Specific actions of cyanide on membrane potential and voltage-gated ion currents in rostral ventrolateral medulla neurons in rat brainstem

The present study examined specific effects of sodium cyanide (CN) on the m embrane potential (MP), spontaneous discharge (SID) and voltage-gated ion c urrent of the identified bulbospinal rostral ventrolateral medulla (RVLM) n euron in the rat pup brainstem slice. 125 muM CN rapidly depolarized MP in the RVLM neuron by 11.6 mV as well as enhanced the SID rate by 300%. In con trast, the same dose of CN immediately hyperpolarized unlabeled, non-RVLM n eurons by 4.8 mV. 50 muM CN did not significantly affect voltage-gated Ca+ or A-type K+ currents. The same concentration of CN, however, rapidly and reversibly suppressed voltage-gated Na+ currents and sustained outward K+ c urrents in the RVLM neuron by 22.5% and 23%, respectively. Tetraethylammoni um could mimic the effect of CN on MP, SID and sustained K+ current in the RVLM neuron. It is concluded that: (1) like that from the adult rat, the ra t pup bulbospinal RVLM neuron can be selectively and rapidly excited by CN; (2) the hypoxia-sensitive, sustained outward K+ channel may play an import ant role in the acute hypoxia-induced excitation of the RVLM neurons. (C) 2 001 Elsevier Science Ireland Ltd. All rights reserved.