THE JOURNAL OF COMPARATIVE NEUROLOGY zyx 352:308-320 (1995) Birth Dates and Survival After Axotomy of Neurochemically Defined Subsets of Trigeminal Ganglion Cells FLETCHER A. WHITE, NICOLAS L. CHIAIA, GORDON J. MACDONALD, AND ROBERT W. RHOADES Department of Anatomy, Medical College of Ohio, Toledo, Ohio 43699 (F.A.W., N.L.C., R.W.R.); Department of Anatomy and Neurobiology, Robert Wood Johnson Medical School, Piscataway, New Jersey 08854 (G.J.M.) ABSTRACT Trigeminal (V) ganglion cells with different neurochemical phenotypes or different birth dates are affected differently by neonatal axonal transection. The aim of the present study was to determine if V ganglion cell birth date and neurochemical phenotype were correlated and if these two variables could be related to responses to neonatal axonal transection. Immunocyto- chemistry, histochemistry, and [3H]thymidine labelling were used to determine the birth dates of V ganglion cells recognized by antibodies directed against neurofilament protein (NF), calcitonin gene-related peptide (CGRP), and substance P (SP) and those that bound the lectin Bandierea simplicifolia-I (BS-I).All V ganglion cells were born between embryonic days (E-)9.5 and 14.5. All ganglion cells were born between E-9.5 and E-14.5. In a normalized population (percentages normalized to equal loo%), over 90% of NF-positive V ganglion cells were born between E-10.5 and E-12.5. The majority of CGRP-positive and SP-positive ganglion cells zyx (> 90%)were generated from E-13.5 to E-14.5 and E-12.5 through E-14.5, respectively. Almost 85% of BS-I-positive ganglion cells were generated on E-12.5 through E-14.5. Previous results and additional data from this study indicated that NF- and BS-I-positive ganglion cells are proportionally more likely to be lost after neonatal axotomy and that SP-positive cells are more likely to remain. The percentage of CGRP-positive cells in the V ganglion was not significantly altered by neonatal infraorbital nerve transection. Overall, these findings do not indicate a strong relationship between cell birth date and the probability of survival after neonatal axonal damage for all V ganglion cell phenotypes. Indexing terms: neurogenesis, cell death, immunocytochemistry, plasticity zyxw o 1995 Wiley-Liss, Inc. Peripheral nerve damage in infancy results in the death of a large percentage of injured ganglion cells, but many neurons survive such damage (see, e.g., Aldskogius and Risling, 1981; Savy et al., 1981; Risling et al., 1983; Bondok and Sansone, 1984; Heath et al., 1986; Chiaia et al., 1987). Transection of the infraorbital nerve [ION, the trigeminal (V) branch innervating the mystacial vibrissae follicles] results in the loss of approximately two-thirds of the cells that contribute axons to it (Chiaia et al., 1987). Previous reports from this laboratory have suggested that not all ganglion cell populations are affected to the same degree by neonatal ION transection. Enfiejian et al. (1989) showed that ION transection at birth reduced the absolute number of V ganglion cells that were immunoreactive for substance P (SP) but increased their relative percentage in the ganglion. In contrast, White et al. (1990) observed that neonatal ION transection resulted in a marked decrease in the relative percentage of a nearly mutually exclusive population of V ganglion cells that bound the lectin Ban- dierea simplicifolia-I (BS-I). More recently, White et al. (1993a) reported a significant relationship between V gan- glion cell birth date and survival after neonatal axonal damage. They noted that V ganglion cells born late in gestation, on E-12.5 through E-14.5, were significantly more likely than early-born (E-9.5 through E-11.5) cells to survive neonatal axotomy. The combination of these results with those provided by Enfiejian et al. (1989) and White et al. (1990) suggested to us that ganglion cells with different phenotypes may have different distributions of birth dates, Accepted August 10,1994 Address reprint requests to Fletcher A. White, Department of Anatomy, Medical College of Ohio, CS #10008, Toledo, OH 43699. Q 1995 WILEY-LISS, INC.