Two types of increases in free Ca²⁺ evoked by odor in isolated frog olfactory receptor neurons

Abstract

OLFACTORY transduction involves second messenger-related enzymes and cAMP-gated, K⁺ and Ca²⁺ channels, which are known to be regulated by Ca²⁺. We report here that cytosolic free Ca²⁺ concentration ([Ca²⁺].) in olfactory receptor neuron was increased by odorants or forskolin and Ca²⁺ influx contributed to the adaptation. The increases in [Ca²⁺]; were below two to three-fold of resting level and transient for 26 s (mean value, n=18). The increases were due to two pathways: Ca²⁺ influx and release. The slow increases in [Ca²⁺], by forskolin resembled those by citralva. It was suggested that the responses to citralva were accompanied by increases in intracellular cAMP and Ca²⁺ influx or release leading to transient increases in [Ca²⁺].