Prefrontal neuronal morphology in kindling‐prone (FAST) and kindling‐resistant (SLOW) rats

Abstract

The epileptogenic-prone (FAST) and epileptogenic-resistant (SLOW) rat strains have become a valuable tool for investigating neural plasticity. The strains were generated by breeding the rats that required the fewest amygdala stimulations to elicit a stage-5 convulsive seizure (FAST) and rats requiring the most stimulations (SLOW). Previous studies have shown differences in behavior and amygdala physiology in the two strains.This study examined the dendritic morphology of pyramidal neurons in the brains of adult male and female rats of the two strains. The brains were stained with the Golgi-Cox method and the length and branching from layer III pyramidal cells were measured in parietal cortex (Zilles Par1), medial frontal cortex (Zilles Cg3), and orbitofrontal cortex (Zilles AID) in these two strains of rats. We observed significantly longer dendrites in Cg3 in the FAST group but longer dendrites in the SLOW group in AID and Par1.There was also a sex difference (M > F) in Par1 in both strains. These morphological differences can provide insights into the neurobiological basis of the behavioral differences and suggest that localized changes in the amygdala do not occur independently of changes in other brain regions, and especially prefrontal cortex.

Hyperexcitability: From Normal Fear to Pathological Anxiety and Trauma

“…The contrasts may be due to differences in expression of GABA receptor subunits in the lateral and basal amygdala nuclei in slow and fast kindling rats ( Poulter et al, 1999 ). There are also differences in pyramidal cell morphology in the prefrontal cortex between the two strains, but how this relates to seizure susceptibility and behavioral differences in not known ( Reinhart et al, 2021 ). Behaviorally, slow kindling rats display more fearful behavior in an elevated plus maze, open field if previously shocked, and more freezing in inhibitory avoidance, whereas fast kindling rats are hyperactive, impulsive and have deficits on several cognitive tests ( Mohapel and McIntyre, 1998 ; Gilby and O’Brien, 2013 ).…”