Abstract: Our previous studies have demonstrated that CGRP could attenuate the effects of ET on blood vessels, regional cerebral blood flow and heart. This contribution of CGRP resulted from a most potent dilation of blood vessels. In this research, rats were administrated ET 10μl into the spinal subarachnoid space at lumbar-sacral region. Some rats were monitored BP, heart rate and the contents of plasma ANP and AVP were determined. The rat appeared variably paraplegic a few minutes after giving ET. When the ET dose was over 40ng, they had a high mortality. When no more than 30ng was administrated, the mortality of rat was 20%. Among survivors, 98% had reversible paraplegia, 25min after CGRP administration, a significantd egree of recovery of paraplegia recovered. Pathological examination 4h after onset of paraplegia showed serious ischemia of spinal cord. It indicates the hindlimb paraplytic effect of ET is probably due to potent constriction of blood vessels. We also observed a few increase of BP and heart rate in the rats I. T. injected ET, but no change after i. v. administration of the same dose of ET. It suggests that the pressor to I. T. ET did not resulted from I. T. ET to peripheral blood flow, it is possible to be induced by the neuronal reflex of I. T. injection of ET.

Key words: intrathecal (I. T.) injection, endothelin (ET), hindlimb paralytic effect, CGRP