Involvement of brain dopaminergic systems in the development of an MPTP-induced depressive state in rats.

A depressive state was induced in Wistar rats by repeated i.p. injections of the proneurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), which induces the death of dopaminergic neurons in the brain. Signs of the development of the experimental depressive state were a reduction in body weight and an increase in the proportion of REM sleep during daytime sleep. The rearrangement of the spectral characteristics of electrical activity during the development of experimental depressive syndrome in rats was shown to occur in target structures of the nigrostriatal, mesocortical, and mesolimbic dopaminergic systems of the brain, as well as in the amygdala and hippocampus. The most marked changes were seen in the terminal field of the nigrostriatal dopaminergic system and hippocampus. Spectral rearrangements of electrical activity in the theta-1 and theta-2 ranges in the hippocampus and dopaminergic structures suggest the involvement of the hippocampus in mediating changes in the emotional status of the experimental animals during the development of the MPTP-induced depressive state.