Vasoconstriction Induced by ƒÀ-Adrenergic Antagonist in the Tail of Chronic Spinal Rats

Abstract: Adult Wistar male rats were used for this experiment. Spinal cord was transected between the C7 and Th1 vertebrae under anesthetic condition. After the surgical operation, rats were reared in a warm room(30•Ž) as chronic spinal rats, and experiment was also performed in a climatic chamber (30•Ž, 60 % r.h.). During the experiment, conscious spinal rats were placed in a small wire-mesh cage. Propranolol hydrochloride (Prop., 8mg/kg; ƒÀ-adrenergic antagonist) was injected intraperitoneally. Rectal temperature (Tre), tail skin temperature (Ttail) and ambient temperature (Ta) were detected by thermistor probes and recorded simultaneously. In some cases, in addition to such parameters mentioned above, heart rate (HR) calculated by electrocardiogram (ECG) and arterial blood pressure (BP) through the femoral catheter were also recorded. As the index of the tail blood flow, the difference (dTtail) between Ttail and Ta was calculated (dTtail=Ttail-Ta). A sustained decrease in dTtail for 50 min was observed after the Prop. injection in Group-A (S<1W; less than 1 week (W) after the spinalization, N=6), Group-B(1W<S<2W, N=10) and Group-C (2W<S, N=6). In Group-A, meandTtail was 1.5•}0.3•Ž before the injection and 0.8•}0.3•Ž (p<0.05) at 30 min after the injection, mean Tre was 36.3•}0.2•Ž before the injection and 36.2•}0.2•Ž (not significant) at 30 min after the injection. In Group-B, meandTtail was 1.3•}0.4•Ž before the injection and 0.2•}0.2•Ž (p<0.01) at 30 mi