Organ Specificity in the responses of isolated arteries to anesthetics.

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The present study attempts to clarify the organ specificity in the responses to anesthetics of isolated arteries of different organs (cerebral, coronary, mesenteric, renal and femoral arteries). (1) In arterial strips under resting tension, the addition of thiamylal and thiopental(10^<-5> to 10^<-3> M) caused a dose-related contraction; the contraction was significantly more intense in cerebral than in extracerebral arteries. Secobarbital and pentobarbital failed to produce a significant contraction. Thiobarbiturates-induced contraction was attenuated by Ca channel blockers and abolished by the removal of Ca^<++> from extracellular fluids.(2) In arterial strips previously contracted with KC1 or prostaglandin F_2alpha (PGF_<>alpha), thiobarbiturates in low concentrations (<10^<-4> M) produced a further contraction and in high concentrations (>3x10^<-4> M) a profound relaxation, indicating that thiobarbiturates possess biphasic effects. By contrast, oxybarbiturates were revealed to possess only relaxing effect.(3) Regional difference of the response to halothane and isoflurane of large (>2.0 mm, OD) and small (<1.0 mm, OD) was investigated. Halothane (1-3 MAC) and nitroglycerin (NTG, 10^<-9> to 10^<-5> m) were revealed to produce greater relaxations in large than in small coronary arteries, and in contrast, isoflxirane (1-3 MAC) and adenosine (10^<-7> to 10^<-4> m) was revealed to produce relaxations greater in small than in large coronary arteries.These findings with isolated arteries from different organ suggest that the vascular effects of anethetics are uniform in different organs. These different effects may contribute to maldistribution of blood flow during anesthesia.