Acetylcholine modulation of the conductance of intercellular junctions between rat lacrimal cells.

Abstract

The conductance of intercellular junctions between rat lacrimal cells was studied with the double whole‐cell tight‐seal recording technique. This conductance decreases spontaneously with time as a result of the double‐cell dialysis. The rate of this 'spontaneous' uncoupling is unaffected by changing the internal Ca concentration, [Ca]i, between 10(‐8) M and 10(‐6) M. This rate of uncoupling is greatly increased when [Ca]i is approximately 10(‐5) M, and this effect does not involve changes in the internal proton concentration. When [Ca]i is weakly buffered in one of the two cells, 1‐2 microM‐acetylcholine (ACh) both activates Ca‐dependent channels in that cell (Marty, Tan & Trautmann, 1984) and uncouples the two cells. The uncoupling is not synchronous with the increase in [Ca]i as reflected by the Ca‐dependent currents. When [Ca]i is strongly buffered in both cells, ACh fails to activate Ca‐dependent currents, but it can still uncouple the cells. This ACh‐induced uncoupling is often preceded by a transient enhancing of the coupling. In conclusion, ACh has several distinct effects on lacrimal cells: activation of Ca‐dependent channels in the plasma membrane, closure of junctional channels involving a Ca‐independent mechanism, and sometimes, an increase in the junctional coupling by a Ca‐independent mechanism. © 1986 The Physiological Society