The behavioral pharmacological effects of Ca-4-(3,5-dihydroxy-3-methylpenthylamido) butyrate (mevalonic-GABA, MV-GABA), a new GABA derivative were studied in comparison with those of Ca-hopantenate (HOPA) in mice. MV-GABA had no effect on the general behavior and electric shock-induced fighting behavior. The dosage of MV-GABA which caused locomotor hypoactivity produced an impairment of the rotarod performance. MV-GABA inhibited the hyperactivity induced by a dopamine (DA) agonist (methamphetamine) and acetylcholine (ACh) antagonists (scopolamine and atropine) at a dose which did not affect locomotor activity in normal mice. MV-GABA prolonged the pentobarbital-Na-induced sleeping time, and it prolonged the latencies until convulsion and death after administration of strychnine. MV-GABA and HOPA antagonized the electroconvulsive shock-induced amnesia in the passive avoidance response of mice. These results suggest that MV-GABA has effects on the central nervous systems, in particular, ACh and DA neural systems. The actions of MV-GABA were qualitatively similar to those of HOPA except for the effect on the DA neural system.