Hippocampal asymmetry in expression of catecholamine synthesizing enzyme and transporters in socially isolated rats

Abstract

OBJECTIVES: Right-left asymmetry of human brain function has been known for a century. Brain asymmetry and lateralization has been observed at the neurochemical level. At the neurochemical level, it is important to further correlate changes in monoaminergic activity with the synthesis and reuptake of these monoamines. The aim of the present study was to analyze the effect of social isolation on catecholamine stores as well as on the regulation of catecholamine synthesis and uptake in the right and left hippocampus. METHODS: We examined changes in protein levels of dopamine-beta-hydroxylase (DBH), norepinephrine transporter (NET) and vesicular monoamine transporter 2 (VMAT2) in the right and left hippocampus of socially isolated adult male rats during 12 weeks by Western blot analysis. RESULTS: Chronic isolation stress reduced norepinephrine content in the right hippocampus. No changes were observed in protein levels of DBH and NET in the right hippocampus, whereas expression of this norepinephrine synthetizing enzyme and transporter were elevated in the left hippocampus. On the other hand, chronic isolation stress caused reduction of VMAT2 protein in the right hippocampus. CONCLUSION: Our results reveale not only the lateralization of stress regulatory system but they also show that long-term isolation stress produces right-left asymmetry of the hippocampus norepinephrine, different regulation of the catecholamines synthesis and reuptake.