Effects of unilateral cortical inactivation on monoamine metabolism in symmetrical forebrain areas of white outbred mice

Abstract

Background: In clinical observations and animal experiments, the lateral specificity of the action of compounds that alter monoaminergic transmission has been shown. However, the mechanism of this phenomenon has not yet been studied.
 Aim: To study the effect of unilateral cortical spreading depression on monoamine metabolism in white outbred mice.
 Materials and methods: The experiments were carried out on 18 sexually mature males of white outbred mice. Functional inactivation of the cortex of one of the cerebral hemispheres was caused by unilateral epidural application of 1x1 mm filter paper moistened with 25% KCl solution. 15 minutes after exposure, the animals were decapitated. Using the HPLC method with an electrochemical detector, in the cerebral cortex, hippocampus, olfactory tubercle and striatum the contents of norepinephrine (NE), dopamine (DA), serotonin (5-HT) and their metabolites: dioxyphenylacetic (DOPAC), homovanilinic (HVA) and 5-hydroxyindolacetic (5-HIAA) acids were measured.
 Results. The inactivation of the left hemisphere (ILH) caused a bilateral decrease in the level of NE in the hippocampus, an ipsilateral increase in extracellular metabolism of DA (HVA and/or HVA/DA) in the olfactory tubercle and striatum, as well as a contralateral increase in the content of DA in the cortex and hippocampus. In addition, the ratio of DOPAC/DA in the right olfactory tubercle decreased with ILH. The inactivation of the right hemisphere (IRH) did not cause bilateral effects. With IRH on the inactivation side, the level of NE decreased in the hippocampus, and the level of HVA increased in the striatum. On the opposite (left) side in the IRH mice, the content of DA in the hippocampus increased, as well as the level of DOPAC and the ratio of DOPAC/DA in the olfactory tubercle. Only at IRH, an increase in serotonin metabolism (5-HIAA/5-HT) was detected in the right hippocampus and in the left olfactory tubercle.
 Conclusion. The monoaminergic effects of functional inactivation of the left and right hemisphere cortex in white outbred mice are not mirror-symmetrical.