Direct activation of guinea pig vagal afferent neurons by FMRFamide.

Vagus nerve comprises two distinct kinds of nerves, nodose and jugular ganglionic nerves. We tested pharmacological difference between two vagal nerves in the responsiveness to FMRFamide. The response probability to FMRFamide was significantly higher in nodose than jugular nerves in intracellular calcium measurement. Nodose nerves also depolarized membrane potential to FMRFamide more than jugular nerves did, in patch-clamp recording, although the probability of action potential discharge was same in both nerves. The inward current induced by FMRFamide was characterized as mixed cations. These results suggest that FMRFamide may act as an activator and modulator of vagal sensory nerves for treating symptoms in visceral diseases.