Haloperidol-Induced Hypokinesia in Rats is Differentially Affected by the Light/Dark Phase, Age, and Melatonin.

Haloperidol-Induced Hypokinesia in Rats is Differentially Affected by the Light/Dark Phase, Age, and Melatonin.
Behav Brain Res. 2019 Nov 09;:112313
Authors: Hussain S, Villarreal S, Ramirez N, Hussain A, Sumaya IC
Abstract
It has been well established that the striatal dopaminergic system is compromised with aging, namely D2 receptor function. Also well documented is the age related decline of the neurohormone, melatonin, in both humans and nonhuman animals. What has not been well studied is the possible interaction between the D2 receptor system and the age related decline in melatonin with its unmistakable pattern of synthesis and release exclusively during the dark phase. We tested the effect of the D2 antagonist, haloperidol (1.0 mg/kg ip), in adolescent (2 mo old) and adult rats (10 mo old) in the light (ZT3) and dark phases (ZT 15) in rats kept in a 12 L/12D cycle and the effect of exogenous melatonin (15 mg/kg ip/day x 4 days for a total of 60 mg/kg) on D2 antagonism. Using the bar test, measuring the extrapyramidal side-effect of hypokinesia, we report haloperidol to work differentially depending on both age and phase. Adult rats experienced the effect of the D2 antagonist in both the light and dark phases, while younger rats did not show hypokinetic affects in the dark. By manipulated lighting, we were able to restore the effect of haloperidol in younger rats in the dark phase. We also found ameliorating effects of ...

Source: Behavioural Brain Research - November 8, 2019 Category: Neurology Authors: Hussain S, Villarreal S, Ramirez N, Hussain A, Sumaya IC Tags: Behav Brain Res Source Type: research