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Periaqueductal gray matter stimulation-produced analgesia in diabetic rats
1Department of Pharmacology, Faculty of Pharmaceutical Sciences, Hoshi University, Tokyo, Japan.
Abstract:
The effect of diabetes on periaqueductal gray matter (PAG) stimulation-produced analgesia (SPA) was examined in rats. PAG SPA was assessed using the tail-pinch test. PAG stimulation produced marked analgesia in both naive and diabetic rats. Furthermore, the degree of PAG SPA did not differ between naive and diabetic rats. PAG SPA was significantly attenuated by a low dose (0.5 mg/kg, s.c.) of naloxone in naive rats, but not in diabetic rats. However, a high dose (5 mg/kg, s.c.) of naloxone significantly and equally attenuated PAG SPA in both naive and diabetic rats. On the other hand, the analgesic potency of morphine (3 mg/kg, s.c.) was significantly reduced in diabetic rats as compared with naive rats. These results suggest that PAG SPA in diabetic rats may be mediated by different opioid receptor interactions as compared with naive rats.