Interleukin-1β depolarizes magnocellular neurons in the paraventricular nucleus of the hypothalamus through prostaglandin-mediated activation of a non selective cationic conductance

Interleukin-1 beta (IL-1 beta) is involved in hypothalamic regulation of the neuroimmune response by influencing the synthesis and secretion of corticotropin releasing hormone (CRH), vasopressin (VP) and other stress-related mediators. VP secretion from magnocellular (MNC) neurons of the paraventricular nucleus (PVN) of the hypothalamus at the posterior pituitary and/or median eminence contributes to increasing adrenocorticotropin hormone (ACTH) output and ultimately glucocorticoid release, which then contributes to the stress response. fit this study, using whole-cell patch clamp recordings from neurons in a slice preparation of the rat PVN, we show that MNC neurons are also influenced by IL-1 beta. In response to 1 nM IL-1 beta, 62% of MNC neurons tested depolarized (mean depolarization = 10.9 +/- 1.4 mV); effects which were maintained in the presence of a sodium channel blocker, tetrodotoxin (TTX). The effects of IL-1 beta on MNC neurons were blocked in the presence of a specific cyclooxygenase (COX)-2 inhibitor, NS-398, indicating a dependence on prostaglandins (PG) in mediating these effects. In response to direct application of I mu M PGE(2), 57% of MNC neurons depolarized, exhibiting a membrane potential change similar to that induced by IL-1 beta (mean depolarizatioil = 7.8 +/- 1.1 mV). Voltage clamp experiments examining the effects of PGE(2) on the currents evoked by slow voltage ramps revealed activation of a conductance characteristic of a non-selective cationic conductance (NSCC) (voltage-independent, with a reversal potential of -41.8 +/- 7.6 mV), suggesting that this prostanoid directly modifies cationic currents in MNC neurons. These data provide evidence that IL-1 beta depolarizes MNC neurons in the PVN as a result of prostaglandin-mediated activation of a NSCC. (c) 2005 Elsevier B.V. All rights reserved.