LESIONS OF THE NUCLEUS BASALIS MAGNOCELLULARIS DO NOT ALTER THE PROPORTIONS OF PIRENZEPINE-SENSITIVE AND GALLAMINE-SENSITIVE RESPONSES OF SOMATOSENSORY CORTICAL-NEURONS TO ACETYLCHOLINE IN THE RAT

The effects of S-alpha-amino-3-hydroxy-4-isoxozolepropionic acid (AMPA ) lesions of the nucleus basalis magnocellularis on the M1/M2 nature o f the responses of somatosensory cortical neurones to acetylcholine (A Ch) in Sprague-Dawley rats were investigated by iontophoretic applicat ion and extracellular single unit recording, The responses were charac terised using pirenzepine, an M1 receptor antagonist, and gallamine, a n M2 antagonist, Eighty two neurones in control and 94 neurones in les ioned animals were studied. In control animals, 37% of responses to AC h were sensitive to pirenzepine, gallamine or to both antagonists. Thi s increased to 62% in lesioned animals, the proportions of pirenzepine -and gallamine-sensitive responses remaining unchanged. These results provide the first electrophysiological confirmation that bath pirenzep ine-and gallamine-sensitive (M1 and M2) receptors occur postsynaptic t o afferent cholinergic terminals and that their postsynaptic stimulati on may produce both inhibition and excitation. (C) 1998 Elsevier Scien ce B.V.