Bimodal Electrical Properties of Rat Major Artery Segment In Situ

In experiments on narcotized rats, BP in the left femoral artery as well as local electrical potential and electrical impedance of the symmetric segment of the right femoral artery were simultaneously recorded in situ with two extracellular nonpolarizable Ag/AgCl electrodes located along the artery at a distance of 3 mm from each other. The pulsatile arterial electrical potentials with amplitude of 100-200 μV and duration of about 50 msec were recorded, which coincided with the front of BP wave corrected for a 10-msec delay of the pressure transducer. Under normal conditions, the pulsatile oscillations of arterial electroimpedance were in-phase with BP oscillations, so the rising phase of BP was paralleled by elevation of electroimpedance reflecting constriction of the arterial segment. This finding is viewed as indicative of periodic myogenic Ostroumov-Bayliss effect triggered by arterial pulse. After local application of tetrodotoxin (3×10^-7 М), procaine (0.5%), or lidocaine (spray 10%) to isolated arterial segment, its electroimpedance oscillated out-of-phase with BP, so the changes of electroimpedance were similar to the response of a passive elastic tube to pulsatile BP. The applied agents completely (tetrodotoxin) or pronouncedly (procaine, lidocaine) inhibited the pulsatile arterial electrical potential. The present data indicate the possibility of passive and active modes of arterial pulsing, which differ by the amplitude of pulsatile arterial electrical potential as well as by phasic relations between BP and electroimpedance. The possible physiological role of various modes of pulsing in major arteries is discussed.