Abstract
The respiratory effects evoked by systemic injection of bombesin were studied in spontaneously breathing rats that were (i) neurally intact and subsequently bilaterally vagotomized, (ii) intact, before and after pharmacological blockade of the bombesin BB 1 and BB 2 receptors. An intravenous bolus of bombesin (10 μg/kg) evoked sighs, decrease in the breathing rate, augmentation of tidal volume and an increase in mean arterial blood pressure. Midcervical vagotomy abolished all respiratory changes evoked by bombesin challenge, but did not prevent the increase in blood pressure. Blockade of BB 1 and BB 2 receptors with an intravenous dose of 50 μg/kg of [D-Phe] 12-bombesin, reduced significantly the cardio-respiratory effects due to bombesin administration. The BB 1 receptors antagonist, BIM 23127, at a dose of 100 μg/kg did not block the response to bombesin. These results indicate that bombesin given systemically stimulates ventilation by activation of BB 2 receptors affecting mainly the tidal component of the breathing pattern, and that the response is mediated by the lung vagi. The hypertensive effect of bombesin resulted from the excitation of BB 2 receptors, but occurred outside vagal afferentation from the lungs.
Published Version
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