STRUCTURAL BASIS OF INFORMATION CAPACITY CHANGES OF SENSORY-MOTOR CEREBRAL-CORTEX OF RAT-BRAIN DURING POSTRESUSCITATION PERIOD

In a rat model of asphyxial cardiac arrest the volume of the sensory-m otor cortex and the number of neurons and synapses were determined 90 min, 6 h, and 1, 3, 7, 14, and 30 days post-resuscitation. The number of synapses was determined from serial fragmental sections, using sele ctive contrast in ethanol solution of phosphorotungsten acid (PTA), an d by cytoarchitectonic analysis on medium-thick sections. The sensory- motor cortex (SMC) volume did not change significantly during the subs equent 30 days after resuscitation. The number of neurons decreased fr om (2.462 +/- 0.082) x 10(6) pre-insult to (1.441 +/- 0.098) x 10(6) 3 0 days after resuscitation. Damage was most severe in the small neuron al cell complexes of layers III-IV, which serve as an afferent cortica l 'entrance'. Damage was least in the large neuronal cell complexes of layer V, which serves as an efferent cortical 'outlet'. The number of SMC synapses decreased from (5.920 +/- 0.51) x 10(9) pre-insult to (3 .441 +/- 0.305) x 10(9) 30 days after resuscitation. Damage was most s evere in the synaptic pool of the cortical SMC 'entrance'. An increase in the number of high-efficiency hypertrophic synaptic contacts was o bserved during the post-resuscitation period, which may significantly change interneuronal relationships.