Cyclic Amp and Tissues of the Brain

Abstract

This contribution concerns tissues prepared from the mammalian brain, with minimal damage to cell-structure. Such tissues constitute the simplest level at which the multiplicity of control mechanisms which operate between the cells of neural systems, are exhibited directly: That is, without a transformation of category. A major method of exhibiting control mechanisms is to cause a system to alter its level of activity. In the brain this can readily be caused by some form of excitation. Impinging on a portion of cerebral tissue in situ are two types of input to which the tissue reacts; (i) electrical, by the ion movements of the nerve impulse; and (ii) humoral, from adjacent cells or more distant parts of the body but arriving finally as a chemical substance and by diffusion. Input of each of these types can be brought to bear on the isolated tissue, by electrical stimulation and by chemical additions to the fluid environment of the tissue. This is the order in which responses by the tissue are now to be described.