ABSTRACT
The intra-plantar injection of carrageenan elicited an inflammatory response characterized by increase of the paw thickness and infiltration of neutrophils in paw tissues. Histidine, n-acetylcysteine and diclofenac decreased paw thickness, and neutrophil infiltration in the paw tissues. The anti-inflammatory effect induced by co-administration of histidine and n-acetylcysteine with diclofenac, was more than that obtained from histidine and n-acetylcysteine administered alone. The results suggested that histidine, n-acetylcysteine and diclofenac produced anti-inflammatory activities by reducing paw edema and neutrophil infiltrationin induced by carrageenan. Inhibition of cyclooxygenase products such as prostaglandins may be involved in the anti-inflammatory effects induced by histidine and n-acetylcysteine.
ABSTRACT
In the present study, effects of intracerebroventricular (icv) administration of histamine, mepyramine (H1-receptor antagonist) and famotidine (H2-receptor antagonist) have been investigated on the formalin test in rats. Subcutaneous injection of formalin (50 μl, 1%) into the ventral surface of the left hind paw produced a marked biphasic pain response (first phase: 0–5 min and second phase: 15–45 min). All the performed treatments did not significantly influence the first phase of pain. Histamine at the doses of 10 and 40 μg and mepyramine and famotidine at the same doses of 20 and 80 μg, significantly (P<0.05) decreased the late phase of formalin-induced pain. Pretreatments with mepyramine and famotidine at the same dose of 80 μg, significantly (P<0.05) prevented the histamine (40 μg)-induced antinociception. These results indicate that brain histamine produces antinociception, and both central H1 and H2 receptors may involve in the histamine-induced antinociception in the formalin test in rats.