LONG-TERM EFFECTS OF NEONATAL AXOPLASMIC-TRANSPORT ATTENUATION ON THEORGANIZATION OF THE RATS TRIGEMINAL SYSTEM

The current study examined the long-term effects of infraorbital nerve (ION) axoplasmic transport attenuation with vinblastine on the organi zation of trigeminal (V) primary afferents and central vibrissae-relat ed patterns. Retrograde tracing and single unit recording were used to evaluate the innervation of vibrissae follicles in adult (P > 60) rat s that sustained application of vinblastine to the ION at birth. Singl e units recorded from vinblastine-treated animals yielded responses to deflection of a single vibrissa, and a significantly (P < 0.001) high er percentage of these cells (85.7%) showed rapidly adapting responses compared with normal rats (42.2%). Retrograde tracing revealed a qual itatively and normal distribution of V ganglion cells innervating A-ro w and E-row vibrissae follicles in vinblastine-treated rats. Transgang lionic tracing with horseradish peroxidase (HRP) demonstrated a qualit atively and quantitatively normal somatotopic organization of vibrissa e follicle input to V nucleus principalis (PrV) and V subnucleus inter polaris (SpI) in the vinblastine-treated animals. Despite the nearly n ormal mapping of V ganglion cell axons onto the vibrissae follicles an d brainstem, staining for either cytochrome oxidase (GO) or parvalbumi n failed to reveal vibrissae-related patterns in PrV, SpI, or the magn ocellular portion of V subnucleus caudalis in these animals. Labelling of thalamocortical afferents with HRP and staining for CO also failed to reveal a cortical vibrissae-related pattern in the vinblastine-tre ated rats. The present results indicate that although transient attenu ation of axoplasmic transport with vinblastine has limited effects on the peripheral and central projections of surviving V primary afferent s, it permanently disrupts the normal development and maintenance of c entral vibrissae related patterns. (C) 1997 Wiley-Liss, Inc.