M. Unkila et al., DIFFERENTIAL EFFECT OF TCDD ON BRAIN-SEROTONIN METABOLISM IN A TCDD-SUSCEPTIBLE AND A TCDD-RESISTANT RAT STRAIN, Chemosphere, 27(1-3), 1993, pp. 401-406
Two rat strains differ widely (over 300-fold) in their LD50-values for
TCDD. We have compared the effects of TCDD on brain aminergic systems
in the two rat strains to assess the role of these systems in the str
ain difference. Rats of both strains were given 50 mug/kg TCDD (LD100
for Long-Evans [L-E] rats; nonlethal to Han/Wistar [H/W] rats) or vehi
cle. Monoamines were measured 4 or 10 days after the exposure. The was
ting syndrome appeared only in L-E rats after TCDD administration. Fou
r and 10 days after exposure, only L-E rats exhibited ca. 30 - 50 % el
evated levels of the serotonin (5-HT) precursor tryptophan and a 5-HT
metabolite 5-HIAA implying enhanced serotonergic activity by TCDD. Imp
ortantly, food-restricted L-E rats, the resistant H/W rats or H/W rats
subjected to TCDD exposure combined with food restriction did not exh
ibit elevated tryptophan or 5-HIAA concentrations. The turnover of nor
adrenaline or dopamine was not markedly affected in either rat strain
by TCDD. These findings imply that the enhanced central 5-HT turnover
in L-E rats may be associated with the wasting syndrome and acute leth
ality of TCDD.