Electrical conduction within the cerebrovasculature of stroke-prone spontaneously hypertensive rats.
Alterations in electrical conductivity between smooth muscle cells (SMCs) can alter the spread and effectiveness of electromechanical SMC contraction. We attempted to determine whether alterations in pressure-dependent constriction (PDC) occurring in relation to stroke development within the middle cerebral arteries (MCAs) of Wistar-Kyoto stroke-prone hypertensive rats (SHRsp) were associated with changes in electrical conductivity between the SMCs. Current was injected into nonpressurized MCAs, using a suction electrode. The conducting distance along the length of the MCA where the amplitude of the membrane potential deflection (electronic potential) produced by current injection declined to 1/e (length constant) was used to measure conductivity. PDC to a 100 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 conductivity and PDC in the MCA of prestroke SHRsp. The ability of heptanol to reversibly inhibit PDC was likely not related to it's ability to alter electrical conduction. The length constant of electrical conduction in the MCAs was about 0.75 mm and didn't differ between MCA sampled from pre-versus post-stroke SHRsp or Sprague-Dawley rats. It was concluded that alterations in electrical conductivity along the MCA could modify the spread of PDC, but such changes do not contribute to the loss of PDC within the MCA of poststroke SHRsp.
Smeda
J S
JS
Division of Basic Medical Sciences, Memorial University of Newfoundland, St. John's, Canada. jsmeda@morgan.ucs.mun.ca
King
S R
SR
D000818:Animals; D002536:Cerebral Arteries / Q000502:physiology*; D002560:Cerebrovascular Circulation; D002561:Cerebrovascular Disorders / Q000503:physiopathology*; D004553:Electric Conductivity; D004594:Electrophysiology; D006973:Hypertension / Q000503:physiopathology*; D008564:Membrane Potentials; D051381:Rats; D011918:Rats, Inbred SHR