Kinase inhibition lengthens the period of the circadian pacemaker in the eye of Bulla gouldiana.

The inhibition of protein kinase activity by the isoquinoline sulfonamide, H-8, lengthens the period of the Bulla ocular circadian rhythm in a dose-dependent manner. In addition, the phosphorylation of 5 proteins is markedly affected by H-8. The observed correlation between H-8's period lengthening effects, and its effects on the phosphorylation of specific proteins, suggests that: (1) these proteins are candidate components regulating the period of the circadian rhythm; and (2) the daily changes in membrane potential underlying the circadian rhythm are mediated by similar mechanisms that serve to change neural function in other systems; modulation of protein kinases.