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Targeted hippocampal GABA neuron ablation produces hippocampal sclerosis, epilepsy, and dissociable effects on the Morris water maze and object-place paired association tasks

Targeted hippocampal GABA neuron ablation produces hippocampal sclerosis, epilepsy, and dissociable effects on the Morris water maze and object-place paired association tasks

Truckenbrod LM, Bumanglag AV, Chun E, Hernandez A, Federico QP, Maurer AP, Sloviter RS, Burke SN (2019) Targeted hippocampal GABA neuron ablation produces hippocampal sclerosis, epilepsy, and dissociable effects on the Morris water maze and object-place paired association tasks. Neuroscience 2019 Abstracts 158.03. Society for Neuroscience, Chicago, IL.

Summary: An epileptogenic role for hippocampal GABAergic dysfunction has recently been reported (Chun et al. 2019). Specifically, selective ablation of hippocampal GABA neurons by Stable Substance P-saporin (SSP-saporin) conjugate caused dorsal hippocampal sclerosis and chronic epilepsy, without involving convulsive status epilepticus or widespread brain injury. The current study assessed cognitive function in chronically epileptic SSP-saporin-treated rats and their vehicle-injected controls ~8 months following injection. First, rats completed the Morris Water Maze test of spatial learning and memory (Morris et al., 1982). Animals then underwent testing with the object-place paired association (OPPA) task, which requires the hippocampus as well as functional connectivity between the hippocampus and cortical areas (Jo and Lee, 2010; Hernandez et al., 2017), and then a simple object discrimination task. Interestingly, both controls and rats with dorsal hippocampal sclerosis and chronic epilepsy were able to learn the location of the hidden platform in the Morris Water Maze task and could also acquire a simple pair-wise object discrimination. However, epileptic rats with dorsal hippocampal sclerosis were significantly impaired on the OPPA task, which requires animals to integrate spatial location memory with a correct object choice and is a more sensitive measure of cognitive dysfunction (Hernandez et al., 2015). These data indicate that, similar to humans with medial temporal lobe epilepsy, selective hippocampal sclerosis and epilepsy in this model do not result in global cognitive decline. Rather, cognitive functions that require functional connectivity between the hippocampus and cortical areas are selectively affected.