ELECTROPHYSIOLOGY, SHAPE, AND CHEMISTRY OF NEURONS THAT PROJECT FROM GUINEA-PIG COLON TO INFERIOR MESENTERIC GANGLIA

Background & Aims: Prevertebral sympathetic ganglia receive inputs fro m intestinofugal neurons, with cell bodies located in the wall of the bowel, Intestinofugal neurons are part of the afferent limbs of intest inointestinal reflexes, The aim of this study was to define the proper ties of intestinofugal neurons using intracellular recordings, Methods : Intestinofugal neurons of the distal colon were retrogradely labeled from the inferior mesenteric ganglia, In whole mounts of the myenteri c plexus/longitudinal muscle of the distal colon, labeled neurons were identified by their fluorescence and recordings were made using biocy tin-filled electrodes, Labeled nerves were characterized immunohistoch emically and morphologically, Results: Intestinofugal neurons were uni axonal neurons with multiple dendrites that had lamellar expansions. T hey were immunoreactive for choline acetyltransferase, Stimulation of nerve fiber tracts elicited large-amplitude excitatory postsynaptic po tentials in all labeled neurons, Some received spontaneous fast excita tory postsynaptic potentials. Those cells that fired action potentials fired only one or two at the start of a depolarizing current pulse, N o intestinofugal neurons had Dogiel type II morphology or a late after hyperpolarizing potential, Conclusions: Intestinofugal neurons are lik ely to be activated by other neurons in the gut wall. They are not AH or Dogiel type II neurons. Thus they seem to be second order neurons i n afferent pathways of intestinointestinal reflexes.