Ketamine-induced general anesthesia is compatible with gonadotrophin-releasing hormone pulse generator activity in gonadectomized rats: prospects fordetailed electrophysiological studies in vivo

Previous studies on the mediobasal hypothalamus (MBH) of rats, rhesus monke ys and goats have detected episodic increases in multiunit activity (MUA vo lleys) which immediately precede a pulse of luteinizing hormone (LH). These volleys are considered to reflect the activity of the gonadotropin-releasi ng hormone (GnRH) pulse generator. Our understanding of this system would b e greatly enhanced if it were possible to study the electrophysiological as pects of this system at the single cell level; such an approach requires an esthesia of the animals (as in the classic studies on the oxytocin and vaso pressin systems). Although it is widely held that anesthetic agents disrupt the processes regulating LH release, little is known about their specific effects on the dynamics of this system. Using on-line electrophysiological techniques in addition to subsequent radioimmunoassay for LH, we have found that anesthesia by ketamine is compatible with the continued production of MUA volleys and LH pulses in gonadectomized rats. In contrast to the hypot hermia induced by the LH pulse-suppressing anesthetic sodium pentobarbitone , a small rise in core temperature occurs following ketamine. The present f indings offer the prospect of detailed electrophysiological analysis of GnR H pulse generator activity in rats maintained under general anesthesia. (C) 1999 Published by Elsevier Science B.V. All rights reserved.