Ketamine reversed short-term memory impairment and depressive-like behavior in animal model of Parkinson's disease.

Ketamine reversed depressive-like behaviors and short-term memory impairment in rats with Parkinson's disease-like brain lesions. Male rats received a toxin injection into the substantia nigra pars compacta, which caused short-term social memory loss, reduced sucrose preference (anhedonia), and increased immobility in a forced swim test. Ketamine at 5, 10, and 15 mg/kg once weekly reversed all these effects, with the anti-immobility effect linked to increased swimming, suggesting a serotonergic mechanism. Imipramine also reduced immobility. Neither ketamine nor imipramine restored the dopamine-producing cells lost to the toxin. The results suggest ketamine may help treat depression and memory problems in Parkinson's disease.

Study at a glance

Abstract

The most common features of Parkinson's disease (PD) are motor impairments, but many patients also present depression and memory impairment. Ketamine, an N-methyl-d-aspartate (NMDA) receptor antagonist, has been shown to be effective in patients with treatment-resistant major depression. Thus, the present study evaluated the action of ketamine on memory impairment and depressive-like behavior in an animal model of PD. Male Wistar rats received a bilateral infusion of 6 μg/side 6-hydroxydopamine (6-OHDA) into the substantia nigra pars compacta (SNc). Short-term memory was evaluated by the social recognition test, and depressive-like behaviors were evaluated by the sucrose preference and forced swimming tests (FST). Drug treatments included vehicle (i.p., once a week); ketamine (5, 10 and 15 mg/kg, i.p., once a week); and imipramine (20 mg/kg, i.p., daily). The treatments were administered 21 days after the SNc lesion and lasted for 28 days. The SNc lesion impaired short-term social memory, and all ketamine doses reversed the memory impairment and anhedonia (reduction of sucrose preference) induced by 6-OHDA. In the FST, 6-OHDA increased immobility, and all doses of ketamine and imipramine reversed this effect. The anti-immobility effect of ketamine was associated with an increase in swimming but not in climbing, suggesting a serotonergic effect. Ketamine and imipramine did not reverse the 6-OHDA-induced reduction in tyrosine hydroxylase immunohistochemistry in the SNc. In conclusion, ketamine reversed depressive-like behaviors and short-term memory impairment in rats with SNc bilateral lesions, indicating a promising profile for its use in PD patients.