PRESSOR EFFECT PRODUCED BY STIMULATION OF SOMATIC NERVE ON HEMORRHAGIC HYPOTENSION IN CONSCIOUS RATS
SuN XIANG-YING;YU JUN AND YAO TAI(Department of Physiology,Shanghai First Medical College,Shanghai)
Experiments were carried out on male conscious rats.Hemorrhagic hypo-tension was produced by withdrawing blood 50% of the total blood volume)fromthe venous catheter.The animals were divided into two groups.In controlgroup,no treatment was given following hemorrhage.One hour after bleeding,the mean arterial pressure was maintained at a low level of 66% of the control value.In stimulation group,the sciatic nerve was stimulated with low frequency elec-trical pulses.The stimulation was lasted for 30 min.During stimulation,themean arterial pressure was 81% of the control level.The splanchnic nerve dis-charge was also increased.After the cessation of sciatic stimulation,the meanarterial pressure level was still significantly higher than that of the control group.This pressor response upon sciatic nerve stimulation was neither reversed norprevented by naloxone(8 mg/kg,i.v.).In chloral hydrate(400 mg/kg,i.p.)anaesthetized rats,stimulation of the sciatic nerve during hemorrhagic hypotensionstill produced an increase in arterial pressure.However,the pressor response wassignificantly decreased or even abolished by pretreatment of scopolamine(8 mg/kg,i.v.).The results obtained indicate that stimulation of the somatic nerve in animalswith hemorrhagic hypotension can further enhance the sympathetic activity andthus facilitate the recovery of blood pressure.The mechanism underlying thesomatic stimulation-induced pressor response in hypotensive animals is discussed.