Fig. 2.

NGF modulates synaptic transmission between sympathetic neurons and beating myocytes. A, NGF reversibly potentiates myocyte response to stimulation of a connected neuron. A whole-cell recording was obtained from a neuron visibly connected to a beating myocyte. The neuron was stimulated at 2.5 Hz for a 3 min period (STIM; thin black bars), leading to a small increase in myocyte beat rate under control conditions. After superfusion of 50 ng/ml NGF into the bath solution (10 min) (the break in the timeline indicates that myocyte beat rate was not counted during this perfusion period), the myocyte response to neuronal stimulation was more than doubled. The response to stimulation returned to control levels after washout of the NGF (10 min). B, Magnitude and concentration dependence of synaptic potentiation in NGF. The average myocyte beat rate was measured for a 3 min baseline period before neuronal stimulation and again during the 3 min stimulation. Open bars show the stimulation-evoked elevation in beat rate under control conditions. NGF (10 or 50 ng/ml) was then superfused into the bath, and another 3 min baseline was counted. The neuron was stimulated, and the myocyte beat rate was counted for an additional 3 min period. The black bars show the stimulus-induced elevation in myocyte beat rate in the presence of NGF. 50 ng/ml NGF: significantly different from control, p < 0.002, paired Student’st test, n = 15; 10 ng/ml NGF: not significantly different from control, p < 0.74,n = 7; error bars represent SEM.