Inactivation of cGKI in the CNS causes adaptation defects in the circadian clock in mice

The cGK family of cGMP-dependent protein kinases, also known as PKG, has been described to be involved in the regulation of a broad variety of physiological processes. More recently, cGKI and II have been implicated in the resetting of the master circadian clock located in the suprachiasmatic nuclei (SCN). Notably, cgkII knockout mice show reduced phase delays and reduced Per2 induction in the early subjective night. These results are in contrast to studies using pharmacological cGK inhibitors. Since in mice, both cGKs are expressed in the SCN, we set out to investigate the wheel running behavior of cgkI knockout mice to study the possible involvement of cGKI in resetting the circadian clock in mice.