The Journal of Neurophysiology Vol. 87 No. 6 June 2002, pp. 2801-2807
Copyright ©2002 by the American Physiological Society

Chemical Communication Between Vagal Afferent Somata in Nodose Ganglia of the Rat and the Guinea Pig In Vitro

Department of Pharmacology and Experimental Therapeutics, University of Maryland, School of Medicine, Baltimore, Maryland 21201-1559

Oh, Eun Joo and Daniel Weinreich. Chemical Communication Between Vagal Afferent Somata in Nodose Ganglia of the Rat and the Guinea Pig In Vitro. J. Neurophysiol. 87: 2801-2807, 2002. The cell bodies of spinal afferents, dorsal root ganglion neurons, are depolarized several millivolts, and their probability of spiking increased when axons of neighboring somata in the same ganglion are electrically stimulated repetitively. This form of neural communication has been designated cross-depolarization (CD) and cross-excitation (CE). The existence of CD and CE between somata of vagal afferents (nodose ganglion neurons, NGNs) of rats and guinea pigs was investigated by electrically stimulating the vagus nerve while recording the electrical activity of NGNs in intact nodose ganglia with sharp intracellular microelectrodes. CD and CE in NGNs were manifested by a membrane depolarization (~4 mV), the presence of spontaneous action potentials, and a decreased spike threshold. CD was dependent on the frequency and intensity of vagal nerve stimulation. Two distinct types of CD were observed: 1) in NGNs with large input resistances (R_in), CD was dependent on [Ca²⁺]_o, associated with increased membrane conductance, and had an extrapolated reversal potential (E_rev) value of about 25 mV; and 2) in NGNs with low R_in, CD was independent of [Ca²⁺]_o, not accompanied by a membrane conductance change, or a measurable E_rev value. These data reveal the existence of a chemical communication pathway between vagal afferent somata and suggest the possibility that communication between different visceral organs may occur at the level of the primary vagal afferent neuron.