Dopamine penetrates to the central nervous system in developing rats

Background: The purpose of this study was to evaluate whether or not dopami ne (DA) can penetrate to the central nervous system (CNS) from the blood in the infantile period in rats. Methods:ln a preliminary experiment, we administered a 50 mg/kg dose of DA hydrochloride, intraperitoneally, to 7-day-old rats (DA 50 mg/kg group), ob taining cerebrospinal fluid (CSF) both before and at 5, 10, 20, 30, 60 and 120 min after administration. The CSF levels of DA and its main metabolites , 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA), were then measured. Next, we investigated the DA transfer from blood to the CNS by administering doses of 1, 5, 10 and 30 mg/kg DA hydrochloride (DA 1, 5, 10 and 30 mg/kg groups). In these groups, CSF samples were obtained only at 10 and/or 60 min after DA administration, based on the results of the DA 5 0 mg/kg group. Results: The DA concentrations in CSF significantly increased compared with values before DA administration in the DA 50 mg/kg group. The DA concentra tions in the DA 30 mg/kg group, DOPAC concentrations in the DA 5, 10 and 30 mg/kg groups, and HVA concentrations in all groups were significantly high er than in the control (saline injection) group. Conclusions: These findings suggest easy DA transfer from blood to the CNS and immaturity of the blood-blain barrier for DA in the infantile period in rats.