Comparative studies on synaptosomes: Applicability of the rapid method for preparing synaptosomes to elasmobranch brain.

A flotation technique for the rapid preparation of synaptosomes, originally developed for invertebrate nervous tissue, has now been successfully applied to that of an elasmobranch fish (Mustelis canis, dogfish). The technique involves submitting the supernatant, obtained after a homogenate has been centrifuged at low speed to remove nuclei and tissue debris to centrifugal fields of intermediate intensity (10(6) g/min), appears to separate well-sealed synaptosomes from those less well sealed as judged by the criteria of osmotic shrinkage, enzyme occlusion, and choline uptake. The sealed synaptosomes do not equilibrate with the 0.8 M sucrose used as the homogenization medium and rise to form a coherent pellicle at the top of the tube. Due to the short (1-1/1/2 hr) preparation time, such synaptosomes may well prove useful in further metabolic studies.