Dopamine penetrates to the central nervous system in developing rats.

Abstract

The purpose of this study was to evaluate whether or not dopamine (DA) can penetrate to the central nervous system (CNS) from the blood in the infantile period in rats. In a preliminary experiment, we administered a 50 mg/kg dose of DA hydrochloride, intraperitoneally, to 7-day-old rats (DA 50 mg/kg group), obtaining 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 50 mg/kg group. The DA concentrations in CSF significantly increased compared with values before DA administration in the DA 50 mg/kg group. The DA concentrations 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 higher than in the control (saline injection) group. These findings suggest easy DA transfer from blood to the CNS and immaturity of the blood-brain barrier for DA in the infantile period in rats.