Acetylcholine modulation of the conductance of intercellular junctions between rat lacrimal cells.
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.
D000109:Acetylcholine / Q000494:pharmacology*; D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D002118:Calcium / Q000494:pharmacology / Q000502:physiology; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D007365:Intercellular Junctions / Q000502:physiology*; D007473:Ion Channels / Q000187:drug effects*; D007765:Lacrimal Apparatus / Q000502:physiology*; D051381:Rats; D013997:Time Factors
D007473:Ion Channels; D000109:Acetylcholine; D002118:Calcium