Central effects of neuropeptides on ventilation in the rat

We have examined the effects of centrally applied neuropeptides on ventilation (respiratory rate, tidal volume, and minute ventilation) in urethane-anesthetized rats. TRH caused an increase in respiratory rate, a decrease in tidal volume, but an increase in net minute ventilation. One TRH metabolite, acid TRH, caused similar changes, but no effect was observed from the other TRH metabolite, cHis-Pro. Both bombesin and calcitonin caused increases in minute ventilation due to increases in respiratory rate and tidal volume. Additionally, bombesin induced periodic sighing respirations at rates up to 15/minute which was observed with no other neuropeptide. Substance P, somatostatin, and neurotensin had no effect upon ventilation variables.