Threshold of seizure activity of the brain and higher nervous activity in the postresuscitation period for intracerebral allotransplantation of fetal neocortex tissue

Abstract

The threshold of seizure activity of the brain, long-term memory, and learning ability are studied in Wistar rats for bilateral transplantation of fetal nervous tissue in area CA1 of the hippocampus. The grafts are performed on the 2nd, 7th, 14th and 30th days after clinical death caused by asphyxia. A neurotransplantation performed on the 2nd day of the postresuscitation period is found to prevent seizure activity, whereas that performed on the 7th-14th days results in a sharp decline or cessation of spontaneous and induced epileptiform convulsive seizures, prolonged preservation of the long-term memory trace, an improvement of learning ability, and a lessening of defensive and phobic behavior in a large proportion of the animals. Key Words: seizure activity; higher nervous activity; postresuscitation oeriod; fetal nervous tissue transplantationThe homeostatic control mechanisms regulating the seizure readiness of the brain are known to fail after clinical death (CD), resulting in spontaneous convulsive seizures and enhanced sensitivity to the epileptogenic effect of different stimuli, as well as a lowering of the threshold of brain seizure activity (TBSA) and disturbances of long-term memory [9,11]. Other sequelae in the postresuscitation period are disturbances of the cerebral microcirculation and metabolic processes, a reduction in the density of neurons and synapses, reorganization of the synaptoarchitectonics, and a shrinking of the receptive area of neurons in the neocortex, hippocampus, amygdaloid complex, and ventrolateral nucleus of the thalamus [8,9]. It is known that transplantation of fetal nervous tissue leads to a TBSA increase, and improvement of higher nervous activity values in rats of the Krushinsky-Molodkina line with a genetically determined high brain seizure readiness and focal lesions of the hippocampus and amygdaloid complex [4,5]. However, the influence of neurotransplantation on TBSA and higher nervous activity for diffuse lesions of the brain in the postresuscitation period after CD has been analyzed insufficiently.The aim of this investigation was to study the effect of intracerebral allotransplantation of fetal neocortex tissue on the TBSA and higher nervous activity on rats after CD. MATERIALS AND METHODSCD was modeled on animals under ether anesthesia by interruption of the systemic blood flow as a result of 6-min mechanical asphyxia [12]. The animals were revived with closed chest massage and artificial pulmonary ventilation.TBSA was determined using dosed sound stimuli (86 dB) in a transparent soundproof chamber 1 day after the procedure and then every 3rd day for 180