POSSIBLE MEDIATION OF G-PROTEINS IN COLD-SENSORY TRANSDUCTION IN PARAMECIUM-MULTIMICRONUCLEATUM

The possible involvement of G-proteins in cold-sensory transduction wa s examined using voltage-clamped Paramecium multimicronucleatum into w hich nonhydrolyzable guanosine nucleotide analogues had been applied i ntracellularly. Guanosine-5'-O-3-thiotriphosphate, guanosine-5'-O-2-th iodiphosphate and aluminium fluoride all reduced the transient inward current in response to cooling, suggesting the possibility that G-prot eins mediate cold-sensory transduction. Internal application of a Ca2 chelator, EGTA, also reduced the current response. In addition to the ir effect on reducing the cold-sensory response, application of these chemicals modulated both the resting potential and the membrane conduc tance. Possible correlations between G-protein activity and the regula tion of intracellular Ca2+ levels are discussed.