Abstract
Background: It has been shown by various workers that intra-arterial (i.a.) instillation of algogens produced reflex cardiorespiratory (CVR) changes in anesthetized rats, substantiating the role of medium sized peripheral blood vessels in regulation of CVR system.

Aim and Objective: The aim of this study was to understand the role of vagus nerve in algogen- induced vasosensory reflex responses altering CVR parameters.

Material and Methods: Femoral artery was cannulated retrogradely and was utilized for the instillation of saline/bradykinin and recording of blood pressure (BP), using a double-ported 24G cannula. BP, respiration and electrocardiogram were recorded for 30 min after instillation of bradykinin with or without vagotomy. Bradykinin (1 μM) was used as an algogen for the elicitation of vasosensory reflex responses altering CVR parameters.

Results: Instillation (i.a.) of bradykinin produced immediate (5–8 s) hypotensive (40% of initial), bradycardiac (17% of initial), tachypnoeic (45% of initial), and hyperventilatory (96% of initial) responses. In the vagotomized rats, bradykinin-induced hypotensive (18% of initial), bradycardiac (1% of initial), tachypnoeic (5% of initial), and hyperventilatory (10% of initial) responses attenuated significantly.

Conclusion: Pre-treatment with bilateral vagotomy significantly attenuated the mean arterial pressure, heart rate, respiratory frequency and respiratory minute volume responses indicating the role of vagus in producing these responses.

Key words: Nociception; Vasosensory Reflexes; Bradykinin; Vanilloid Receptor 1; Cardiorespiratory Changes