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A systematic analysis of the regional water content of the feline nervous system was made. In general, areas rich in grey matter contained about 10-15% more water than white matter areas. Percentage water values were lowest for cranial and peripheral nerves and highest for cerebral cortex, cerebellar cortex, olfactory bulb and other grey matter regions. Values for cerebral cortex varied from about 81.5% for suprasplenic gyrus to over 84% for frontal gyrus. It is suggested that the effective concentrations of dissolved substances in various regions of the nervous system might be influenced greatly by these differences in water content.

The "binding" of 3H-gamma-aminobutyric acid (3H-GABA) and 14C-taurine (7 X 10(-5) M) to synaptosomal fractions of the feline CNS was studied using differential centrifugation and double-isotope methods. Of the regions examined, the "binding" of GABA (in nmole/mg protein) occurred to the greatest extent, in cerebral cortex, olfactory bulb, and colliculi and, to a lesser extent, in caudate nucleus, corona radiata, and fornix. Distribution ratios revealed that GABA binding was greater in the cerebral cortex than in caudate nucleus, brain stem, spinal cord, and white matter regions. The binding of taurine (in nmole/mg protein) was lowest in cerebral cortex and highest in brain stem and spinal gray regions. Distribution ratios for taurine indicated that its accumulation was similar in all CNS regions studied, except for slightly higher values for cerebellar cortex and fornix. These results indicated that preferential binding of both GABA and taurine exists among regions of the feline CNS.

Regional cerebral blood flow (rCBF) was measured with a 32-detector device in patients with severe injury to the central nervous system. Most suffered head injiries in traffic accidents. Many patients were severely demented. Several were comatose or in a so-called persistent vegetative state. Flow was measured at rest and during various forms of stimulation. The resting values were on the whole markedly reduced. The flow patterns often showed distinct correlations with the original brain injury. In the best preserved patients, mental activation caused increases in flow with a normal or near-normal distribution. Cutaneous electric stimulation gave rise to increases in cortical flow even in highly reduced patients with severe brain damage. Patients with total or less than total loss of telencephalic structures with retained brainstem reflexes and respiration ('apallic' patients) did not show any changes in flow on sensory stimulation. We conclude that the technique for measuring rCBF enables us to assess severe damage to the central nervous system quantitatively and also to estimate whether higher functions are retained in severely reduced patients in coma, stupor and apallic state--patients who more or less completely lack behavioural responses.