Question: 

The amygdala is critical for temporal lobe epilepsy (TLE), as well as for aversive sensations in epileptic patients. The lateral nucleus (LA), main input station of the amygdala, displays some of the most severe pathologies in TLE. Therefore, we thought it timely to establish a structural functional map of the human LA in relation to epileptic activity.

Methods: 

Slices were obtained from amygdalar tissue (n=11) resected for treatment of pharmacoresistant TLE. Prior to surgery, scalp EEG recordings and MRI were performed. In 3 cases, the electroamygdalogram (EAG) was recorded intraoperatively. Extracellular recordings were performed in all resected slices. After recording, slices were processed for anatomical identification and receptor autoradiography. Experiments were approved by the local ethics committee and informed consent was obtained from all patients.

Results: 

Frequency analysis of EAGs and field potential recordings showed oscillations in the theta domain along with spontaneous epileptiform activity. Spontaneous activity occurred simultaneously at multiple spots in vitro and displayed characteristic differences in spread, suggesting specific sites of origin and pathways. This activity was blocked by application of CNQX (10mM) and bicuculline (10mM), and a rebound occurred after bicuculline washout. In keeping with this, receptor autoradiographic analysis demonstrated specific regional differences in receptor distribution in the LA. For instance, while AMPA, kainate and mGluR2/3 receptor concentration was increased in epileptic slices, that of GABA_A receptor was decreased in epileptic slices as compared to autoptic controls.

Conclusion: 

We were able to demonstrate spontaneous epileptiform activity in the human LA in anatomically identified slices and that it is linked to glutamatergic and GABA_A receptors activity and concentration. We also show that this activity is reflected in vivo, with respect to the occurrence of events as well as to the frequency of the oscillations.