Published in

The Company of Biologists, Disease Models and Mechanisms, 2017

DOI: 10.1242/dmm.026682

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Long-lasting memory deficits in mice withdrawn from cocaine are concomitant to neuroadaptations in hippocampal basal activity, GABAergic interneurons and adult neurogenesis

This paper is made freely available by the publisher.
This paper is made freely available by the publisher.

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Abstract

The cocaine addiction disorder is notably aggravated by concomitant cognitive and emotional pathology that impedes recovery. We studied whether a persistent cognitive/emotional dysregulation in mice withdrawn from cocaine holds a neurobiological correlate within the hippocampus, a limbic region with a key role in anxiety and memory but that has been scarcely investigated in cocaine addiction research. Mice were submitted to a chronic cocaine (20 mg/kg/day for 12 days) or vehicle treatment followed by 44 drug-free days. Some mice were then assessed on a battery of emotional (elevated plus-maze, light/dark box, open field, forced swimming) and cognitive (object and place recognition memory, cocaine-induced conditioned place preference, continuous spontaneous alternation) behavioral tests, while other mice remained in their home-cage. Relevant hippocampal features [basal c-Fos activity, GABA+, parvalbumin (PV)+ and neuropeptide Y (NPY)+ interneurons, and adult neurogenesis (cell proliferation and immature neurons)] were immunohistochemically assessed 73 days after the chronic cocaine or vehicle protocol. The cocaine-withdrawn mice showed no remarkable exploratory or emotional alterations but were consistently impaired in all the cognitive tasks. All the cocaine-withdrawn groups, independently of whether they were submitted to behavioral assessment or not, showed enhanced basal c-Fos expression and increased number of GABA+ cells in the dentate gyrus. Moreover, the cocaine-withdrawn mice previously submitted to behavioral training displayed a blunted experience-dependent regulation of the dentate gyrus' PV+ and NPY+ neurons, and adult hippocampal neurogenesis. Results highlight the importance of hippocampal neuroplasticity for the ingrained cognitive deficits present during chronic cocaine withdrawal.