REDUCED SYMPATHETIC NORADRENERGIC NEUROTRANSMISSION IN THE TAIL ARTERY OF DONRYU RATS FED WITH HIGH CHOLESTEROL-SUPPLEMENTED DIET

1 Sympathetic neurotransmission and noradrenaline content of the tail artery of Donryu rats fed for 2 months with a cholesterol-supplemented diet enriched with 4% cholesterol, 1% cholic acid, 0.5% thiouracil (C CT), were examined. 2 Total serum cholesterol level of CCT fed rats (7 .05+/-1.77 mg ml(-1), n=8 was significantly greater than lab-chow fed controls (2.58+/-0.32 mg ml(-1), n=8). Low density lipoprotein level w as also significantly increased in CCT-fed (1.79+/-0.26 mg ml(-1), n=8 ) compared with control fed rats (1.35+/-0.25 mg ml(-1), n=8) but plas ma levels of triglyceride and high density lipoproteins did not differ significantly between the two groups. 3 Contractile responses of the arterial rings to transmural nerve stimulation (65 V, 0.1 ms, 4-64 Hz. 1 s), were markedly attenuated in the CCT fed animals compared with t he controls. This reduction involved the noradrenergic rather than pur inergic component of sympathetic transmission. 4 Vasoconstrictor respo nses to exogenous noradrenaline (0.01-300 mu M) and adenosine 5'-triph osphate (0.3-1000 mu M) were unaffected by CCT diet, indicating prejun ctional alteration of sympathetic neurotransmission during CCT-induced hyperlipidaemia. 5 The noradrenaline content of the tail arteries of CCT fed animals (2.64+/-0.36 ng mg(-1), n=6) was significantly lower t han that of controls (3.82+/-0.32 ng mg(-1), n=6). 6 These findings sh ow that chronic treatment t of Donryu rats with a cholesterol-suppleme nted diet led to altered levels of circulating lipid fractions accompa nied bg attenuated sympathetic noradrenergic neurotransmission and red uced noradrenaline content of the rat tail artery.