Muscarinic modulation of high frequency oscillations in pedunculopontine neurons

N. KEZUNOVIC; J. R. HYDE; B. GOITIA; V. BISAGNO; F. J. URBANO; E. GARCIA-RILL

Frontiers in Neurology. Sleep and Chronobiology

Frontiers

Lugar: Lausanne; Año: 2013 vol. 4 p. 1 - 13

1664-2295

We previously reported that persistent application of the non-specific cholinergic agonist carbachol (CAR) increased the frequency of calcium channel-mediated oscillatory activity in pedunculopontine nucleus (PPN) neurons, which we identified as dependent on voltage-gated, high-threshold P/Q-type channels. Here, we tested the hypothesis that M2 muscarinic receptors and G-proteins associated with M2 receptors mediate the increase in oscillatory frequency in PPN neurons. We found, using depolarizing ramps, that patch clamped 9?12 day old rat PPN neurons (nD189) reached their peak oscillatory activity around 􀀀20mV membrane potential. Acute (short duration) application of CAR blocked the oscillatory activity through M2 muscarinic receptors, an effect blocked by atropine. However, persistent (long duration) application of CAR significantly increased the frequency of oscillatory activity in PPN neurons throughM2receptors [401 Hz (with CAR) vs. 231 Hz (without CAR); p <0.001].We then tested the effects of the G-protein antagonist guanosine 50-[b-thio] diphosphate trilithium salt (GDP-b-S), and the G-protein agonist 50-[g-thio] triphosphate trilithium salt (GTP-g-S). We found, using a three-step protocol in voltageclamp mode, that the increase in the frequency of oscillations induced by M2 cholinergic receptors was linked to a voltage-dependent G-protein mechanism. In summary, these results suggest that persistent cholinergic input creates a permissive activation state in the PPN that allows high frequency P/Q-type calcium channel-mediated gamma oscillations to occur.