EFFECTS OF TRIFLUOPERAZINE AND AMILORIDE ON THE EXTRUSION OF AXOPLASMIC CA-I CUTANEOUS MECHANORECEPTORS - AN ELECTRON-MICROSCOPIC STUDY USING THE OXALATE ANTIMONATE METHOD(+ BY RAPIDLY ADAPTING AND SLOWLY ADAPTING TYPE)

Influences of Ca++ transport inhibitors on the extrusion of cytosolic Ca++ from axon terminals of oral mucosal mechanoreceptors were cytoche mically studied through the use of trifluoperazine (TFP), a Ca++ pump inhibitor, and amiloride, a Na+/Ca++ exchanger inhibitor. Palates of M ongolian gerbils were isolated after perfusion with normal, TFP-contai ning, or amiloride-containing HEPES-buffered saline, and then mechanic ally stimulated in the same buffer. Cytosolic Ca++ in axon terminals a t 2 min after the stimulation was visualized by means of an oxalate-an timonate 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-a xon complexes. Conversely, amiloride severely reduced the Ca++ extrusi on from axon terminals of Merkel cell-axon complexes, but not from tho se of Meissner corpuscles. These results suggest that cytosolic Ca++ e xtrusion from axon terminals of rapidly adapting and slowly adapting t ype I mechanoreceptors is regulated by a Ca++ pump and an Na+/Ca++ exc hanger, respectively.