Long-Term Social Isolation Changes the Sensitivity of Monoaminergic Brain Systems to Acute Hypoxia with Hypercapnia

Abstract

The experiments were performed in male albino mice kept in a group or under conditions of long-term social isolation. Changes in the monoaminergic systems of the left and right hemispheres of the brain have been investigated after acute hypoxia with hypercapnia. The levels of dopamine (DA), serotonin (5-HT) and their metabolites, dioxyphenylacetic (DOPAC), homovanillic (HVA), and 5-hydroxyindoleacetic (5‑HIAA) acids, were determined by HPLC in the cerebral cortex, hippocampus, and striatum of the right and left sides of the brain. Control mice kept both in the group and under conditions of social isolation had a higher DA content in the left cerebral cortex. In the other brain structures the monoamine content was symmetric. In the cerebral cortex of mice kept in the group, acute hypoxia with hypercapnia resulted in a right-sided increase in the DA and 5-HT levels. At the same time, the DOPAC content decreased in the left cortex. In mice kept in the group hypoxia with hypercapnia conditions increased the DA level in the left hippocampus. In the striatum, the content of monoamines and their metabolites remained insignificantly changed. In animals kept for a long time under the conditions of social isolation, hypoxia with hypercapnia did not cause any statistically significant changes in the monoamines and their metabolites levels. It has been concluded that the preliminary maintenance under conditions of prolonged social isolation changes the reaction of central monoaminergic systems to acute hypoxia with hypercapnia.