NICOTINIC ACETYLCHOLINE SENSITIVITY OF RAT PETROSAL SENSORY NEURONS IN DISSOCIATED CELL-CULTURE

Using whole-cell, patch-clamp techniques we investigated acetylcholine (ACh) sensitivity of dissociated sensory neurons from rat petrosal ga nglia after 4 h-14 days in vitro. In approx. 68% of petrosal neurons ( PN; n = 109) ACh, applied by fast perfusion or pressure ejection from a 'puffer' pipette, caused a rapid depolarization associated with a co nductance increase. Under voltage clamp near the resting potential (ap prox. -60 mV), ACh induced a hexamethonium-sensitive, inward current ( I-ACh), mimicked by nicotine application, A suggesting the presence of neuronal nicotinic acetylcholine receptors (nAChR). The reversal pote ntial of I-ACh occurred near 0 mV (n = 4), a region where the I-V curv e displayed a prominent rectification. The dose-response relation for I-ACh versus ACh concentration was well fitted by a single exponential with mean (+/-S.E.M.) time constant of 102 +/- 82 ms (n = 6); the des ensitization phase of I-ACh was best fitted by the sum of two exponent ials, with time constant of 870 +/- 210 ms (n = 6) and 8576 +/- 1435 m s (at -70 mV). Fluctuation analysis yielded an apparent single-channel conductance of 21.6 +/- 10 pS (mean +/- S.E.M.; n = 4). These data in dicate that a major subpopulation of sensory neurons in visceral petro sal ganglia of the rat express nAChR. Thus, if similar receptors are p resent on corresponding nerve terminals, they could mediate fast affer ent excitation in response to ACh released at peripheral targets, e.g. , the chemosensory carotid body. (C) 1997 Elsevier Science B.V.