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Lamotrigine and phenytoin, but not amiodarone, impair peripheral chemoreceptor responses to hypoxia

Department of Pediatrics, Yale University School of Medicine, New Haven, Connecticut

Submitted 7 June 2006 ; accepted in final form 4 August 2006

Amiodarone, lamotrigine, and phenytoin, common antiarrhythmic and antiepileptic drugs, inhibit a persistent sodium current in neurons (I_NaP). Previous results from our laboratory suggested that I_NaP is critical for functionality of peripheral chemoreceptors. In this study, we determined the effects of therapeutic levels of amiodarone, lamotrigine, and phenytoin on peripheral chemoreceptor and ventilatory responses to hypoxia. Action potentials (APs) of single chemoreceptor afferents were recorded using suction electrodes advanced into the petrosal ganglion of an in vitro rat peripheral chemoreceptor complex. AP frequency (at PO₂ 150 Torr and PO₂ 90 Torr), conduction time, duration, and amplitude were measured before and during perfusion with therapeutic dosages of the drug or vehicle. Hypoxia-induced catecholamine secretion within the carotid body was measured using amperometry. With the use of whole body plethysmography, respiration was measured in unanesthesized rats while breathing room air, 12% O₂, and 5% CO₂, before and after intraperitoneal administration of amiodarone, lamotrigine, phenytoin, or vehicle. Lamotrigine (10 µM) and phenytoin (5 µM), but not amiodarone (5 µM), decreased chemoreceptor AP frequency without affecting other AP parameters or magnitude of catecholamine secretion. Similarly, lamotrigine (5 mg/kg) and phenytoin (10 mg/kg) blunted the hypoxic but not the hypercapnic ventilatory response. In contrast, amiodarone (2.5 mg/kg) did not alter the ventilatory response to hypoxia or hypercapnia. We conclude that lamotrigine and phenytoin at therapeutic levels impair peripheral chemoreceptor function and ventilatory response to acute hypoxia. These are consistent with I_NaP serving an important function in AP generation and may be clinically important in the care of patients using these drugs.

carotid body; persistent sodium current; anticonvulsants; petrosal neurons

This article has been cited by other articles:

				D. F. Donnelly Spontaneous action potential generation due to persistent sodium channel currents in simulated carotid body afferent fibers J Appl Physiol, May 1, 2008; 104(5): 1394 - 1401. [Abstract] [Full Text] [PDF]