An analysis of the involvement of monoaminergic mechanisms in the neuropsychotropic effects of neuroglutam

Abstract

It is known that neuroglutam (at 26 mg/kg) potentiates stereotypy that is induced by the agonist of postsynaptic dopamine receptors apomorphine (1 mg/kg), and suppresses catalepsy that is induced by the blocker of postsynaptic dopamine receptors haloperidol (1 mg/kg), which points to its stimulatory influence on dopaminergic neurotransmission. Neuroglutam (26 mg/kg) does not affect the contents of noradrenaline and dopamine (DA) in homogenates of rat brain structures; however, it increases the concentration of the metabolites of dopamine 3,4-dioxyphenylacetic acid (DOPAC) in the frontal cortex and homovanillic acid (HVA) in the hippocampus, which points to its positive influence on the rate of DA utilization, and, in addition, an increase in indices that characterize the rate of DA turnover, viz., DOPAC/DA and HVA/DA in the striatum. We used the method of radioligand binding in vitro with [G-3H]-sulpiride to show that neuroglutam (10−10–10−4 M) does not directly interact with dopamine D2 receptors; however, during subchronic administration (5 days; a single daily dose of 26 mg/kg) neuroglutam promotes an increase in the density of D2 receptors in the prefrontal cortex, which points to its ability to modulate the expression of these receptors. The data from neurochemical and radioligand analysis suggest that both presynaptic (intensification of metabolic DA turnover) and postsynaptic (DA receptors) mechanisms of dopaminergic neurotransmission are involved in the neuropsychotropic action of neuroglutam. Neuroglutam did not influence the strength of hyperkinesia that was induced by the metabolic precursor of serotonin 5-hydroxytryptophan on the content of serotonin and its metabolites in rat-brain structures and did not alter the receptor binding of [G-3H]-ketanserin (an antagonist of 5-HT2A receptors) in the prefrontal cortex both under in vitro conditions and during subchronic administration ex vivo, which points to the absence of direct participation of the serotonergic system in the pharmacological action of the studied drug.