Temperature dependence of muscarinic acetylcholine receptor activation, desensitization, and resensitization

The effects of temperature on muscarinic acetylcholine receptor activation, densitization, and resensitization were studied with the use of intact mouse neuroblastoma cells (clone N1E-115), which have muscarinic receptors that mediate cyclic GMP synthesis. Below 15-20°C, activation or desensitization of muscarinic receptors by carbamylcholine and recovery from desensitization (caused by carbamylcholine at 37°C) did not occur. Above these temperatures, the apparent rates of receptor-mediated cyclic GMP synthesis, desensitization, and recovery of sensitivity increased at the incubation temperature was increased. Arrhenius plots of the data yielded activation energies of 25, 14, and 23 kcal.mol^-1 for activation, desensitization, and resensitization, respectively. These data suggest that a certain degree of membrane phospholipid fluidity is required for these processes to occur.