Convergence of midbrain, visceral and somatic inputs onto neurons in the nucleus paragigantocellularis lateralis in rats.

Extracellular recordings were made in nucleus paragigantocellularis lateralis (PGL) of the rat in response to stimulation of the dorsal periaqueductoral gray matter (dPAG), ventrolateral periaqueductuctoral gray matter (vPAG), deep peroneal nerve (DPN), median nerve (MN) and great splanchnic nerve (GSPL). Stimulation of dPAG or MN evoked mainly excitatory responses while the responses to stimulation of vPAG were inhibitory. However, stimulation of GSPL or DPN produced both inhibitory and excitatory responses. These neurons were not only responsive to one stimulation site, but were likely responsive to any other stimulation sites. Eighty-nine percent of cells tested (73/82) received convergent inputs from two or more sites. Sixty percent (21/35) of the neurons were identified as cardiovascular units based on their barosensitivity and slow conduction velocities of the descending axons projecting into the spinal cord. This result provided new evidence for the integrative function of neurons in PGL under some circumstances.