Tachykinin receptor (NK1, NK2, NK3) binding sites in the rat caudal brainstem following neonatal capsaicin administration

Binding of [125I]-Bolton–Hunter substance P ([125I]-BHSP), [125I]-neurokinin A and [3H]-senktide to tachykinin NK1, NK2 and NK3 receptors, respectively, was examined in caudal brainstem sections of 10-week-old rats pretreated as neonates (P2) with capsaicin (50 mg/kg, s.c.) or vehicle. [125I]-BHSP binding was localised to the nucleus of the solitary tract (NTS), hypoglossal nucleus and inferior olivary complex, whereas [125I]-neurokinin A and [3H]-senktide binding were confined to the NTS. The distribution and density of binding sites were similar in vehicle- and capsaicin-pretreated rats, suggesting that sensory neuron ablation by neonatal capsaicin does not affect tachykinin receptor numbers in the rat caudal brainstem.