DARK PHASE-INDUCED LOCOMOTOR-ACTIVITY ASSOCIATED WITH THE PLASMA-LEVEL OF BETA-PHENYLETHYLAMINE IN RAT

The correlations between locomotor activity and the plasma level of be ta-phenylethylamine (PEA) and dopaminergic indices in discrete regions of rat brain were investigated. Rats were placed in photocell cages a nd their locomotor activity was recorded continuously for 62 hours. A light/ dark cycle (12 hrs/ 12 hrs) was maintained in the cages. Rats w ere then sacrificed, the brains were removed and the plasma was collec ted. The levels of dopamine, 3,4-dihydroxyphenylacetic acid (DOPAC) an d homovanillic acid in the discrete brain regions were measured by hig h performance liquid chromatography. The plasma level of PEA was measu red by gas chromatography-mass spectrometry. The exploratory activitie s during the first hour after the rats were replaced in the photocell cage was positively correlated with the DOPAC level of the prefrontal cortex (r=0.47,P=0.035). The plasma level of PEA was positively correl ated with the activity measured during the first hour of the dark phas e (r=0.60, P=0.0053). These data indicate that the plasma level of PEA reflects the individual general activity but not the locomotor respon se to novelty, which correlated with the dopaminergic activity in the prefrontal cortex.