Lack of evidence for P2X-purinoceptor involvement in fast synaptic responses in intact sympathetic ganglia isolated from guinea-pigs.

Abstract

Recordings were made from neurons in intact pre- and paravertebral guinea-pig sympathetic ganglia using intracellular microelectrodes. Fast excitatory synaptic responses were evoked by stimulation of preganglionic and peripheral nerve trunks. Suramin (0.1-1 mM) did not affect passive or active membrane properties, nor the amplitude or decay time-course of either synaptic potentials or synaptic currents. Synaptic responses were reversibly reduced in amplitude by hexamethonium (98.7 +/- 0.8%, 50-1000 microM) and d-tubocurarine (95.3 +/- 2.6%, 10-280 microM). ATP (0.5-1 mM) and alpha,beta-methylene ATP (1-40 microM) applied in the bathing solution produced no significant changes in resting membrane potential or input resistance. Prolonged application (up to 25 min) of either compound was also without effect on synaptic responses. These substances also did not affect ganglion cells axotomized one to five days in vivo. These data suggest that activation of P2X-purinoceptors is not involved in the generation of fast excitatory synaptic responses in intact guinea-pig sympathetic ganglia. It appears that dissociation of these neurons must markedly increase their sensitivity to purine nucleotides.