Cardiorespiratory neurons of the rat ventrolateral medulla contain TASK-1 and TASK-3 channel mRNA.

The potassium channels TASK-1 and TASK-3 are neuronal 'leak' channels that are inhibited by extracellular acidification and numerous neurotransmitters. Here we tested whether in the rat TASK-1 and TASK-3 mRNAs are present in ventrolateral medulla neurons that regulate respiration or circulation (C1 adrenergic neurons). The mRNAs were identified by in situ hybridization. Respiratory neurons were identified by anatomical markers (neurokinin-1 receptors, NK1R, or somatostatin) or directly by juxtacellular labeling of bulbospinal neurons. C1 neurons were identified by the presence of tyrosine-hydroxylase. TASK-1 and TASK-3 transcripts were present in all hypoglossal and facial motor neurons, in most C1 cells (85-95%), in most small and large NK1R-ir neurons (>90%) of the ventral respiratory group (VRG) and in all the inspiratory-augmenting bulbospinal neurons of the rostral ventral respiratory group. In conclusion, TASK channels are expressed by respiratory cells with putative rhythmogenic function and by premotor and motor neurons. TASK channels presumably mediate excitatory effects of numerous transmitters on these neurons and may contribute to their pH-sensitivity.