Depolarization-induced effects of Ca2+-calmodulin-dependent protein kinase injection, in vivo, in single neurons of cat motor cortex.

Intracellular injection of calcium-calmodulin-dependent protein kinase followed by depolarization and depolarization-elicited impulse activity increased input resistance of neurons of the motor cortex of cats. Protein kinase alone or depolarization in the absence of protein kinase did not produce this effect. An analogous increase of input resistance can be produced in the type B photoreceptor of Hermissenda by applying protein kinase and sufficient depolarization to increase calcium conductance and internal Ca2+ concentration. Given previous studies linking changes in both types of neurons to the development of conditioning, the results suggest the possibility of shared biochemical steps in mechanisms of neuronal adaptation by vertebrate and invertebrate species.