Nociception and opioid-induced analgesia in lean (Fa/-) and obese (fa/fa) Zucker rats.
Previous research indicates a possible interrelationship between the endogenous opioids (EO), nociception and food-intake. We therefore considered the hyperphagic obese Zucker rat a good candidate for abnormal responses to nociceptive stimuli. Pairs of lean and obese sisters were tested for latency of response to nociceptive stimuli by tail-flick and tail-pinch methods. Obese rats exhibited shorter latencies in each test, (tail-flick, p less than 0.05 and tail-pinch, p less than 0.001). Dose/response curves for morphine analgesia indicate that morphine is less potent in obese than in lean rats (ED50's = 4.87 +/- 0.62 mg/kg and 3.12 +/- 0.41 mg/kg respectively, p less than 0.05). These data suggest a defect in the EO systems of obese Zucker rats.
D000818:Animals; D004435:Eating; D004723:Endorphins / Q000502:physiology*; D005260:Female; D009020:Morphine; D009765:Obesity / Q000503:physiopathology*; D010146:Pain / Q000503:physiopathology*; D010147:Pain Measurement; D051381:Rats; D011924:Rats, Zucker; D011930:Reaction Time / Q000502:physiology
D004723:Endorphins; D009020:Morphine