Ventilatory responses of dystrophic and control hamsters to naloxone

In this study we determined if endogenous opioid peptides may contribute to the depression of ventilation seen in dystrophic hamsters. Ventilation of control and dystrophic awake hamsters was determined prior to either naloxone (1 mg/kg) or saline administration and then 5, 15 and 30 minutes postinjection. Subsequently, animals were exposed to a hypercapnic challenge (7% CO2 in O2). Control hamsters increased ventilation significantly (p less than 0.01) after naloxone compared to saline treatment. In contrast, dystrophic hamsters showed no difference in ventilation when they received either naloxone or saline. Both groups increased ventilation significantly (p less than 0.05) after hypercapnic challenge, whether they had received naloxone or saline. Although dystrophic hamsters can respond to a ventilatory stimulant (CO2), naloxone did not increase ventilation, possibly indicating that endogenous opioids are not responsible for their depressed ventilation.