Effects of trifluoperazine and amiloride on the extrusion of axoplasmic Ca++ by rapidly adapting and slowly adapting type I cutaneous mechanoreceptors: an electron-microscopic study using the oxalate-antimonate method.
Influences of Ca++ transport inhibitors on the extrusion of cytosolic Ca++ from axon terminals of oral mucosal mechanoreceptors were cytochemically studied through the use of trifluoperazine (TFP), a Ca++ pump inhibitor, and amiloride, a Na+/Ca++ exchanger inhibitor. Palates of Mongolian gerbils were isolated after perfusion with normal, TFP-containing, or amiloride-containing HEPES-buffered saline, and then mechanically stimulated in the same buffer. Cytosolic Ca++ in axon terminals at 2 min after the stimulation was visualized by means of an oxalate-antimonate method using microwave fixation, and then evaluated electron-microscopically. TFP was found to inhibit the Ca++ extrusion from axon terminals of Meissner corpuscles, but not from those of Merkel cell-axon complexes. Conversely, amiloride severely reduced the Ca++ extrusion from axon terminals of Merkel cell-axon complexes, but not from those of Meissner corpuscles. These results suggest that cytosolic Ca++ extrusion from axon terminals of rapidly adapting and slowly adapting type I mechanoreceptors is regulated by a Ca++ pump and an Na+/Ca++ exchanger, respectively.
Department of Oral Anatomy, Iwate Medical University School of Dentistry, Morioka, Japan.
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D000584:Amiloride / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000187:drug effects*; D003600:Cytosol / Q000187:drug effects; D005260:Female; D005849:Gerbillinae; D008297:Male; D008465:Mechanoreceptors / Q000187:drug effects*; D008854:Microscopy, Electron; D017729:Presynaptic Terminals / Q000187:drug effects*; D012867:Skin / Q000294:innervation*; D009435:Synaptic Transmission / Q000187:drug effects; D014268:Trifluoperazine / Q000494:pharmacology*
D015220:Calcium Channels; D014268:Trifluoperazine; D000584:Amiloride; D002118:Calcium