Electrical behaviour of myenteric neurones in the gastric corpus of the guinea‐pig.

Abstract

SUMMARY1. Electrical behaviour of ganglion cells in the myenteric plexus of the guinea-pig stomach was investigated using intracellular recording methods.2. Three subpopulations were identified and classified for convenience of discussion as gastric I, II and III neurones. Gastric I neurones were characterized by repetitive spike discharge during depolarizing current pulses and by higher input resistance than the other types. Gastric II neurones discharged one or two spikes only at the onset of long-lasting depolarizing current pulses. Gastric III neurones did not discharge spikes to depolarizing current pulses and had higher membrane potentials and lower input resistances that the other types. Non-stimulus evoked discharge ('spontaneous' discharge) did not occur in any of the neurones.3. Resting membrane potentials were generated primarily by resting K+ conductance, but were smaller than the estimated K+ equilibrium potential. Analysis based on the constant field equation predicted lower K+ conductance in gastric I than in gastric III neurones. 4. Action potentials in gastric I and II neurones were suppressed or blocked by tetrodotoxin. Spikes that were broadened by tetraethylammonium appeared to have an inward component of Ca2+ current.5. Hyperpolarizing after-potentials were associated with the spikes of both kinds of neurones. These after-potentials had much shorter duration ( < 300 ms) than the post-spike hyperpolarization of AH/type 2 intestinal neurones and unlike intestinal neurones there was no latency between the positive after-potential of the spike and the onset of the hyperpolarization. After-hyperpolarization in the gastric neurones was enhanced when the spikes were broadened by tetraethylammonium and was suppressed by removal of Ca2+ from the bathing solution.6. Treatment with either tetraethylammonium or 4-aminopyridine enhanced excitability and induced 'spontaneously' occurring repetitive spike discharge.7. The electrophysiological behaviour of gastric myenteric neurones differed significantly from intestinal neurones. This was interpreted as specialization of the neural networks that control and co-ordinate the activity of vastly different effector systems in the two regions of the alimentary canal.

Synaptic behaviour of myenteric neurones in the gastric corpus of the guinea‐pig.

“…These values were not significantly different from those for spikes evoked by intrasomal injection of depolarizing current (Schemann & Wood, 1989).…”

“…The scheme described in the preceding paper (Schemann & Wood, 1989) was used to categorize each of the neurones in the study of synaptic events. This scheme used three catagories: (1) gastric I neurones discharged repetitively during intrasomal injection of 100 or 200 ms duration depolarizing current pulses; (2) gastric II neurones discharged one or two spikes only at the onset of the depolarizing current pulses and were therefore deemed to be less excitable than gastric I cells; (3) gastric III neurones in which no action potentials could be evoked by injection of depolarizing current.…”

“…The methods of dissection, intracellular electrical recording, intracellular injection of Lucifer Yellow and application of chemical agents were the same as described in the preceding paper (Schemann & Wood, 1989). Synaptic potentials were evoked by focal electrical stimulation of axons that had synaptic contact with the neuronal cell bodies.…”

Subpopulations of Gastric Myenteric Neurons Are Differentially Activated via Distinct Serotonin Receptors: Projection, Neurochemical Coding, and Functional Implications

“…Impaled myenteric neurons were first classified by their response to intracellular stimulation (rectangular pulses, 0.1-0.3 nA; duration, 300 msec) according to the method of Schemann and Wood (1989). Neurons that responded with more than three action potentials corresponded to gastric I cells; neurons with only one to three action potentials corresponded to gastric II cells.…”

Distribution and trafficking of the μ-opioid receptor in enteric neurons of the guinea pig

“…We did not detect any overlap between MOR-IR and either ChAT or GRP immunoreactivities. Mucosally projecting (NPY-IR) neurons may potentially act as primary afferents, although there is little evidence for gastric neurons with the AH electrophysiological properties, Dogiel Type II morphology, or calbindin labeling characteristic of IPANs in the corpus (7,55,56). There are AH/type II neurons in the gastric antrum, presumably reflecting respective specialized motor activity in these regions (61).…”