Involvement of CaMKIV in neurogenic effect with chronic fluoxetine treatment.

Calcium-calmodulin dependent protein kinase IV (CaMKIV) is a protein kinase that has been suggested to participate in fluoxetine (FLX)-induced phosphorylation of cyclic AMP-response element binding protein (CREB). CREB is a key transcription factor in adult neurogenesis. The present study aimed at evaluating whether CaMKIV is involved in adult hippocampal neurogenesis with FLX treatment. Effects of chronic FLX on hippocampal cell proliferation, survival and phenotypes were assessed using bromodeoxyuridine (BrdU) immunohistochemistry or BrdU/neuronal nuclei (NeuN)/S100β immunofluorescence staining in wild-type (WT) and CaMKIV knockout (KO) mice. Expression and phosphorylation of CaMKIV and CREB were assessed using RT-PCR and Western blotting. The behavioural action with FLX was assessed in the novelty suppressed feeding test (NSF), which is considered neurogenesis-dependent. CaMKIV KO mice have reduced cell proliferation, but not survival in the dentate gyrus of hippocampus with chronic treatment of FLX when compared to wild littermates. Phenotype analysis showed that most newborn cells matured into neurons. Phosphorylation of CaMKIV was up-regulated in WT mice and phosphorylation of CREB was impaired in CaMKIV KO mice after FLX treatment. The behavioural effects of FLX in NSF were similar in both types. These data suggest that CaMKIV is involved in some aspects of FLX-promoting hippocampal neurogenesis.