The Ability of NMDA-Type Glutamate Receptor Blockers to Prevent the Development of Pentylenetetrazole Kindling and Morphological Changes to Pyramidal Neurons in the Mouse Hippocampus

• Published in: Neuroscience and behavioral physiology 2015-06, Vol.45 (5), p.528-535
• Main Authors: Vasil’ev, D. S., Tumanova, N. L., Lavrent’eva, V. V., Starshinova, L. A., Zhabko, E. P., Lukomskaya, N. Ya, Zhuravin, I. A., Magazanik, L. G.
• Format: Article
• Language: English
• Subjects: Animals; Behavioral Sciences; Biomedical and Life Sciences; Biomedicine; Convulsions & seizures; Morphology; Neurobiology; Neurons; Neurosciences; Physiology
• ISSN: 0097-0549; 1573-899X
• DOI: 10.1007/s11055-015-0106-8

Experiments on mice addressed the link between convulsive syndrome and morphological changes in hippocampal neurons occurring on development of pentylenetetrazole (PTZ) kindling. Kindling was induced by i.p. PTZ (35 mg/kg) three times a week for one month. By the end of this period, 70% of the mice responded to administration of PTZ with severe clonic or clonic-tonic seizures. Hippocampal sections (stratum pyramidale, field CA1, Nissl staining) from convulsive mice showed large numbers of altered cells (24.7 ± 2.1%). Most of these were pyramidal neurons. These hyperchromic neurons had reduced body sizes, loss of turgor, wrinkling of the cell body, and deformation of dendritic processes. These dark-type changes were present in 2.3 ± 2.1% of neurons in the hippocampus of intact mice and mice resistant to the convulsogenic effect of PTZ (30% of the population). Immunohistochemical studies demonstrated normal expression of NeuN (Fox3) protein in all hippocampal cells, including dark hyperchromic neurons. This is evidence that neurons did not die en masse and were relatively viable. Prophylactic s.c. administration of NMDA receptor blockers (0.5 mg/kg memantine, 0.1 mg/kg IEM-1921, or 1 mg/kg IEM-1958) decreased the proportion of mice developing PTZ kindling from 70% to 40%. The proportion of altered neurons in the 60% of mice given NMDA blockers and not developing PTZ kindling or convulsions in the presence of blockers was 0.1 ± 0.06%, which was the same as in intact mice. Conversely, the hippocampus of mice demonstrating convulsions despite simultaneous administration of NMDA blockers showed 24.0 ± 5.6% hyperchromic neurons. These results provide evidence that pathologically altered neurons appeared after convulsive seizures in animals after PTZ kindling and that blockade of NMDA glutamate receptors could weaken both the development of convulsive syndrome and the concomitant morphological changes to hippocampal neurons.