Carbaryl-induced changes in indoleamine synthesis in the pineal gland and its effects on nighttime serum melatonin concentrations

A. M. Attia, R. J. Reiter, K. O. Nonaka, M. H. Mostafa, S. A. Soliman, A. H. El-Sebae

Research output: Contribution to journalArticle

6 Scopus citations


The effects of different doses of chronically administered carbaryl on rat pineal N-acetyltransferase (NAT) activity, hydroxyindole-O-methyltransferase (HIOMT) activity and pineal and serum melatonin levels during darkness (2300 h and 0100 h) when pineal melatonin synthesis is high were studied. Additionally, pineal levels of 5-hydroxytryptophan (5-HTP), serotonin (5-HT) and 5-hydroxyindole acetic acid (5-HIAA) were estimated. Carbaryl was administered at total doses (over 6 days) of either 50, 125 or 250 mg/kg by gastric gavage. Control rats received vehicle (corn oil) only. During the study, the rats were exposed to light/dark cycles of 14:10 with lights off at 2100 h. Pineal NAT and HIOMT activities and pineal melatonin were increased at 0100 h following carbaryl administration at all three doses. Conversely, serum melatonin was increased at 2300 h after the 250 mg/kg dose of carbaryl while all three doses of the pesticide reduced serum melatonin levels at 0100 h. Pineal 5-HTP, 5-HT and 5-HIAA levels were usually increased at 2300 h but unaffected at 0100 h. The results indicate that carbaryl has significant effects on pineal melatonin synthesis and secretion.

Original languageEnglish (US)
Pages (from-to)305-314
Number of pages10
Issue number3
StatePublished - Jan 1991



  • Carbaryl
  • Hydroxyindole-O-methyltransferase activity
  • Indolamines
  • Melatonin
  • N-acetyltransferase activity
  • Pineal gland
  • Serotonin

ASJC Scopus subject areas

  • Toxicology

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