Anatomic and physiologic evaluation of a link between the nucleus reticularis gigantocellularis and nucleus ambiguus in the rat

Localized microinjection of wheat germ agglutinin-conjugated horseradish peroxidase into the nucleus ambiguus (NA) of Sprague-Dawley rats retrogradely labeled neurons that were bilaterally located within the confine of the nucleus reticularis gigantocellularis (NRGC). These cells conformed with the Golgi description of cytoarchitectonic configurations and size distributions for neurons in this reticular nucleus. Furthermore, field potentials antidromically evoked at the NA by stimulating the vagus nerve were augmented by concurrent activations of bilateral NRGC sites that were themselves capable of eliciting hypotension and bradycardia. We conclude that the gigantocellular reticular nucleus may at least employ the cardiac vagal preganglionic neurons in the NA to exert its actions on the heart.