Sleep is differently modulated by basal forebrain GABA(A) and GABA(B) receptors

There is evidence that GABA plays a major role in sleep regulation. GABA(A) receptor agonists and different compounds interacting with the GABA(A) rec eptor complex, such as barbiturates and benzodiazepines, can interfere with the sleep/wake cycle. On the other hand, there is very little information about the possible role of GABA(B) receptors in sleep modulation. The nucle us basalis of Meynert (NBM), a cholinergic area in the basal forebrain, pla ys a pivotal role in the modulation of sleep and wakefulness, and both GABA (A) and GABA(B) receptors have been described within the NBM. This study us ed unilateral infusions in the NBM to determine the effects of 3-hydroxy-5- aminomethylisoxazole hydrobromide (muscimol hydrobromide, a GABA(A) recepto r subtype agonist) and beta-(aminomethyl)-4-chlorobenzenepropanoic acid (ba clofen, a GABA(B) receptor subtype agonist) on sleep parameters in freely m oving rats by means of polygraphic recordings. Muscimol (0.5 nmol) and bacl ofen (0.7 nmol) induced an increase in slow-wave sleep and an inhibition of wakefulness. Muscimol, but not baclofen, also caused a decrease in desynch ronized sleep parameters. The results reported here indicate that 1) the NB M activation of both GABA(A) and GABA(B) receptors influences the sleep/wak e cycle, and 2) GABA(A) but not GABA(B) receptors are important for desynch ronized sleep modulation, suggesting that the two GABAergic receptors play different roles in sleep modulation.