CHANGES IN THE SEROTONERGIC SYSTEM DURING THE SLEEP-WAKE CYCLE - SIMULTANEOUS POLYGRAPHIC AND VOLTAMMETRIC RECORDINGS IN HYPOTHALAMUS USINGA TELEMETRY SYSTEM

Changes in the serotonergic system in the posterior hypothalamus of fr eely moving rats were related to sleep and wakefulness using in viva v oltammetry (with carbon fiber microelectrodes) and polygraphic recordi ngs. By using an optoelectronic telemetry system for the voltammetric signals, electrical cross-talk between the two settings was avoided an d simultaneous neurochemical and electrophysiological recordings could be made so that a detailed time course of events could be obtained. E xtracellular levels of the serotonin metabolite, 5-hydroxyindolacetic acid, measured every 2 min, increased with wakefulness and decreased w ith sleep: levels were significantly lower during desynchronized sleep than slow wave sleep. In vivo voltammetry associated with the optoele ctronic telemetry system appears to be a useful tool for studying the relationship between neurochemical changes and electrophysiological ev ents.