Muscarinic inhibition of reticular thalamic cells by basal forebrain neurones.

Pressure injections of a Ringer's solution containing glutamate (10 or 20 mM) into the nucleus basalis of Meynert inhibited the tonic firing of reticular thalamic (RT) neurones which were recorded in rats under deep urethane anaesthesia. When the inhibition was strong enough to stop the discharges, a burst firing mode was induced in RT cells before the recovery of tonic discharges. This glutamate-induced inhibition of RT cells was completely abolished following the systemic administration of the muscarinic antagonist, scopolamine (150 micrograms kg-1, i.v.). These results indicate that the cholinergic cells of the nucleus basalis of Meynert can control the mode of discharges of RT neurones through the activation of muscarinic receptors.