A comparative study of EM fixation procedures for the adult rat spinal cord based on regional blood flow

Adult rat spinal cords were perfused intracardially with aldehyde fixatives containing either sodium cacodylate or sodium phosphate buffer for EM studies. The perfusion flow rate of 24 cc/min for the first 3 min and 33 cc/min for completion of prefixation was found to be optimal. Ultrastructural examination of the L-1 fasciculus gracili, dorsal and ventral horns demonstrated that the quality of fixation is similar despite a two- to three-fold greater blood flow rate to the dorsal and ventral horns, respectively. Sodium cacodylate buffered perfusate provides superior clarity of organelle membranes, myelin lamellae and axoplasmic constituents when compared with sodium phosphate buffer.