EFFECTS OF POSTNATAL ANTI-NGF ON THE DEVELOPMENT OF CGRP-IR NEURONS IN THE DORSAL-ROOT GANGLION

Experiments were undertaken to examine anatomical correlates of physio logical effects of rabbit sera raised against nerve growth factor (ant i-NGF) on nociceptive afferents. This antiserum has been shown to depl ete the population of A-delta high threshold mechanoreceptors and to r educe neurogenic vasodilatation. Because numerous studies implicate ca lcitonin gene related peptide (CGRP)-containing sensory neurons in the se effects, immunocytochemical and anatomical techniques were used to examine the normal development of CGRP-immunoreactive (-IR) neurons in the dorsal root ganglion (DRG) of rats from 13 days to 19 weeks of ag e, and to compare this to the development in rats treated neonatally ( postnatal days 2-14) with anti-NGF. In controls the rate of increase i n the mean diameter of CGRP-IR cells was substantially greater between 13 days and 5 weeks of age than it was between 5 weeks and 19 weeks, in contrast to CGRP-negative neurons whose rate of growth remained rel atively constant. Anti-NGF had no significant effect on growth rate, b ut rats treated with anti-NGF exhibited a reduced proportion of CGRP-I R neurons at 5 weeks. This deficit was reversed by 19 weeks unlike the physiological changes. These results indicate independent regulation of CORP expression and nociceptor physiology by NGF. (C) 1998 Wiley-Li ss, Inc.