The influence of chronic sympathectomy on cutaneous blood flow in the rat tail

Tail blood flow (TBF) in the rat markedly increases during sympathetic with drawal such as hyperthermia or lumbar sympathetic blockade. However, a long -term alteration of TBF after chronic sympathetic denervation is not well u nderstood. In the present study, TBF following lumbar sympathectomy (LSX) w as observed to ascertain whether subsequent changes in TBF occur in the abs ence of the sympathetic nervous activity in the rat tail. Assessed by recor ding tail and rectal temperature, the LSX immediately caused an increase in TBF. TBF was gradually decreased along with time and returned to the sham operated (SO) control level within 4 days. About a week after the surgery, a rapid increase in TBF in response to whole body heating was almost abolis hed in denervated animals. Neither hexamethonium (20 mg/kg, i.v.) for gangl ion blockade nor intra-arterial infusion of alpha-receptor antagonist, phen tolamine (10, 100 mu g) produced vasodilation in LSX animals. Nitroprusside , a donor of nitric oxide, produced an increase in TBF in both LSX and SO a nimals. These results indicate that the tail vasculature after LSX constric ts with capability to be vasodilated independent of sympathetic reinnervati on. Quantification of the tail vascular mRNA expression by reverse transcri ptase-polymerase chain reaction showed less endothelial nitric oxide synthe tase in LSX group than that in SO group whereas endothelin-1 was not signif icantly different in both groups. It is suggested that functional changes i n tail vascular endothelium takes at least a part in the reduction in TBF a fter LSX.