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Title

Effect of vasopressin on the input-output properties of rat facial motoneurons

Authors
Pierson, P.
Published in European Journal of Neuroscience. 2001, vol. 14, no. 6, p. 957-967
Abstract Vasopressin can directly excite facial motoneurons in young rats and mice. It acts by generating a persistent inward current, which is Na(+)-dependent, tetrodotoxin-insensitive and voltage-gated. This peptide-evoked current is unaffected by Ca(++) or K(+) channel blockade and is modulated by extracellular divalent cations. In the present work, we determined how vasopressin alters the input-output properties of facial motoneurons. Whole-cell recordings were obtained from these neurons in the current clamp mode, in brainstem slices of young rats. Repetitive firing was evoked by injecting depolarizing current pulses. Steady-state frequency-current (f-I) relationships were constructed and the effect of vasopressin on these relationships was studied. We found that vasopressin caused a parallel shift to the left of the cell steady-state f-I relationship. This effect persisted in the presence of blockers of K(+) or Ca(++) channels. The peptide effect was distinct from that brought about by Ca(++) channel suppression or by apamin, a blocker of the mAHP. These latter manipulations resulted in an increase in the slope of the steady-state f-I relationship. We conclude that the vasopressin-induced modification of the input-output properties of facial motoneurons is probably exclusively caused by the sodium-dependent, voltage-modulated inward current elicited by the peptide, rather than being due to indirect effects of the peptide on Ca(++) channels, K(+) channels or Ca(++)-dependent K(+) channels. Computer simulation, based on a simple model of facial motoneurons, indicates that the introduction of a conductance having the properties of the vasopressin-dependent conductance can entirely account for the observed peptide-induced shift of the f-I relationship.
Keywords AlgorithmsAnimalsCalcium Channel Blockers/pharmacologyComputer SimulationElectrophysiologyFacial Muscles/drug effects/ innervationMotor Neurons/ drug effectsPatch-Clamp TechniquesPotassium Channel Blockers/pharmacologyRatsRats, Sprague-DawleyVasopressins/ pharmacology
Stable URL http://archive-ouverte.unige.ch/unige:10387
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PMID: 11595034
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