Figure 1.

PACAP can enhance excitability, rectification and a hyperpolarization-induced rebound depolarization in guinea pig cardiac neurons. Panels A1, B1 illustrate the 20 nM PACAP-induced shift from phasic to multiple action potential generation. Prior to PACAP application, a 1 second, 0.2 nA depolarizing constant current pulse elicited 1 action potential. During exposure to PACAP, the number of action potentials generated by the same depolarizing current pulse increased markedly. Panels A2, B2 show that PACAP also increased the rectification in the hyperpolarization elicited by a 500 second constant current pulse and likewise enhanced the hyperpolarization-induced rebound depolarization. C. Excitability curve showing the PACAP enhancement of action potentials generated by 1 second depolarizing current steps of increasing intensity. Open circles: number of action potentials generated prior to PACAP; closed circles: number of action potentials elicited during exposure to PACAP. Reprinted with permission from the American Journal of Physiology Cell Physiology (Tompkins et al, 2016).