The Effect of Capsaicin Pretreatment on the Cystometrograms of Urethane Anesthetized Rats

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Abstract
Administration of capsaicin to newborn rats produced a slight but significant increase in bladder weight and markedly altered the cystometrograms of urethane anesthetized rats. In particular capsaicin pretreatment significantly increased micturition threshold. In many of these preparations the bladders exhibited a hypertonic response to saline filling; the flat phase of the cystometrogram was not observed. Capsaicin pretreatment of adult animals increased micturition threshold up to 1 mo. from capsaicin administration. In these preaparations a flat volume-pressure relationship preceded micturition contractions. Administration of capsaicin to both newborn and adult animals did not alter the amplitude of micturition contractions. Intravesical instillation of capsaicin had an acute excitatory effect on the responsiveness of the urinary bladder to reflex activation. Capsaicin pretreatment produces a functional impairment of the sensory branch of micturition reflexes and a capsaicin-sensitive mechanism(s) is involved in the regulation of micturition threshold.