Fig. 2.

Histamine induces a higher frequency of evoked APs in neurons from animals with chronic pressure overload. Action potentials were produced by injection of long depolarizing currents (500 ms) prior to (top traces) and after (bottom traces) a 1-s application of histamine. The frequency of APs produced in neurons from sham (A) and chronic pressure overload animals (B) prior to histamine application were not different. However, following exogenous application of histamine, the frequency of APs produced in the PO-treated cell was greater than that observed in neurons from sham tissues. Resting membrane potentials: −42 mV sham, −47 mV PO; current stimulation: 0.5 nA sham, 0.4 nA PO.