Changed state – changed brain: shift of the dominant frequency of theta oscillations in the rat VTA during stereotypic locomotion
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1
University of Liège, Belgium
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2
Otto-von-Guericke University , Germany
State of mind and behavior result from the simultaneous activity of a large number of neurons. This activity generates rhythms which rapidly fluctuate in neuronal networks during wakefulness. How does the brain coordinate the activity of various networks to produce the appropriate behavioral output? This question is important for both fundamental and applied neuroscience. Dopaminergic psychostimulants turn up to be a scientific tool allowing to modulate the brain state of animals in a way that mimicks some neurological impairments. Behavioral observations and electrophysiolgical recordings performed on freely moving rats in control conditions and after psychostimulant injections may help understand how changes in activity of different brain regions affect behavior.
Cocaine in moderate doses is well known to increase locomotor activity. We previously showed that, in contrast to cocaine alone, co-administration of a low (auto-receptor-selective) dose of quinpirole (0.1 mg/kg, i.p.) and a moderate dose of cocaine (10 mg/kg, i.p.) alters the pattern of locomotor activation, making it look like a so-called locomotor stereotypy. Here, we sought to determine possible network mechanisms of the effect using telemetric recordings of local field potentials (LFPs) within the ventral tegmental area (VTA). This brain region is strongly involved in the regulation of motor activity, motivation, reward and salience. VTA dopaminergic and GABAergic neurons are organized in “subnetworks” with specific inputs and outputs. Our 8-microelectrode-arrays span most of the extent of the VTA, while the telemetric system allows recording LFPs from the freely behaving animals. Our hypothesis was that the altered behavior could be due to changes in the activity of the VTA network. Wistar rats were observed and recorded during baseline and after the intraperitoneal injections of saline, a moderate dose of cocaine (10 mg/kg, i.p.), or co-administration of a low dose of quinpirole (0.1 mg/kg, i.p.) with a moderate dose of cocaine (10 mg/kg, i.p.).
As in the previous experiments, stereotyped pattern of locomotion was observed only after the quinpirole and cocaine co-administration.
Power spectrum analysis of the LPFs revealed a prominent peak in theta frequency range (~7-9 Hz) during locomotor activity. The peak was observed in the baseline as well as after the injections. However, the values of the LFP theta peak were significantly different depending on the experimental conditions. As compared to the baseline, cocaine alone induced a shift of the peak of LFP theta power toward a higher frequency. In contrast, when cocaine was co-administrated with the low-dose of quinpirole, the peak was shifted toward a lower frequency (by ~15%, p<0.001).
Our data show that an auto-receptor-selective dose of quinpirole markedly alters the quality of cocaine-induced locomotion and at the same time significantly slows down the macroscopic rhythm of the VTA network. To our knowledge, this is the first suggestion that a moderate shift in frequency of LFPs in the VTA is associated with a strong behavioral alteration. We hypothesize that this reduced frequency may alter the ability of the VTA to communicate with its output structures.
Acknowledgements
This work was supported by grants n° 3.4533.09 and T. 0015.13 from the F.R.S.-FNRS (VS) and by a grant from the Belgian Science Policy (IAP P7/10) (VS). SK was supported in part by an “Assistant” mandate of the University of Liège. J. Dethier is a Research Fellow of the F.R.S.-FNRS (Belgian Fund for Scientific Research).
Keywords:
Ventral Tegmental Area,
Dopaminergic Neurons,
Telemetry,
Cocaine,
Stereotyped Behavior
Conference:
Belgian Brain Council 2014
MODULATING THE BRAIN: FACTS, FICTION, FUTURE, Ghent, Belgium, 4 Oct - 4 Oct, 2014.
Presentation Type:
Oral Presentation
Topic:
Basic Neuroscience
Citation:
Koulchitsky
S,
Beeken
T,
Monteforte
A,
Dethier
J,
Quertemont
E,
Findeisen
R,
Bullinger
E and
Seutin
V
(2014). Changed state – changed brain: shift of the dominant frequency of theta oscillations in the rat VTA during stereotypic locomotion.
Conference Abstract:
Belgian Brain Council 2014
MODULATING THE BRAIN: FACTS, FICTION, FUTURE.
doi: 10.3389/conf.fnhum.2014.214.00081
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Received:
03 Jul 2014;
Published Online:
02 Sep 2014.
*
Correspondence:
Prof. Vincent Seutin, University of Liège, Liège, Belgium, V.Seutin@ulg.ac.be