AUTORADIOGRAPHIC MAPPING OF [H-3] SUMATRIPTAN BINDING IN CAT BRAIN-STEM AND SPINAL-CORD

In vitro autoradiography was performed on sections of cat brain stem and spinal cord using [H-3]sumatriptan. Localization studies using 20-25 nM [H-3]sumatriptan showed specific binding to cells in the trigeminal nucleus caudalis and nucleus tractus solitarius of the brain stem and the dorsal horn of the spinal cord. This binding was unaffected by 8-hydroxy-dipropylaminotetralin (20 nM), but was abolished by 5-carboxamidotryptamine (200 nM). Ketanserin displaced total specific binding in the brain stem with a pIC(50) of 6.2 but no apparent regional specificity. These results indicate that [H-3]sumatriptan labels predominantly 5-HT1D alpha and/or 5-HT1D beta (but not 5-HT1A or 5-HT1F) receptor subtypes in cat brain stem and spinal cord.