Journal of Orthopaedic Reseurch 9266-274 Raven Press, Ltd., New York 0 1991 Orthopaedic Research Society
The Effect of Acute Denervation on the Microcirculation of Skeletal Muscle: Rat Cremaster Model Long-En Chen, Anthony V. Seaber, *Edward Bossen, and James R. Urbaniak Orthopaedic Research Laboratories, Department of Surgery and ‘Department of Pathology, Duke University Medical Center, Durham, North Carolina, U . S . A .
Summary: Although tissue is denervated during replantation of a severed part, tissue transfer, or muscle transplantation, there are few studies concerning the effects of acute denervation on muscle microcirculation. We have described a surgical procedure that totally denervates the rat cremaster muscle. Histological examination of the denervated tissue has given convincing evidence of nerve degeneration and skeletal muscle atrophy, accompanied by electrophysiological evidence of total denervation. The diameters of each component of the microcirculation were measured before and after denervation. Arterioles and arteries ranging in size from 10 to 70 pm in diameter were found to increase significantly in size immediately after acute denervation. Larger arteries and veins did not undergo significant diametrical increases. These findings suggest that total acute denervation significantly increases the diameter of small arteries and arterioles, thereby decreasing the resistance in the arterial bed and increasing blood flow. Since this phenomenon is of limited duration (20 min), it would appear to be ineffective in enhancing reperfusion and oxygenation at the time of reattachment of amputated parts or during vascularized tissue transfers, until methods of prolonging it for several hours or more are found. Key Words: Skeletal muscle-Denervation-Rat cremaster.
Since Grant first introduced the procedure of incising the scrotum and exposing the anterior aspect of a rat’s cremaster in 1964 (9), this muscle has been widely used to study the effects of various drugs (5,6,19), hemorrhagic shock (25), ischemia (13), and vasospasm (22). There has been some difficulty in acquiring satisfactory denervation in the rat cremaster model because of the muscle’s multiple fine nerve and vessel supply. Grant used a flank incision from the scrotum to the diaphragm to cut all the nerves proximally, including the sympathetic nerve under the diaphragm (10). Although denervation can be generated in this manner, this model is not as convenient for studying acute denervation o r long-term ischemia because of the severe operative injury involved. Anderson and colleagues (1) recently re-
In 1966 Grant observed the phenomenon of vasodilation after acute denervation in the rat cremaster muscle, but no measurements were taken (10). Midrio described a transient two- to threefold increase in blood flow of the hindleg of the dog after cutting the femoral nerve or the sciatic nerve, an increase that returned to control level within 5-20 min (20). Weiss used alpha blockage to cause a
The Effect of Acute Denervation on the Microcirculation of Skeletal Muscle: Rat Cremaster Model Long-En Chen, Anthony V. Seaber, *Edward Bossen, and James R. Urbaniak Orthopaedic Research Laboratories, Department of Surgery and ‘Department of Pathology, Duke University Medical Center, Durham, North Carolina, U . S . A .
Summary: Although tissue is denervated during replantation of a severed part, tissue transfer, or muscle transplantation, there are few studies concerning the effects of acute denervation on muscle microcirculation. We have described a surgical procedure that totally denervates the rat cremaster muscle. Histological examination of the denervated tissue has given convincing evidence of nerve degeneration and skeletal muscle atrophy, accompanied by electrophysiological evidence of total denervation. The diameters of each component of the microcirculation were measured before and after denervation. Arterioles and arteries ranging in size from 10 to 70 pm in diameter were found to increase significantly in size immediately after acute denervation. Larger arteries and veins did not undergo significant diametrical increases. These findings suggest that total acute denervation significantly increases the diameter of small arteries and arterioles, thereby decreasing the resistance in the arterial bed and increasing blood flow. Since this phenomenon is of limited duration (20 min), it would appear to be ineffective in enhancing reperfusion and oxygenation at the time of reattachment of amputated parts or during vascularized tissue transfers, until methods of prolonging it for several hours or more are found. Key Words: Skeletal muscle-Denervation-Rat cremaster.
Since Grant first introduced the procedure of incising the scrotum and exposing the anterior aspect of a rat’s cremaster in 1964 (9), this muscle has been widely used to study the effects of various drugs (5,6,19), hemorrhagic shock (25), ischemia (13), and vasospasm (22). There has been some difficulty in acquiring satisfactory denervation in the rat cremaster model because of the muscle’s multiple fine nerve and vessel supply. Grant used a flank incision from the scrotum to the diaphragm to cut all the nerves proximally, including the sympathetic nerve under the diaphragm (10). Although denervation can be generated in this manner, this model is not as convenient for studying acute denervation o r long-term ischemia because of the severe operative injury involved. Anderson and colleagues (1) recently re-
In 1966 Grant observed the phenomenon of vasodilation after acute denervation in the rat cremaster muscle, but no measurements were taken (10). Midrio described a transient two- to threefold increase in blood flow of the hindleg of the dog after cutting the femoral nerve or the sciatic nerve, an increase that returned to control level within 5-20 min (20). Weiss used alpha blockage to cause a
