Effect of the infraorbital nerve transection on the sensory input subsystem in the masticatory system of newborn mice.

Abstract

To confirm a hypothetical idea that the masticatory system will play a fundamental function in the postnatal growth of the body, the centripetal mastication-related information flowing in the system was interrupted by cutting the infraorbital nerve on the newborn mice. The sham- and axotomy-operation mice were returned to their mother. 20 days after the operation the sensory input unit was studied in the serial frontal section histologically. On the other hand the body weight was measured every 5 days after the operation and the significant level was examined statistically. The results obtained are as follows: 1) The sensory input units (primary and secondary sensory neurons) have completely reduced to disappear in situ. 2) The significant differences between both groups were seen at the level of P less than 0.001 from the period of 20-day after the operation. In comparison with that of the sham-operation mice, the axotomy-operation mice have decreased about 20 to 30% in the body weight and so reduced in shape, characterized by the smaller head, a shorter trunk and limbs and a shorter, thinner tail. The experimental data suggest that the centripetal mastication-related information plays an important role in the postnatal growth of the masticatory system and the other functional systems of the body.