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The reduction of antinociceptive effect of morphine administered intraventricularly is correlated with the decrease
1Department of Pharmacology, College of Medicine, Hallym University, Chunchon, Kwangwon-Do, S. Korea.
Abstract:
1. The antinociceptive effect of morphine (25 micrograms) administered into the 3rd ventricle was significantly attenuated in streptozotocin-induced diabetic rats as measured by the tail-flick assay. 2. The release of serotonin (5-HT; 5-hydroxytryptamine) from the spinal cord caused by intraventricular injection of morphine (25 micrograms) was significantly reduced in streptozotocin-induced diabetic rats. 3. No differences of 5-HT contents of the spinal cord (lumbar cord) between streptozotocin-induced diabetic- and vehicle-treated rats were found. 4. It is concluded that the reduction of antinociception produced by intraventricular injection of morphine in streptozotocin-induced diabetic rats might be, at least partly, due to the decrease of 5-HT release from the spinal cord.