Tryptophan Adjunctive Therapy To Conventional Haloperidol Treatment In Schizophrenia: Effects On Serotonergic Mechanisms In Rat Brain

Abstract

We studied the effects of dietary amino acid L-tryptophan (TRP) as an adjunct to haloperidol administration on the modulation of extrapyramidal symptoms (EPS) and rat brain serotonin (5-hydroxytryptamine; 5-HT) functions in relation to schizophrenia. TRP added in the drinking water and haloperidol at doses of 5.0 mg/kg or saline were injected for two weeks twice daily with one week of withdrawal to 36 locally bred male albino Wistar rats. Motor/ Exploratory activities were scored in activity boxes and open field apparatuses. Catalepsy was monitored on an inclined surface. Results revealed significant increases (p<0.01) in locomotor activity and marked reduction in catalepsy in rats orally supplemented with TRP for 3 weeks plus haloperidol administration. Significant (p<0.01) increases were observed in the rat brain TRP and 5-HT metabolism. The findings suggest that amino acids, in particular, TRP can possibly attenuate EPS functions induced by haloperidol and enhanced brain 5-HT metabolism.