Abstract
The role of melatonin in altering cell-mediated nonspecific immune responses has been documented in mammals, but there is no report available in reptiles. We designed the present study to evaluate the role of melatonin in altering innate immune responses of leukocytes in freshwater snakes. We administered melatonin injections (dose: 5 and 10 μg/g body weight) during evening hours. Animals receiving saline served as controls. Snakes were sacrificed after 10 and 20 days. We studied the alteration in total and differential leukocyte counts, blood neutrophil phagocytosis, nitric oxide production, superoxide production, and lymphoproliferation. We did not observe a consistent and significant change in total leukocyte count, whereas monocyte, eosinophil, and basophil counts were increased in response to melatonin. Interestingly, the phagocytic response of neutrophils was inhibited when treated with melatonin. Nitrite release and superoxide production by leukocytes were significantly higher in snakes receiving melatonin injections. Exogenous melatonin also enhanced the mitogen-induced lymphocyte proliferation in a manner dependent on dose and duration of melatonin treatment.
