T-type calcium channels: heterogeneous expression in rat sensory neurons and selective modulation by phorbol esters.
We report selective inhibition of low-threshold, T-type calcium channels by a phorbol ester in rat sensory neurons. Cells were exposed, either acutely or with 15-60 min preincubations, to low concentrations of phorbol 12-myristate 13-acetate, (PMA), an activator of protein kinase C; if the temperature was 29 degrees C or higher, T-type Ca current was diminished without effect on high-threshold Ca current. In untreated cells, the amplitude of T-type Ca current varies widely among neighboring sensory neurons. T channels are absent in about 25% of cells, provide a small current near threshold for the majority of cells, and are a dominant pathway for calcium entry in a small subset of neurons. The results are of interest because, by selectively inhibiting a calcium channel expressed differently among subpopulations of sensory neurons, activation of protein kinase C might selectively suppress particular sensations.
Schroeder
J E
JE
Department of Cell Biology and Physiology, Washington University, St. Louis, Missouri 63110.
Fischbach
P S
PS
McCleskey
E W
EW
D000818:Animals; D002121:Calcium Channel Blockers / Q000378:metabolism; D015220:Calcium Channels / Q000378:metabolism*; D004056:Differential Threshold; D009475:Neurons, Afferent / Q000378:metabolism*; D051381:Rats; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D013755:Tetradecanoylphorbol Acetate