Synaptic inputs to immunohistochemically identified neurones in the submucous plexus of the XXXX small intestine.

@entity840 @entity6891 @entity6892
1. Electrophysiological recordings were made from neurones in the submucous plexus of the @entity840 small intestine, and these neurones were classified according to their synaptic inputs. 2. The neurones from which recording were made were filled during the recording period with the fluorescent dye, Lucifer Yellow, so they could be re-identified after processing for immunohistochemical localization of vasoactive intestinal peptide ( @entity6891 ). 3. The presence or absence of @entity6891 -like immunoreactivity was determined for a total of 130 neurones whose synaptic inputs had been fully characterized and eighty-two were found to be @entity6891 reactive. After the @entity6891 reactivity had been assessed, the preparations were reprocessed to reveal immunoreactivity for @entity6892 ( @entity6892 ) and a further twenty-three neurones (none of which were reactive for @entity6891 ) were found to be reactive for this peptide. Of the remaining twenty-five neurones, nineteen were not reactive for either @entity6891 or @entity6892 and six could not be re-identified after reprocessing. 4. Electrical stimulation of internodal strands evoked excitatory synaptic potentials lasting 20-30 ms (fast responses) in all but one of the 130 neurones studied. 5. Almost all the @entity6891 -reactive neurones (seventy-eight of eighty-two cells) exhibited inhibitory synaptic potentials, ranging in amplitude from 2 to 30 mV and lasting 150-1500 ms, but few of the @entity6891 -negative neurones had such responses (six of forty-eight cells). No inhibitory synaptic potentials could be evoked in any of the @entity6892 -reactive neurones. 6. Most @entity6891 -reactive neurones (sixty-nine) had a slow excitatory synaptic potential which could be evoked by a single stimulus, lasted 5-20 s and was associated with an increase in input resistance. Only one @entity6892 -reactive neurone had a slow excitatory potential, but such potentials were seen in nine of the nineteen @entity6891 -negative, @entity6892 -negative neurones. 7. In nine of the twenty-three @entity6892 -reactive neurones a single stimulus evoked an excitatory synaptic potential (intermediate excitatory synaptic potential) lasting 500-1500 ms and associated with a fall in the input resistance. None of the @entity6891 -negative, @entity6892 -negative neurones exhibited the intermediate excitatory potentials but it was not possible to determine whether such potentials could be evoked in @entity6891 -reactive neurones because the inhibitory synaptic potentials would obscure such events. 8. It is concluded that neurochemically distinct populations of submucous neurones can be distinguished physiologically on the basis of the differing combinations of types of synaptic input they receive.
