Morphological Changes and Characteristics of the Expression of Serine Racemase in the Rat Hippocampus in Combined Stress

Abstract

Structural changes in the ventral segment of the hippocampus and the characteristics of the expression of serine racemase were studied in rats aged 12 and 24 months exposed to combined stress. Four groups of 10 animals were formed: group 1 were control rats aged 12 months; group 2 were control rats aged 24 months; group 3 were 12-month rats subjected to 30-min stress daily for seven days; group 4 were 24-month rats subjected to stress. Stress was applied in a special apparatus consisting of six isolated sectors of identical volume and allowing the combination of different types of stress to be applied (pulsing light, loud noise, vibration). The ventral segment of the hippocampus of experimental animals showed an increase in the specific number of shrunken hyperchromic neurons in field CA3 and decreases in neuron density, accompanied by pericellular edema, cytoplasmic vacuolization, and decreased serine racemase expression in the neuropil of the radial layer of fields CA1 and CA3. Stressed animals showed changes in neurons in the pyramidal layer of field CA3, which were combined with a decrease in the level of expression of serine racemase in dendrites in the radial layer of fields CA1 and CA3, which is taken as a sign of impairment to NMDA receptor-mediated transmission of nerve spikes in the hippocampus.