Abstract
Gurmarin (Gur), a polypeptide isolated from the plant Gymnema sylvestre, is known to selectively inhibit responses of the chorda tympani (CT) nerve to sweet compounds in rodents. In mice, the sweet-suppressing effect of Gur differs among strains. Responses to sweet compounds in the chorda tympani (CT) nerve were inhibited to < 50% of control by Gur in C57BL/6 but only slightly if at all in BALB/c (BALB) mice. These two mouse strains possess different alleles of the sweet receptor gene, Sac (Tas1r3) (taster genotype for C57BL/6 and non-taster genotype for BALB/c mice). This raises the possibility that polymorphisms of Tas1r3 may account for differential sensitivity to Gur.To investigate this possibility, we examined the effect of Gur on CT responses to sweet compounds in another Tas1r3 non-taster strain, 129X1/Sv mice. Our results indicated that this non-taster strain exhibited significant inhibition by Gur of CT responses to various sweet compounds similar to that observed in C57BL mice having the Tas1r3 taster genotype. This suggests that the mouse strain difference in the Gur inhibition of sweet responses of the CT nerve may not be associated with polymorphisms of Tas1r3. [J Physiol Sci. 2007;57 Suppl:S103]
