Changes in midline thalamic recruiting responses in the prefrontal cortex of the rat during the development of chronic limbic seizures

• Published in: Epilepsia (Copenhagen) 2009-03, Vol.50 (3), p.556-565
• Main Authors: Sloan, David M., Bertram III, Edward H.
• Format: Article
• Language: English
• Subjects: Animals; Biological and medical sciences; Cell Death - physiology; Electroencephalography; Epilepsy, Temporal Lobe - pathology; Epilepsy, Temporal Lobe - physiopathology; Evoked Potentials - physiology; Headache. Facial pains. Syncopes. Epilepsia. Intracranial hypertension. Brain oedema. Cerebral palsy; Investigative techniques, diagnostic techniques (general aspects); Kindling, Neurologic - physiology; Limbic System - pathology; Limbic System - physiopathology; Medical sciences; Mediodorsal nucleus; Mediodorsal Thalamic Nucleus - pathology; Mediodorsal Thalamic Nucleus - physiopathology; Midline Thalamic Nuclei - pathology; Midline Thalamic Nuclei - physiopathology; Nerve Net - pathology; Nerve Net - physiopathology; Nervous system; Nervous system (semeiology, syndromes); Neurology; Prefrontal cortex; Prefrontal Cortex - pathology; Prefrontal Cortex - physiopathology; Radiodiagnosis. Nmr imagery. Nmr spectrometry; Rats; Reaction Time - physiology; Recruiting response; Recruitment, Neurophysiological - physiology; Reuniens; Signal Processing, Computer-Assisted; Status Epilepticus - pathology; Status Epilepticus - physiopathology; Temporal lobe epilepsy
• ISSN: 0013-9580; 1528-1167
• DOI: 10.1111/j.1528-1167.2008.01790.x

Summary Purpose:  Mesial temporal lobe epilepsy (MTLE) is a common form of epilepsy that affects the limbic system and is associated with decreases in memory and cognitive performance. The medial prefrontal cortex (PC) in rats, which has a role in memory, is associated with and linked anatomically to the limbic system, but it is unknown if and how MTLE affects the PC. Methods:  We evoked responses in vivo in the PC by electrical stimulation of the mediodorsal (MD) and reuniens (RE) nuclei of the thalamus at several time points following status epilepticus, before and after onset of spontaneous seizures. Kindled animals were used as additional controls for the effect of seizures that were independent of epilepsy. Results:  Epileptic animals had decreased response amplitudes and significantly reduced recruiting compared to controls, whereas kindled animals showed an increase in both measures. These changes were not associated with neuronal loss in the PC, although there was significant loss in both the MD and RE in the epileptic animals. Conclusions:  There is a significant reduction in the thalamically induced evoked responses in the PCs of epileptic animals. This finding suggests that physiologic dysfunction in MTLE extends beyond primary limbic circuits into areas without overt neuronal injury.