Retrograde cannulation of femoral artery: A novel experimental design for precise elicitation of vasosensory reflexes in anesthetized rats

Vasosensory reflex responses are elicited by instillation of nociceptive agents in a segment of peripheral blood vessel. A novel method for the stimulation of perivascular afferents was designed by retrograde cannulation of femoral artery, using a 24G, double ported polyethylene cannula. The vertical port of which was used to inject the algogen into the artery and horizontal port to measure the BP continuously, as this port was connected to the pressure transducer. Previously, separate carotid artery cannulation was used for the BP recording. But our experimental design excluded the need for carotid artery cannulation that might compromise the circulation to the CNS centers mediating cardiorespiratory reflex responses. After cannulation, the proximal end of femoral artery became an end artery and the drugs were instilled retrogradely. The volume of chemicals was kept minimal (100 µl) and the ipsilateral femoral vein was also ligated. These measures made sure that the instilled drug remained in a local segment of femoral artery and did not spill out to the systemic circulation. Further, there was no increase in the water content of ipsilateral paw as compared to the contralateral paw. This finding also substantiates our proposition regarding minimal systemic spillage. • The femoral artery is cannulated by a double ported cannula. • This cannula helps instillation of algogen and BP measurement simultaneously. • Retrograde instillation helps to deposit the algogen in a local segment of femoral artery.