Adaptation to repeated cocaine administration in rats.

Authors:
Dr. Zbigniew K Binienda, DVM, PhD
Dr. Zbigniew K Binienda, DVM, PhD
FDA/NCTR
Research Scientist
Neurophysiology; Neurotoxicology
Little Rock, AR | United States

Ann N Y Acad Sci 2002 Jun;965:172-9

Division of Neurotoxicology, NCTR/FDA, Jefferson, Arkansas 72029, USA.

Quantitative electroencephalogram (EEG) studies in cocaine-dependent human patients show deficits in slow-wave brain activity, reflected in diminished EEG power in the delta and theta frequency bands. In the present study, electrophysiological measures were monitored in 10 nonanesthetized, adult male Sprague-Dawley rats via bipolar, epidural electrodes implanted over the somatosensory cortex. Control electrocorticograms (ECoG) were recorded twice within a two-week interval to establish a baseline. Rats were subsequently injected daily with cocaine HCl at 15 mg/kg, i.p., for two weeks. The ECoG was recorded during a 1-h session one day after the last injection. Total concentrations of dopamine (DA) and its metabolites were assayed in caudate nucleus (CN) and frontal cortex (FC) using HPLC/EC. Compared with controls, marked increases in DA concentrations were observed in both regions. The DA turnover decreased significantly. The power spectra, obtained by use of a fast Fourier transformation, revealed a significant decrease in slow-wave delta frequency bands following repeated exposure to cocaine. These data are consistent with reported findings in humans that repeated exposures to cocaine result in a decrease in slow-wave brain activity. Further studies are necessary to establish whether regional alterations in blood flow and metabolic activity may underlie such observations.

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http://dx.doi.org/10.1111/j.1749-6632.2002.tb04159.xDOI Listing
June 2002
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