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

Abstract

BACKGROUND: Clinical observations and animal experiments have shown the lateral specificity of the action of compounds that alter monoaminergic transmission. However, the mechanism of this phenomenon has not yet been studied. AIM: To evaluate the effect of unilateral cortical spreading depression on monoamine metabolism in white outbred mice. MATERIALS AND METHODS: Eighteen sexually mature male white outbred mice were studied. Functional inactivation of the cortex of one of the cerebral hemispheres was induced using unilateral epidural application of 1 × 1 mm filter paper moistened with 25% KCl solution. Then, 15 minutes after exposure, the animals were decapitated. The norepinephrine, dopamine, serotonin, and metabolite (i.e., dioxyphenylacetic (DOPAC), homovanilinic (HVA), and 5-hydroxyindolacetic (5-HIAA) acids) content of the cerebral cortex, hippocampus, olfactory tubercle, and striatum was measured using the HPLC method with an electrochemical detector. RESULTS: The inactivation of the left hemisphere was due to a bilateral decrease in norepinephrine in the hippocampus, an ipsilateral increase in extracellular metabolism of dopamine (HVA and/or HVA/dopamine) in the olfactory tubercle and striatum, and a contralateral increase of dopamine in the cortex and hippocampus. Furthermore, the DOPAC/dopamine ratio in the right olfactory tubercle decreased with left hemisphere inactivation. Right hemisphere inactivation did not cause bilateral effects. With inactivation of the right hemisphere on the inactivation side, norepinephrine in the hippocampus decreased and HVA in the striatum increased. In the left side, with the inactivation of the right hemisphere mice, dopamine in the hippocampus increased, as well as the DOPAC level and DOPAC/dopamine ratio in the olfactory tubercle. Serotonin metabolism (5-HIAA/serotonin) in the right hippocampus and left olfactory tubercle increased only at inactivation of the right hemisphere. CONCLUSIONS: The monoaminergic effects of functional inactivation of the left and right hemisphere cortex in white outbred mice are not mirror-symmetrical.

Keywords

cortical spreading depression / monoamines / brain asymmetry

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