Dorsal root ganglion neurons with central processes in both dorsal and ventral roots

Evidence that endogenous beta nerve growth factor is responsible for the collateral sprouting. but not the regeneration, of nociceptive axons in adult rats. ---J. Diamond, M. Coughhn, I,. MacIntyre. M. Holmes and B. Visheau, Proc. Natl. Acad. Sci. (U.S.A.). 84 (1987) 6596 66W. Rats and mice were daily injected subcutaneously with rabbit polyclonal antisera raised against mouse 2.5s nerve growth factor (anti-NGF). Cutaneous nociceptor innervatjon was assessed by applying appropriate stimuli to the skin of the hack, and measuring reflex contraction of the underlying cutaneous trunci muscle. Anti-NGF treatment prevented the collateral sprouting of mechanical and heat sensitive nociceptive afferents into denervated areas of skin. Following withdrawal of anti-NGF. collateral sprouting proceeded apace. In contrast, anti-NGF did not affect fiber regeneration after nerve crush in either intact or dorsal rhizotomized animals. Regeneration was assessed histoiogically, by Evans blue extravasation. and by electrophysio~ogical recordin g. These two modes of axonal growth. collateral sprouting and regeneration, appear to be regulated bv different molecular mechanisms. Dorsal root ganglion neurons with central processes in both dorsal and ventral roots. ~~K. Chung and H.S. Kang, Neurosci. L&t., 80 (1987) 202-206. The fluorescent dyes diamino yellow dihydrochioride and true blue. which are transported retrogradely with the axoplasntic flow, were applied to the distal cut ends of dorsal and ventral roots L6 and Sl in rats. Substantial numbers of neurons were labeled from the ventral root, and about a third of these were also labeled (i.e., double labeled) from the dorsal root. This indicates that the double labeled cells had branches in both ventral and dorsal roots. Such cells were small to medium in diameter. Controls included cutting the root between the dye application site and the DRG and confirming that labeling was thus prevented. No topographic layout within the DRGs was identified. The data presented do not allow one to know whether any afferent fibers in ventral roots enter the spinal cord along the ventral root, or alternatively innervate the meninges. make U-turns and exit, or end blindly. Also see the related paper: Kim J.. Shin. H.K. and Chung, J.M.. Many ventral root afferent cat are third branches of dorsal root ganglion cells, Brain Res., 417 (1987) 304--314.

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In vivo anti-NGF induces sprouting of sensory axons in dorsal roots. ~ C.E. Hulsebosch, J.R. Perez-Poto and R.E. Coggeshall, J. Comp. Neural., 259 (1987) 445451. Newborn rats were treated daily with rabbit antibodies raised against mouse P-NGF. Counts of cells in the T4-T6 dorsal root ganglia showed a decline of 38% compared to normal littermates. However, there were 17% more myelinated fibers and 40% more unmyelinated fibers in the corresponding dorsal roots. There has apparently been an increase in the average number of afferent fibers per ganglion cell. Functional characteristics of lumbar visceral afferent fibres from the urinary bladder and the urethra in the cat. ~ E. Bahns, U. Ernsberger, W. Janig and A. Nelke, Pfliigers Arch., 407 (1986) 510-518. Single afferent axons innervating the urinary bladder or urethra were isolated from lower lumbar white rami or from lumbar splanchnic nerves by microdissection. All were thin myeiinated or unmyelinated, and most had Iow levels of ongoing activity (0.2-l ips). Receptive fields were single mechanosensitive sites on the visceral surface. For bladder fibres, responses were graded to passive distension and isovolumetric contraction of the bladder. The results do not support the notion that noxious events in the urinary bladder are encoded by ‘specific’ nociceptive visceral afferents. Sodium and potassium currents in acutely demyefinat~ internodes of rabbit sciatic nerves. - S.Y. Chiu and W. Schwarz, J. Physiol. (Lond.), 391 (1987) 631-649. A fundamental tenet about the functional architecture of myelinated axons is that voltage dependent sodium channels are concentrated at nodes of Ranvier and that the internodal axolemma is essentially