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Unilateral mesolimbicocortical dopamine denervation decreases locomotion in the open field and after amphetamine
Abstract:
Unilateral denervation of the mesolimbicocortical dopaminergic (DA) system was produced by microinjections of 6-hydroxydopamine (6-OHDA) into the right or left anterolateral hypothalamus after desmethylimipramine pretreatment. Unilateral DA denervation was confirmed by the marked loss of fluorescent fibers in mesolimbic DA terminal fields in brains processed for catecholamine histofluorescence with the glyoxylic acid-paraformaldehyde method. Such unilateral DA denervation significantly decreased the locomotor exploration of an open field and the locomotor response to d-amphetamine (1.5 mg/kg). These results demonstrate that unilateral mesolimbococortical DA denervation is sufficient, and that bilateral denervation of a single amphetamine or a decrease of locomotion in the open field. The results are consistent with the hypothesis that the mesolimbicocortical DA system energizes behavior, but does not direct it.
Insights
Unilateral denervation of the brain's dopamine system reduced exploratory behavior and amphetamine response. This suggests the dopamine system energizes actions but doesn't dictate specific movements.
Area of Science:
- Neuroscience
- Behavioral Neuroscience
- Neuropharmacology
Background:
- The mesolimbicocortical dopaminergic (DA) system plays a crucial role in motivated behaviors.
- Understanding the specific functions of this DA system requires precise experimental manipulation.
Purpose of the Study:
- To investigate the effects of unilateral denervation of the mesolimbicocortical DA system on locomotor activity and amphetamine-induced responses.
- To determine if unilateral DA denervation is sufficient to alter behavior.
Main Methods:
- Unilateral denervation of the DA system was achieved using 6-hydroxydopamine (6-OHDA) microinjections into the anterolateral hypothalamus.
- Desmethylimipramine pretreatment protected DA neurons from 6-OHDA toxicity.
- Catecholamine histofluorescence confirmed successful DA denervation.
Main Results:
- Unilateral DA denervation significantly decreased locomotor exploration in an open field.
- The locomotor response to d-amphetamine was significantly reduced following unilateral DA denervation.
- These findings indicate that even partial denervation impacts motor activity.
Conclusions:
- Unilateral denervation of the mesolimbicocortical DA system is sufficient to impair locomotor exploration and amphetamine response.
- The mesolimbicocortical DA system appears to energize behavior rather than direct specific actions.
- These results support the hypothesis that DA system activity is critical for behavioral activation.