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Non‐linear membrane properties of sacral sphincter motoneurones in the decerebrate cat
Author(s) -
Paroschy K. L.,
Shefchyk S. J.
Publication year - 2000
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 - 10.1111/j.1469-7793.2000.00741.x
Subject(s) - depolarization , stimulation , urethral sphincter , membrane potential , chemistry , intracellular , hyperpolarization (physics) , urination , anatomy , anesthesia , medicine , endocrinology , neuroscience , biology , urethra , urinary system , biochemistry , organic chemistry , nuclear magnetic resonance spectroscopy
1 Responses to pudendal afferent stimulation and depolarizing intracellular current injection were examined in sacral sphincter motoneurones in decerebrate cats. 2 In 16 animals examined, 2–10 s trains of electrical stimulation of pudendal afferents evoked sustained sphincter motoneurone activity lasting from 5 to >50 s after stimulation. The sustained response was observed in: 11 animals in the absence of any drugs; two animals after the intravenous administration of 5‐hydroxytryptophan (5‐HTP; ≤ 20 mg kg −1 ); one animal in which methoxamine was perfused onto the ventral surface of the exposed spinal cord; and two animals following the administration of intravenous noradrenergic agonists. 3 Extracellular and intracellular recordings from sphincter motoneurones revealed that the persistent firing evoked by afferent stimulation could be terminated by motoneurone membrane hyperpolarization during micturition or by intracellular current injection. 4 Intracellular recordings revealed that 22/40 sphincter motoneurones examined displayed a non‐linear, steep increase in the membrane potential in response to depolarizing ramp current injection. The mean voltage threshold for this non‐linear membrane response was ‐43 ± 3 mV. Five of the 22 cells displaying the non‐linear membrane response were recorded prior to the administration of 5‐HTP; 17 after the intravenous administration of 5‐HTP (≤ 20 mg kg −1 ). 5 It is concluded that sphincter motoneurones have a voltage‐sensitive, non‐linear membrane response to depolarization that could contribute to sustained sphincter motoneurone firing during continence.