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Effects of substance P on neurones of the inferior mesenteric ganglia of the guinea‐pig
Author(s) -
Dun N. J.,
Minota S.
Publication year - 1981
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.1981.sp013982
Subject(s) - depolarization , substance p , hyperpolarization (physics) , membrane potential , chemistry , biophysics , sucrose gap , membrane , tetrodotoxin , reversal potential , medicine , resting potential , tris , atropine , endocrinology , neuropeptide , biochemistry , biology , stereochemistry , patch clamp , receptor , nuclear magnetic resonance spectroscopy
1. The membrane effects of substance P on neurones of isolated inferior mesenteric ganglia and the underlying ionic mechanisms were investigated by means of intracellular recording techniques. 2. When applied to the neurones by superfusion, substance P (0.5 μ m ) caused a membrane depolarization; in a few neurones, the depolarization was preceded by a small hyperpolarization. Substance P effects were not altered in a low Ca 2+ /high Mg 2+ solution or in a solution containing d ‐tubocurarine and atropine. 3. When the membrane potential was clamped manually at the resting level between ‐50 and ‐60 mV, substance P caused, in about an equal number of neurones, a slight to moderate decrease and also increase of membrane resistance; a brief increase occurred prior to the decrease of membrane resistance. 4. In neurones with high resting membrane potential (> ‐70 mV), substance P elicited a large depolarization accompanied by a marked increase in membrane resistance; the latter was probably due to anomalous rectification. 5. Conditioning hyperpolarization of the membrane close to the level of E K increased and decreased substance P‐induced depolarization in eleven and two neurones, respectively. 6. Substitution of external Na + with an equimolar amount of either sucrose or Tris buffer markedly attenuated the depolarizing effect of substance P. 7. The substance P‐induced depolarization was diminished in a high K + (10 m m ) solution, and it could be augmented when membrane was hyperpolarized to E K . On the other hand, the effect of substance P was not appreciably affected in a low Cl − solution. 8. It is concluded that substance P depolarizes the sympathetic neurones by increasing and decreasing membrane permeability to Na + and K + , respectively, and that the concomitant membrane resistance change depends on interaction of G Na activation and G K inactivation. 9. The possibility that substance P is the transmitter mediating the non‐cholinergic slow excitatory potential elicited by repetitive preganglionic stimulation in the neurones of the inferior mesenteric ganglia is suggested.