Background: Since long back, it has been a matter of discussion regarding the role of
peripheral blood vessels in the regulation of cardiorespiratory (CVR) system.
Objective: The role of 5-HT3 and TRPV1 receptors present on perivascular nerves in elicitation of
CVR reflexes was examined after intra-arterial instillation of bradykinin in urethane anesthetized
Materials and Methods: Femoral artery was cannulated retrogradely and was utilized for the instillation
of saline/agonist/antagonist and recording of blood pressure (BP), using a double ported 24G
cannula. BP, respiration and ECG were recorded for 30 min after bradykinin (1 μM) in the absence
or presence of antagonists.
Results: Instillation of bradykinin produced immediate hypotensive (40%), bradycardiac (17%),
tachypnoeic (45%) and hyperventilatory (96%) responses of shorter latencies (5-8 s) favoring the
neural mechanisms in producing the responses. In lignocaine (2%) pretreated animals, bradykinin-
induced hypotensive (10%), bradycardiac (1.7%), tachypnoeic (13%) and hyperventilatory
(13%) responses attenuated significantly. Pretreatment with ondansetron (100 μg/kg), 5-HT3-antagonist
attenuated the hypotensive (10%), bradycardiac (1.7%), tachypnoeic (11%) and hyperventilatory
(11%) responses significantly. Pretreatment with capsazepine (1 mg/kg), transient receptor potential
vanilloid 1- antagonist blocked the hypotensive (5%), bradycardiac (1.2%), tachypnoeic
(6%) and hyperventilatory (6%) responses significantly.
Conclusion: In conclusion, presence of a nociceptive agent in the local segment of an artery
evokes vasosensory reflex responses modulating CVR parameters involving TRPV1 and 5-HT3 receptors
present on the perivascular sensory nerve terminals in anesthetized rats.