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Neuropharmacology. 2016 Sep;108:120-7. doi: 10.1016/j.neuropharm.2016.04.034. Epub 2016 Apr 27.

Activation of D2 autoreceptors alters cocaine-induced locomotion and slows down local field oscillations in the rat ventral tegmental area.

Author information

1
Laboratory of Pharmacology, Department of Biomedical and Preclinical Sciences, and Laboratory of Neurophysiology, GIGA Neurosciences, University of Liège, B-4000 Liège, Belgium.
2
Department of Electrical Engineering and Computer Science, University of Liège, B-4000 Liège, Belgium.
3
Department of Behavioral and Cognitive Psychology, University of Liège, B-4000 Liège, Belgium.
4
Institute for Automation Engineering, Department for Systems Theory and Automatic Control, Otto-von-Guericke University Magdeburg, Germany.
5
Laboratory of Pharmacology, Department of Biomedical and Preclinical Sciences, and Laboratory of Neurophysiology, GIGA Neurosciences, University of Liège, B-4000 Liège, Belgium. Electronic address: V.Seutin@ulg.ac.be.

Abstract

Psychoactive substances affecting the dopaminergic system induce locomotor activation and, in high doses, stereotypies. Network mechanisms underlying the shift from an active goal-directed behavior to a "seemingly purposeless" stereotypic locomotion remain unclear. In the present study we sought to determine the relationships between the behavioral effects of dopaminergic drugs and their effects on local field potentials (LFPs), which were telemetrically recorded within the ventral tegmental area (VTA) of freely moving rats. We used the D2/D3 agonist quinpirole in a low, autoreceptor-selective (0.1 mg/kg, i.p.) and in a high (0.5 mg/kg, i.p.) dose, and a moderate dose of cocaine (10 mg/kg, i.p.). In the control group, power spectrum analysis revealed a prominent peak of LFP power in the theta frequency range during active exploration. Cocaine alone stimulated locomotion, but had no significant effect on the peak of the LFP power. In contrast, co-administration of low dose quinpirole with cocaine markedly altered the pattern of locomotion, from goal-directed exploratory behavior to recurrent motion resembling locomotor stereotypy. This behavioral effect was accompanied by a shift of the dominant theta power toward a significantly lower (by ∼15%) frequency. High dose quinpirole also provoked an increased locomotor activity with signs of behavioral stereotypies, and also induced a shift of the dominant oscillation frequency toward the lower range. These results demonstrate a correlation between the LFP oscillation frequency within the VTA and a qualitative aspect of locomotor behavior, perhaps due to a variable level of coherence of this region with its input or output areas.

KEYWORDS:

Cocaine; Local field potential; Quinpirole; Stereotypies; Ventral tegmental area

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