Distinct Effects of Nonselective Rho‐Kinase Inhibitor Fasudil and Selective Rho‐Kinase 2 Inhibitor <scp>KD025</scp> on Serotonin and Dopamine Release in the Nucleus Accumbens of Mice

ABSTRACT Recent studies have indicated that the Rho GTPase family and Rho‐kinases are associated with psychiatric diseases, such as schizophrenia. Two subtypes of Rho‐kinase, Rho‐kinases 1 and 2, regulate actin dynamics and mediate neurite outgrowth, spine morphology in neurons, and neurotransmitter release in vitro and ex vivo. However, the precise role of Rho‐kinases in neurotransmitter release in vivo remains unclear. To clarify the role of Rho‐kinases 1 and 2 in serotonin and dopamine release in the nucleus accumbens (NAc) of mice in vivo, we investigated the effect of a nonselective Rho‐kinase inhibitor, fasudil, and a selective Rho‐kinase 2 inhibitor, KD025, using an in vivo microdialysis technique. Fasudil perfusion (1–20 μM) into the NAc increased the basal extracellular serotonin level but did not affect dopamine levels, whereas KD025 (10–20 μM) had little effect on basal serotonin and dopamine levels. Notably, fasudil perfusion into the NAc suppressed depolarization‐induced serotonin and dopamine release in a dose‐dependent manner, whereas KD025 selectively suppressed depolarization‐induced serotonin release. Our results suggested that Rho‐kinases 1 and 2 are associated with dopamine and serotonin release, respectively, and that both may have significant but distinct roles in the regulation of serotonin and dopamine release in the NAc.