Figure 4.

Commissural muscEPSPs involve the activation of M2, M3, and M4 muscarinic receptors. (A) Representative traces of the effects of the M4-preferring antagonist, tropicamide (A1), and those of the M3-preferring antagonist, 4-DAMP (A2), on muscEPSP induced in control conditions (strychnine/gabazine/DNQX-containing aCSF) and after the washout of the drug (30–45 min). Summary plots of the mean muscEPSP amplitude (A3) and time constant (A4) as a function of the muscarinic antagonist concentration. (B) Traces illustrating the actions of 4-DAMP (B1) and pirenzepine (B2) on depolarizations induced by short-lasting applications of oxotremorine (oxo, 500 μM) in motoneurons synaptically isolated in a TTX/2 mM Mn²⁺-containing aCSF without Ca²⁺. (B3) Summary plot of the mean amplitude of the oxotremorine-induced depolarization in the absence or presence of XE991 and as a function of the different muscarinic antagonist concentrations tested.