Immediate and highly sensitive aversion response to a novel food item linked to AH receptor stimulation.

Aversion to novel food items was studied in male rats and mice after 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) exposure using chocolate consumption as an indicator. The correlation of this phenomenon with susceptibility to acute toxicity and CYP1A1 induction was examined by determining the dose-response of chocolate aversion in differently dioxin-sensitive rat lines after TCDD (0.01-10 μg/kg). Furthermore, the dependence of this behavioral alteration on the AH receptor (AHR) was studied employing AHR-deficient and wild-type mice. We offered chocolate for both species as a novel food item immediately after the exposure, and it was available with standard rodent chow for 3 days. The ED₅₀ value for the extremely resistant rat line A (LD₅₀) value > 10,000 μg/kg) was 0.36 μg/kg, for the semi-resistant line B (LD₅₀) value 830 μg/kg) 1.07 μg/kg and for the TCDD-sensitive line C (LD₅₀ value 40 μg/kg) 0.34 μg/kg. Interestingly, the ED₅₀ values for chocolate aversion were very similar to those for CYP1A1 induction in these rat lines. Findings on AHR-deficient and wild-type mice implied the involvement of the AHR in this intriguing response, which may thus represent a mechanism to restrict exposure to potentially toxic dietary substances causing hepatic induction of drug-metabolizing enzymes.