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Electrophysiological properties of dopamine neurons in the ventral tegmental area of Sardinian alcohol-preferring rats

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Abstract

Rationale

Sardinian alcohol-preferring (sP) or -nonpreferring (sNP) rats are one of the few pairs of lines of rats selectively bred for their voluntary alcohol preference or aversion, respectively. Ventral tegmental area (VTA) dopamine (DA) neurons have long been implicated in many drug-related behaviors, including alcohol self-administration. However, the electrophysiological properties of these cells in sP and sNP rats remain unknown.

Objectives

This study was designed to examine the properties of posterior VTA DA neurons and to unveil functional differences between sP and sNP rats.

Materials and methods

The electrophysiological properties of DA cells were examined performing either single-cell extracellular recordings in anesthetized rats or whole-cell patch-clamp recordings in slices.

Results

Extracellular single-unit recordings revealed an increased spontaneous activity in sP rats. However, a corresponding difference was not found in vitro. Moreover, DA cells of sP and sNP rats showed similar intrinsic properties, suggesting changes at synaptic level. Therefore, inhibitory- and excitatory-mediated currents were studied. A decreased probability of GABA release was found in sP rats. Additionally, sP rats showed a reduced depolarization-induced suppression of inhibition, which is an endocannabinoid-mediated form of short-term plasticity. Additionally, the effect of cannabinoid-type 1 (CB1) receptor agonist WIN55,212-2 on GABAA IPSCs was smaller in sP rats, suggesting either a reduced number or functionality of CB1 receptors in the VTA.

Conclusions

Our findings suggest that both decreased GABA release and endocannabinoid transmission in the VTA play a role in the increased impulse activity of DA cells and, ultimately, in alcohol preference displayed by sP rats.

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Acknowledgments

We thank W.T. Dunn for proofreading the manuscript. This work was supported by the grant PRIN 2005 (MIUR).

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Author notes

  1. Simona Perra

    Present address: Waggoner Center for Alcohol and Addiction Research, Section of Neurobiology and Institute for Neuroscience, University of Texas, Austin, TX, USA

Authors and Affiliations

  1. “B.B. Brodie” Department of Neuroscience, University of Cagliari, Cittadella Universitaria di Monserrato, 09042, Monserrato, Italy

    Miriam Melis, Giuliano Pillolla, Simona Perra & Marco Pistis

  2. Centre of Excellence “Neurobiology of Addiction”, University of Cagliari, 09042, Monserrato, Italy

    Miriam Melis, Giuliano Pillolla, Simona Perra, Anna Lisa Muntoni & Marco Pistis

  3. C.N.R. Institute of Neuroscience, 09042, Monserrato, Italy

    Giancarlo Colombo & Anna Lisa Muntoni

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  1. Miriam Melis
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Correspondence to Miriam Melis.

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Melis, M., Pillolla, G., Perra, S. et al. Electrophysiological properties of dopamine neurons in the ventral tegmental area of Sardinian alcohol-preferring rats. Psychopharmacology 201, 471–481 (2009). https://doi.org/10.1007/s00213-008-1309-2

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  • DOI: https://doi.org/10.1007/s00213-008-1309-2

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