Behavioral lateralization in the T-maze and monoaminergic brain asymmetries.

Recently we have reported a marked rat lateralization in the T-maze choice. The present study examines the relationship between the ascending monoaminergic systems and the T-maze behavioral asymmetry. There were no significant differences for serotonin or norepinephrine between the T-maze preferred and non-preferred brain sides in the s. nigra, ventral tegmental area, striatum, acumbens, frontal lobe or hippocampus. Only in the hippocampus was dopamine concentration significantly greater for the brain site ipsilateral to the T-maze choice side. Previously, we reported that both apomorphine, a dopamine receptor agonist, and 6-hydroxydopamine lesion in the medial forebrain bundle of the catecholaminergic neurons affect the T-maze asymmetry; we therefore suggested that the T-maze choice could be related with the ascending dopaminergic systems. The present data strongly support this hypothesis and suggest that the DA cells involved in the spatial asymmetry in the T-maze are included in the dopaminergic mesohippocampal system.