Pain
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This study characterized the excitatory (nociceptive) and desensitizing (antinociceptive) properties of the natural pungent substances, capsaicin (CAP) and resiniferatoxin (RTX) instilled in the bladder (intravesical, i.ves.) via an indwelling cannula in awake, freely moving rats. The incidence of 9 behaviors was scored for 10 min following i.ves. vehicle or RTX (1.0 nmol). Abdominal licking and head-turning occurred significantly more often in RTX-treated rats compared to vehicle controls, whereas head-grooming, locomotion, rearing and biting did not differ between the two groups. ⋯ This study demonstrates that repeated application of both CAP and RTX into the bladder produces behavioral effects indicative of local sensory afferent desensitization. I.ves. CAP and RTX appear to produce their excitatory and desensitizing effects via a common mechanism, which is dependent on cation channel activation.(ABSTRACT TRUNCATED AT 400 WORDS)