Intracellular recordings and electrophysiological properties of neurons of pancreatic ganglia in vitro

The work was carried out to investigate electrophysiological properties of neurons of cat intrapancreatic ganglia in vitro by means of intracellular recordings. The mean value of resting membrane potential was -58.5 +/- 8.7 mV (chi +/- s chi, n = 35) with a range from -45 to 72 mV. The mean values of membrane input resistance (Rm), time constant (tau) and capacity (Cm) were 68.6 +/- 5.1M omega, 3.4 +/- 0.2 ms and 50.8 +/- 3.9pF (n = 28), respectively. When depolarizing electrotonic potentials induced by intracellular injection of depolarizing current pulses (0.05-0.5nA, 5ms) reached the threshold potential level, all of the neurons could fire action potentials. The threshold, amplitude, overshoot and duration of spikes were 19.2 +/- 0.5mV, 81.0 +/- 1.7mV, 22.6 +/- 0.9mV and 2.9 +/- 0.1ms (n = 35), respectively. The spike was followed by a prolonged after spike hyperpolarization with amplitude of 20.5 +/- 0.8mV (n = 35). In most of neurons, fast excitatory postsynaptic potentials (f-EPSP) or orthodromic action potentials were recorded during stimulation of nerve trunks attached to the intrapancreatic ganglia. The mean values of amplitude, duration of the f-EPSP and conduction velocity of the nerves were 8.9 +/- 0.7mV, 25.8 +/- 1.9ms and 0.48 +/- 0.04m/s (n = 24), respectively. The ongoing synaptic activity was observed in all of cells. Moreover, f-Epsp, was induced by acetylcholine mediated through nicotinic receptors.