Halothane and Sevoflurane Exert Different Degrees of Inhibition on Carotid Body Glomus Cell Intracellular Ca²⁺ Response to Hypoxia

Abstract

The purpose of this study was to ascertain if effects of halothane and sevoflurane (0.18–1.45 MAC) on the magnitude of the rise in intracellular calcium ([Ca²⁺]i with ∼90s hypoxia (measured using indo-1 dye) in rat pup carotid body type I glomus cells. paralleled their known effects on the human hypoxic ventilatory response, where halothane is more depressive. We also assessed these agents’ effect on [Ca²⁺]i response to 100 mM K⁺. Halothane depressed the [Ca^2+]i transient in hypoxia more than sevoflurane (p = 0.036). Both agents also depressed the [Ca²⁺]i response to K+ – halothane more than sevoflurane (p = 0.004). These actions reflect their known influence on human hypoxic ventilatory response, consistent with the notion that the cellular process underlies the whole-body effect. The responses to K⁺, which depolarises the cell membrane, indicates that in addition to a putative effect on K⁺ channels, voltage-activated Ca²⁺ channels may also be involved in the anaesthetic effect.