INFLUENCE OF A GABA(B) RECEPTOR ANTAGONIST ON THE SLEEP-WAKING CYCLE IN THE RAT

The influence of CGP 35348 (a GABA(B) receptor antagonist) on the slee p-waking cycle was studied in rats. The animals were injected i.p. at the beginning of the light period and the data expressed by 2-h period s and total duration (6 h). At 100 mg/kg, slow-wave sleep (SWS) was de creased during the 6-h recording with a peculiar decrease during the f irst 2 h. SWS was subdivided into three stages: slow-waves; spindles o ccurring as SWS deepens; and intermediate stage appearing prior to par adoxical sleep (PS). Only the slow-wave stage and intermediate stage w ere decreased. Waking was increased during the 6-h recording. It was s ubdivided into waking with hippocampal theta rhythm (psychomotor activ e waking) and waking without theta activity (quiet waking). Both were increased during the first 2 h. However, quiet waking was increased th roughout the recording duration. At 300 mg/kg, SWS was decreased durin g the three 2-h periods. This decrease was principally related to a de crease of the slow-wave stage. PS was increased over the 6-h recording with a marked increase during the second 2-h period. Consequently, un der the influence of the GABA(B) receptor antagonist, the SWS was decr eased at the expense of behavioral stages with cortical tow-voltage ac tivity (waking and PS). GABAergic neurons are present in the mesoponti ne structures responsible for these two stages. We can conclude that e ndogenous GABA acting at the GABA(B) receptor level participates in th e regulation of waking and PS. (C) 1997 Elsevier Science B.V.