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Electrical and chemical responsiveness of trigeminal root ganglion neurons of the guinea pig in vitro Spigelman, Igor


Intracellular recording techniques were used to investigate the electrical and chemical membrane properties of neuronal somata in guinea pig trigeminal root ganglion (TRG) slices. All impaled neurons (150) remained quiescent prior to square wave current pulse injection through the intracellular recording electrode. The majority of neurons (≈ 100) exhibited voltage-and time-dependent rectification in response to hyperpolarizing current pulses. Two groups of neurons were distinguished on the basis of action potential characteristics. In one group, action potentials had a plateau (hump) in the repolarization phase. Action potentials evoked from the second group of neurons did not have this characteristic. Average amplitude and duration of spikes and afterhyperpolarizations was larger in the first group of neurons. Bath application of S-glutamate (10⁻²M) caused small (1-2 mV) depolarizations in 2 of 6 neurons tested. These depolarizations were not associated with changes in membrane conductance. 5-hydroxytryptamine (10⁻³ M) produced a small conductance increase and depolarization in 1 of 6 neurons tested. Similar application of 7-aminobutyric acid (GABA; 10⁻⁴-10⁻² M) produced decreases in membrane resistance (up to 63%) associated with membrane depolarization (2-14 mV) in 30 of 36 neurons tested. Reduction of spike amplitude was observed during GABA-mediated depolarization. These investigations suggest that membrane properties of guinea pig TRG neurons are similar to those reported for other mammalian sensory ganglion neurons.

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