Cholecystokinin octapeptide alters morphine-induced effects on EEG power spectra both quantitatively and...

In the present study, EEG analysis was used to determine if cholecystokinin octapeptide (CCK-8) has an effect on the EEG spectral profile associated with morphine-induced bursting. Adult female Sprague-Dawley rats were implanted with cortical electrodes and indwelling i.c.v. and i.v. cannulas. On the day of the experiment, each rat received an i.c.v. injection of either H2O or one of four doses of CCK-8: 8.0, 16.0, 32.0 or 64.0 ng. Ten minutes after receiving the i.c.v. injection, each rat received a 10.0 mg/kg dose of morphine by i.v. injection. Neither the i.c.v. injections of H2O nor CCK-8 produced any EEG bursting or behavioral stupor. However, the i.v. injection of morphine produced high-voltage, slow-wave EEG bursts in all rats. Analysis of EEG recorded during bursting showed that both the 32.0 and 64.0 ng doses of CCK-8 increased absolute power associated with morphine-induced bursting, and comparison of the distribution of power across the range of frequency bands between the control (H2O) and the 32.0 ng dose of CCK-8 revealed that CCK-8 caused a significant change in the pattern of distribution of power. Furthermore, significant dose-related differences were found in the global (1-50 Hz) parameters absolute power, mean frequency, mobility, complexity and edge frequency. Significant differences among the five groups were not found in the parameter of peak frequency, or in either latency to slow-wave sleep or duration of morphine-induced bursting. These results demonstrate that CCK-8 caused both quantitative and qualitative changes in the EEG spectral profile associated with morphine-induced bursting.