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The effects of physostigmine on synaptic transmission in the inferior mesenteric ganglion of guinea‐pigs
Author(s) -
Bornstein J. C.
Publication year - 1974
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1974.sp010658
Subject(s) - physostigmine , neurotransmission , atropine , depolarization , acetylcholine , chemistry , electrophysiology , stimulation , cholinesterase , neuroscience , anesthesia , biophysics , biology , endocrinology , medicine , biochemistry , receptor
1. Synaptic potentials were recorded with intracellular electrodes from cells in the inferior mesenteric ganglion of the guinea‐pig. 2. Half‐widths of the synaptic potentials recorded fell into two groups: type L cells had long synaptic potentials (11·6–15·2 msec) and low thresholds (14·6 mV mean), type S cells had short synaptic potentials (6·1–9·3 msec) and high thresholds (29·9 mV mean). 3. Physostigmine (1·2 × 10 −6 M ) caused a significant increase in the half‐width of both types of synaptic potential. 4. Physostigmine caused a significant increase in the half‐width of spontaneous synaptic potentials and an increase in their amplitude. 5. Repetitive preganglionic stimulation, in the presence of physostigmine, led to a marked and prolonged depolarization in all cells. In most cells repetitive spontaneous firing of action potentials was then observed. This effect was blocked by atropine (1·4 × 10 −7 M ). 6. The effect of atropine on the half‐width in a physostigmine‐treated cell was inconsistent: although synaptic potentials in some cells were slightly shortened their half‐widths were always greater than the control. 7. It is concluded that cholinesterase plays a role in limiting the time course of the synaptic potential, by limiting the duration of action of acetylcholine.