The earliest alterations in rat neurones and astrocytes after anoxia-ischaemia.

Abstract

A combined light and electron microscope study was made of the alterations occurring in the neurones and astrocytes of the neocortex and hippocampus of rats killed immediately after intermittent exposures to nitrogen of 5 and 15 min. Blood flow in the right common carotid artery had previously been interrupted by application of an artery clasp which was removed after the exposure to nitrogen and the animals killed by perfusion-fixation with glutaraldehyde. Microvacuolation (MV), the earliest stage of anoxic-ischaemic neuronal damage, was observed in the ipsilateral neocortex and hippocampus of both groups and ischaemic cell change (ICC) bilaterally in the neocortex of animals exposed for 15 min. Ultrastructural examination showed the microvacuoles to be swollen mitochondria. Slightly dense, mildly distorted, non-vacuolated neurones were also seen in the neocortex and hippocampus. They did not exhibit the ultrastructural changes seen in MV and ICC. Swollen astrocytic processes were sometimes seen around the damaged neurones, more frequently after 15 min exposure. Slight swelling of perivascular astrocytic processes was occasionally observed while the extracullular spaces in the neuropil remained unaltered. This implies that the accumulation of fluid in oedematous grey matter is confined to the astrocytic compartment. The reversibility or otherwise of all the neuronal alterations is discussed.