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Locomotor activity initiated by microinfusions of picrotoxin into the ventral tegmental area
Abstract:
Ambulatory activity in rats was increased in a dose-related manner by microinjections of picrotoxin, a GABA antagonist, bilaterally into the ventral tegmental area. Microinjections of strychnine, a glycine antagonist, had no effect on activity. The ambulatory activity induced by microinjections of picrotoxin into the ventral tegmental area was significantly attenuated when the nucleus accumbens was pretreated with spiroperidol, a dopamine antagonist. These findings provide additional evidence that dopaminergic (A10) neurons projecting from the ventral tegmental area to the nucleus accumbens, contribute to locomotor activity. It is suggested that picrotoxin disinhibits the A10 dopaminergic neurons projecting to the nucleus accumbens.
Insights
Microinjections of picrotoxin into the ventral tegmental area increased rat ambulatory activity. This effect was blocked by dopamine antagonists, suggesting GABAergic inhibition of dopamine neurons contributes to locomotor control.
Area of Science:
- Neuroscience
- Behavioral Pharmacology
Background:
- The ventral tegmental area (VTA) is implicated in reward and motivation.
- Dopaminergic neurons in the VTA project to the nucleus accumbens and influence motor activity.
Purpose of the Study:
- To investigate the role of GABAergic and glycinergic neurotransmission in the VTA on locomotor activity.
- To determine the involvement of dopamine in picrotoxin-induced locomotion.
Main Methods:
- Rats received bilateral microinjections of picrotoxin (GABA antagonist) or strychnine (glycine antagonist) into the VTA.
- Locomotor activity was measured.
- The nucleus accumbens was pretreated with spiroperidol (dopamine antagonist) before VTA picrotoxin injections.
Main Results:
- Picrotoxin dose-dependently increased ambulatory activity.
- Strychnine had no effect on activity.
- Spiroperidol pretreatment significantly reduced picrotoxin-induced locomotion.
Conclusions:
- GABAergic, but not glycinergic, inhibition in the VTA modulates locomotor activity.
- Dopaminergic neurons projecting from the VTA to the nucleus accumbens are critical for this motor behavior.
- Picrotoxin likely disinhibits these A10 dopaminergic neurons, leading to increased activity.