Chlorimipramine, electroconvulsive shock and combination thereof: Differential effects of chronic treatment on apomorphine-induced behaviours and on striatal and mesocortical dopamine turnover

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Abstract
We studied the influence of different pretreatment regimens (Chlorimipramine-Cmi, electroconvulsive shock-ECS, and Cmi+ECS all regimens being applied for either 2 or 15 days) on the open field behaviour, on the striatal and on the prefrontal dopamine-PFC DA turnover in rats injected with either apomorphine-AP 25 μg/kg (stimulating presynaptic DA receptors), AP 200 μg/kg (stimulating postsynaptic DA receptors), or vehicle (control). In the controls, AP 25 μg/kg reduced the locomotor activity and the striatal, but not the PFC DA turnover. AP 200 μg/kg increased the locomotor activity and reduced the striatal but not the PFC DA turnover. Short-term pretreatment: ECS and Cmi+ECS prevented the decrease of striatal DA turnover after AP 25 μg/kg. No other influence of any pretreatment on behaviour or DA-turnover became significant. Long-term pretreatment: Chronic Cmi: marginally increased the open field behaviour and marginally decreased the PFC DA turnover; significantly increased the effect of AP (200 μg/kg) on striatal DA turnover and the effect of AP (25 and 200 μg/kg) on PFC DA turnover. Repeated ECS: decreased locomotion and rearing and increased PFC DA turnover; increased the effect of AP (200 μg/kg) on locomotion and on striatal DA turnover; decreased the effect of AP (25 and 200 μg/kg) on PFC DA turnover. Chronic Cmi+ECS: decreased locomotion and rearing and marginally decreased PFC DA turnover; increased the effect of AP on hyperlocomotion and on striatal DA turnover. No other influence of any chronic pretreatment on behaviour or on DA turnover became significant. The data support the view that chronic AD therapies increase DAergic functions related to postsynaptic rather than to presynaptic structures. It is suggested that the different effects of chronic Cmi and repeated ECS on AP-evoked PFC DA turnover help to understand the different influences exerted by both treatments on rats' behaviour.