The Sensitivity of the Axon Reflex in Term and Premature Infants

The criteria currently used for assessing the maturity and physiologic age of the newborn includes birthweight, gestational age, and clinical impression. Since the progressive development of the peripheral nervous system in the newborn appears to be more closely related to gestational age, rather than age after birth (1), a new measure of maturation based on this factor seemed to promise a more quantitative approach. We therefore investigated the axon reflex in a group of infants, and attempted to relate the characteristics of this nerve dependent response to the general, gross indices of maturity.The second part of Lewis's “triple response, the axon reflex, is mediated by anti-dromic stimulation of sensory nerves, with a resultant vasodilation of the arterial cutaneous blood vessels (2). This reflex requires an intact and functional peripheral nerve network. A quantitative evaluation of this response was investigated in term and premature infants by means of histamine in divided doses.MATERIALS AND METHODSAs a standard, histamine sensitivity was tested in a group of 11 healthy young adults. Each received 5 injections of histamine acid phosphate; expressed in equivalent concentrations of histamine base, these ranged from 1 X 10 * to 1 X 10 1. Robinson, R. J. and Tizard, J. P. M: Central nervous system of the newborn. Brit. Med. Bull., 22:49,1966.