Opioid-Induced Changes in Level of Consciousness

One of the most common and troublesome side effects associated with opioid analgesics is a decreased level of consciousness, commonly referred to as sedation. Yet virtually no research has been done evaluating opioid-induced sedation. The purpose of this study was to describe the effects of two doses of three relatively-selective opioid agonists (i.e., morphine 0.5 ╡g/kg & 500 ╡g/kg, pentazocine 50 ╡g/kg & 5 mg/kg, and naloxone 0.5 ╡g/kg & 500 ╡g/kg) on selected electroencephalograph (EEG) parameters of conscious rats. Experiments were done using 24 adult, male Sprague-Dawley rats weighing between 240 and 260 grams. Rats were surgically implanted with cortical EEG recording electrodes and allowed five days to recover. On the day of the experiment, two hours of baseline EEG recordings were collected before each rat received a subcutaneous injection of normal saline or one of the doses of drug. EEG recordings continued for another four hours for a total recording time of six hours. From three-dimensional graphs of the percent of absolute power attributable to individual one Hz frequency bands for each minute of the 360 minute experiment, cyclic fluctuations in the percent of absolute power at 7 and 8 Hz were observed. When the baseline recording period was compared with the two, two hour recording periods following drug administration, the lower doses of all three opioid agonists significantly increased (p.05 the="" magnitude="" of="" percent="" absolute="" power="" at="" and="" hz.="" these="" data="" provide="" information="" about="" changes="" in="" spectral="" densities="" eeg="" following="" administration="" three="" relatively-selective="" opioid="" agonists.="" results="" this="" study="" suggest="" that="" cyclic="" fluctuations="" hz="" might="" be="" a="" parameter="" indicative="" alterations="" central="" nervous="" system="" functioning="" focus="" future="" research="" investigating="" phenomenon="" opioid-induced="" sedation.="">