DIFFERENTIAL-EFFECTS OF PERIPHERAL MANIPULATIONS ON VIBRISSAE-RELATEDPATTERNS IN THE TRIGEMINAL BRAIN-STEM

The expression of galanin and neuropeptide Y (NPY) by primary afferent neurons, including those in the trigeminal (V) system, is markedly up -regulated after peripheral nerve damage and might be expected to infl uence the response of central somatosensory cells to such damage. In t he present study, we assessed the effects of four manipulations that h ave been used to study development and maintenance of vibrissae-relate d patterns in the V system-nerve transection, whisker clipping, activi ty blockade with tetrodotoxin (TTX), and axoplasmic transport attenuat ion with vinblastine-upon the expression of galanin and NPY by V gangl ion cells and their central axons in the V brainstem complex. Both neo natal transection of the infraorbital nerve (ION) and application of v inblastine to it resulted in a marked up-regulation of galanin and NPY in V ganglion cells and their central axon arbors in animals killed o n postnatal day 6. Neither whisker clipping nor application of TTX to the ION produced such changes. Both ION transection and application of vinblastine to this nerve resulted in a loss of vibrissae-related cel lular patterns in the brainstem, but ?TX application and whisker clipp ing did not. These results raise the possibility that up-regulation of galanin and NPY may play a role in the disappearance of vibrissae-rel ated cellular patterns in the brainstem of rats that sustain neonatal ION damage.