ELECTRICAL-CONDUCTION WITHIN THE CEREBROVASCULATURE OF STROKE-PRONE SPONTANEOUSLY HYPERTENSIVE RATS

Alterations in electrical conductivity between smooth muscle cells (SM Cs) can alter the spread and effectiveness of electromechanical SMC co ntraction. We attempted to determine whether alterations in pressure-d ependent constriction (PDC) occurring in relation to stroke developmen t within the middle cerebral arteries (MCAs) of Wistar-Kyoto stroke-pr one hypertensive rats (SHRsp) were associated with changes in electric al conductivity between the SMCs. Current was injected into nonpressur ized MCAs, using a suction electrode. The conducting distance along th e length of the MCA where the amplitude of the membrane potential defl ection (electrotonic potential) produced by current injection declined to 1/e (length constant) was used to measure conductivity. PDC to a 1 00 mmHg pressure step was measured with a pressure myograph. A loss of PDC in the MCAs of SHRsp preceded stroke development. Heptanol (4 mM) , a gap junction communication inhibitor, reversibly inhibited conduct ivity and PDC in the MCA of prestroke SHRsp. The ability of heptanol t o reversibly inhibit PDC was Likely not related to it's ability to alt er electrical conduction. The length constant of electrical conduction in the MCAs was about 0.75 mm and didn't differ between MCA sampled f rom pre-versus post-stroke SHRsp or Sprague-Dawley rats. It was conclu ded that alterations in electrical conductivity along the MCA could mo dify the spread of PDC, but such changes do not contribute to the loss of PDC within the MCA of poststroke SHRsp.