The nature and time course of the neuronal alterations resulting from oligaemia and hypoglycaemia in the brain of Macaca mulatta

(1) The time course of the neuronal alterations known as ‘ischaemic cell change’ has been studied after profound arterial hypotension or insulin-induced hypoglycaemia in the brains of rhesus monkeys fixed by perfusion at intervals of 15 min-4 h after the stress. (2) Arterial hypotension (a cerebral perfusion pressure less than 25 mm Hg for 4–36 min, produced by drugs, bleeding and head-up tilt) led to consistent neuronal alterations in the arterial boundary zones of the neocortex, and less frequent alterations in the hippocampus, basal ganglia and cerebellum. (3) Arterial glucose levels below 20 mg/100 ml (induced by insulin 800–1200 I.U., and sustained so that somatosensory-evoked potentials were abolished for 49–92 min) was followed by ischaemic neuronal alterations occurring diffusely in the neocortex and also in the hippocampus, caudate nucleus and putamen. (4) In the two situations the neuronal changes were identical both in their nature and time course. The earliest change was microvacuolation of the neuronal cytoplasm, visible after + 15 min and persisting up to + 150 min. This was followed by ischaemic cell change, recognizable after + 30–35 min and persisting up to + 4 h. Ischaemic cell change with incrustations appeared after + 90–150 min. (5) This sequence of changes occurred most rapidly in the smaller neocortical neurones, in which the time course was closely similar to that previously described in the rat brain.