The effects of muscarinic cholinergic receptor antagonist on slow bursting neuronal activity in the rat intergeniculate leaflet.

The intergeniculate leaflet (IGL) of the thalamus is an important neuronal element of the mammalian circadian time-keeping system. It receives direct input from retinal ganglion cells. In addition, there are, among other projections, afferents to the IGL from the brainstem cholinergic nuclei. The aim of the present study was to determine the influence of intravenous (i.v.) application of atropine--a muscarinic acetylcholine receptor antagonist, on the ultra-slow isoperiodic oscillations of the IGL neurons. Spontaneous neuronal activity was extracellularly recorded from the rat IGL. Different concentrations of atropine were administrated after recording baseline activity. In all experiments, the period of oscillation became longer after injection of atropine. In some of cases we also noted a temporary disturbance of the oscillatory pattern of neuronal activity. These data suggest that the oscillatory firing of IGL cells can be modulated by cholinergic influence.