NICOTINIC ACETYLCHOLINE-RECEPTORS ON CAPSAICIN-SENSITIVE NERVES

TO study the density of nicotinic acetylcholine receptors on primary a fferents and central nociceptive pathways, [H-3](-)-nicotine binding w as conducted in the cerebral cortex and spinal cord including dorsal r oots and ganglia (DRG), of control rats and rats desensitized by neona tal capsaicin treatment. [H-3](-)-nicotine binding in capsaicin-treate d rats was reduced in cerebral cortex by 35% and spinal cord+DRG by 46 % (p<0.05). Functionally, both iontophoretically applied acetylcholine - and capsaicin-evoked flares (measured by laser Doppler flowmetry) we re reduced in capsaicin-treated animals (p<0.05); similarly, electrica l stimulation-evoked nares were significantly lower in the same group, compared with controls (p<0.05). These data provide direct evidence t hat many neuronal nicotinic acetylcholine receptors are associated wit h capsaicin-sensitive peptidergic neurones, including primary afferent s, DRG and central nociceptive pathways.