethanol induces in vitro gonadotropin-releasing hormone secretion from the basal hypothalamus, presumably by causing cell swelling. Moreover , ethanol reduces secretion of another hypothalamic neuropeptide vasop ressin. We have studied the acute effect of ethanol on specific hypoph ysiotropic basal and K+-stimulated thyrotropin-releasing hormone secre tion in vitro especially in relation to cell swelling. Isosmotic 40-16 0 mM ethanol increased thyrotropin-releasing hormone release from the hypothalamic paraventricular nucleus and median eminence in a dose-dep endent manner. Both a 30% decrease of osmolarity and isosmotic 80 mM e thanol induced 12% swelling of hypothalamic neurons. Hyperosmotic 80 m M or 160 mM ethanol induced release of thyrotropin-releasing hormone f rom both hypothalamic structures but did not cause cell swelling (80 m M) or even induced cell shrinkage (160 mM). Depletion of medium Ca2+ d id not affect thyrotropin-releasing hormone secretion caused by either isosmotic or hyperosmotic ethanol. Our data indicate that both iso-an d hyperosmotic ethanol stimulated release of hypophysiotropic thyrotro pin-releasing hormone despite opposite effects on neuron volume. The m echanism of ethanol action appears complex and Variable depending on t he type of cell and neuropeptide affected. (C) 1997 IBRO. Published by Elsevier Science Ltd.