During the coming year (1974) work on this project will include the following: 1. Completion of a detailed study of the locations, fine structural details and sources of the synaptic vesicles containing dense cores that are in or near the substantia gelatinosa of the spinal cord. The study will use cats, dogs and monkeys and include normal animal animals, animals subjected to dorsal root resections and to double hemisection of the spinal cord. 2. Attempts will be made to determine the active ingredients of the dense cores and especially to establish whether or not they contain biologically active amines. 3. Tests will be made to determine the feasibility of obtaining samples of astrocyte mitochondria without cristae from the dorsolateral region of cat spinal cord. 4. A study of specialized cell junctions between astrocytes and neural elements will be initiated.