Chronic administration of sublethal doses of carbaryl increases pineal N‐acetyltransferase and hydroxyindole‐O‐methyltransferase activities and serum melatonin levels

Attia AM, Reiter RJ, Withyachumnarnkul B, Mostafa MH, Soliman SA, El‐sebae A.‐K.H. Chronic administration of sublethal doses of carbaryl increases pineal N‐acetyltransferase and hydroxy‐0‐ rnethyltransferase activities and serum melatonin levels. J Pineal Res 1 99 1 1 0149‐54. The purpose of this study was to examine the effects of chronic administration of sublethal doses of carbaryl on pineal melatonin synthesis. N‐methyl 1‐naphthylcarbamate (carbaryl) (8.33 mg/kg B.W. daily) was administered orally to adult male albino rats for 6 successive days. Nocturnal (0100) N‐acetyltransferase and hydroxyindole‐0‐methyltransferase activities were increased (roughly 75% and 60%, respectively) by carbaryl administration; likewise, carbaryl augmented serum melatonin levels at 2300. Pineal tryptophan, 5‐hydroxytryptophan, serotonin, and 5‐hydroxindole acetic acid levels were unaffected at all three time points. The results indicate that the carbamate pesticide, i.e., carbaryl, modifies pineal melatonin synthesis in vivo.