SYNAPTIC COMMUNICATION BETWEEN EXTERNAL AND INTERNAL SUBMUCOSAL PLEXUS NEURONS IN THE JEJUNUM OF THE NEWBORN PIG

Intracellular recordings were made from neurones in the internal submu cosal plexus (ISP) of porcine small intestine and synaptic inputs were investigated by focal stimulation of nerve fiber tracts. Nicotinic fa st excitatory potentials (e.p.s.p.s) were recorded in all neurones, bu t slow e.p.s.p.s and slow inhibitory potentials (i.p.s.p.s) were rarel y seen. Membrane potential changes similar to those occurring during t he slow e.p.s.p. and slow i.p.s.p. could be evoked by exogenous applic ation of neurotransmitters, even in neurones failing to display a nerv e-mediated response. We suggest that the predominant source of the slo w synaptic inputs to the ISP may be the neurones of the external submu cosal plexus (ESP). The failure to record slow e.p.s.p.s and i.p.s.p.s could be a consequence of the anatomical arrangement of the submucosa l plexuses whereby interconnecting strands between the ISP and ESP are inaccessible to the focal stimulation. (C) 1997 Elsevier Science Inc.