Morphologic Changes in Dendrites by Hypoxic Insult and the Influence of Hypothermia in Rats

Abstract

We studied the morphologic changes of dendrites in the rat brain resulting from hypoxic insult and investigated changes under conditions of hypothermia induced before or after hypoxic insult. Hypoxic damage after 3 to 5 minutes of apnea was manifested as morphologic changes in cell bodies in a delayed fashion and in dendrites immediately after restoration of breathing. We believe that these morphologic changes at such an early stage result in synaptic dysfunction and explain the poor neurologic recovery in patients resuscitated after cardiopulmonary arrest. Several basic and clinical studies have found that hypothermia during brain resuscitation protects neurologic function and improves clinical outcome. In the present study, cooling at 34°C decreased pathologic changes in basal dendrites of the cortex but such morphologic effects were not evident in apical dendrites of the cortex. Cooling also lessened degenerative change in the hippocampus at 6 days compared with that within 48 hours after the insult. However, whether cooling delays or protects against pathologic changes after hypoxic damage remains controversial. Furthermore, the effect of hypothermia on synaptic disconnection must be reexamined because dendritec changes first appeared just after insult despite the finding that hypothermia before insult protects against chronic morphologic changes in dendrites.