title: Difference in vasopressin-induced contraction of basilar arteries from stroke-prone spontaneously-hypertensive rats (SP-SHR) and control Wistar-Kyoto rats (WKY).
abstract: Vasopressin (0.01-0.3 IU/ml) contracted isolated segments of rat basilar arteries from stroke-prone SHR (SP-SHR) and normotensive Wistar-Kyoto rats (WKY) unequally. Basilar arteries from SP-SHR were more responsive to vasopressin than were those from WKY when adrenergic nerve endings were present in both preparations. After destruction of adrenergic nerve endings by in vitro 6-hydroxydopamine treatment, the ED50 for vasopressin in both WKY and SP-SHR arteries decreased by a factor of three, indicating that the contractions caused by vasopressin were similarly modulated by prejunctional neurotransmitter release. However, only arteries from WKY showed prominent rhythmic relaxation-contraction cycles superimposed upon the vasopressin-induced tone. The tension cycles were 20-100 dyn in amplitude and occurred at 1-3 cycles/min. These tension oscillations of WKY were pronounced and obvious, sometimes amounting to as much tension as the underlying tonic contraction. Tension cycles could reflect a physiological contraction-relaxation phasing mechanism that fails to occur in basilar arteries of SP-SHR. The rhythmic activity was enhanced by K+-free solution and abolished by 30 mM K+ solution, suggesting that pacemaker changes in K+ conductance may underlie the WKY tension oscillations. It is suggested that the absence of rhythmic contractions in SP-SHR basilar arteries may be explained by greater activity of the electrogenic Na+-pump, which would tend to prevent the rhythmic oscillations in tension. These observations suggest that vasopressin has a differential action on basilar arteries of SP-SHR and WKY.
mesh_terms: D000320:Adrenergic Fibers / Q000187:drug effects; D000818:Animals; D001488:Basilar Artery / Q000187:drug effects* / Q000294:innervation; D004305:Dose-Response Relationship, Drug; D005260:Female; D006892:Hydroxydopamines / Q000494:pharmacology; D008236:Lypressin / Q000494:pharmacology*; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects*; D016627:Oxidopamine; D051381:Rats; D011918:Rats, Inbred SHR / Q000502:physiology*; D011919:Rats, Inbred Strains / Q000502:physiology*; D011921:Rats, Inbred WKY / Q000502:physiology*
chemical_list: D006892:Hydroxydopamines; D008236:Lypressin; D016627:Oxidopamine