Muscarinic cholinergic receptor binding and electrophysiological response to acetylcholine in cultured rat caudate putamen nucleus neurons

Binding sites with specificity for N-[3H]methylscopolamine ([3H]NMS) are present in homogenates of primary culture neurons from the rat caudate putamen nucleus (CPN). Specific binding is saturable with respect to [3H]NMS. The Scatchard analysis indicates a dissociation constant of 0.6 nM and a density of 7.0 X 10(3) per cell, or 78 fmol/mg protein. In electrophysiological measurements, excitatory postsynaptic currents (EPSCs) in larger cells were increased by pressure application of acetylcholine under voltage clamp condition. The EPSCs may come from neighboring smaller cells with muscarinic acetylcholine receptors.