Figure 7.
Inhibition of long-range IPSCs by M2 receptor activation. CNQX, AP-5, and the M1 receptor antagonist pirenzepine are present in the aCSF throughout. A, Voltage-clamp recordings of long-range IPSCs evoked in three different layer II vlEC cells by threshold stimulation of area 35. A1, Effect of muscarine (5 μm) on long-range IPSCs. Left, Control response. Right, After addition of muscarine to the aCSF (A2), application of the M2 antagonist methoctramine (0.8 μm) before muscarine completely blocks the inhibition of long-range IPSCs. Left, Control response in the presence of methoctramine. Right, Response elicited in the presence of methoctramine and muscarine. A3, The muscarinic inhibition of long-range IPSCs is also observed when vlEC cells are recorded with pipettes containing a CS+-based internal solution. Left, Control response. Right, Response elicited in the presence of muscarine. B, Muscarine produces an increase in paired-pulse ratio. B1, Top, Control conditions. Bottom, After addition of muscarine. B2, Same IPSCs as in B1 after scaling of the first IPSC seen in the presence of muscarine to that observed in control conditions. C, Graph plotting the ratio of experimental to control 1/CV2 (y-axis) against the ratio of experimental to control response amplitudes (x-axis). The solid line is a linear fit to the data.