Figure 6.

Nitric oxide still has direct effects on motor neuron membrane properties after blockade of adrenoreceptors. A, Intracellular recording from a motor neuron (mn) in the presence of TTX showing voltage deflections in membrane potential after injection of negative current pulses [current monitor (cm)], in control conditions, the presence of 50 μm phentolamine, 200 μm SNAP, and a recover wash, illustrated as five consecutive overlapping traces. A horizontal dotted line is present for comparative purposes and illustrates the reversible effect of SNAP on membrane conductance-resistance. Resting membrane potentials are -68, -70, -68, and -66 mV for control, PHENT, SNAP, and wash, respectively. B, Three-dimensional histogram illustrates the data from one experiment in which the total number of IPSPs with in 30 sec in each condition are separated according on their amplitude. Note, at arrow, that SNAP shifts the amplitude distribution to the right, indicating an increase in the average amplitude of spontaneous IPSPs as a result of an increase in membrane resistance. C, Quantification of the increase in voltage deflection in response to a constant-current pulse (increase in membrane resistance), expressed as a proportion of the corresponding controls (% C). C, Control; P, PHENT, phentolamine; S, SNAP; W, wash; n/s, not significant at p < 0.05; ^**significant at p < 0.05.