Introduction: The lateral nucleus serves as the main sensory input of the amygdala and is well known for its involvement in the feed forward and feedback inhibitory role in generation of epileptic foci in pharmacoresistant temporal lobe epilepsy (TLE) patients.

Methods: The NPY neurones being among the most abundant immunoreactive neurones in the region were studied at both a light and electron microscopic level. This is a single blind study amongst a population of patients who have undergone amygdalo-hippocampectomy for recalcitrant seizures not amenable to antiepileptic medication. This quantitative study is amongst two groups, Ammon’s horn (AHS) and non-AHS group, looking at the excitatory and inhibitory driving forces acting on NPY neurons in the human epileptic amygdala. The immunostained amygdala was sectioned utilising an ultramicrotome to obtain both semi- and ultrathin sections for both light and electron microscopic analysis.

Results: In a previous study projection neurones in the amygdala were investigated: on average every 2nd to 10th cross section of a projection neuron had only one Type 2 inhibitory axo-somatic synapse on an ultrathin section (Yilmazer-Hanke et al. 2007 Exp Brain Res. 177:384–399). However the analysis of NPY neurones showed that most neurones had 1-3 axo-somatic synapses per neuronal cross section, many of which were excitatory Type 1 synapses, although Type 2 synapses were also found. Preliminary analyses also suggest that NPY neurons have less perisomatic gliosis than projection neurons.

Conclusions: It was clearly noted that the NPY-ir interneurones neurons have both Type 1 & 2 axo-somatic synapses as compared to a previous recent study revealing that axo-somatic synapses on projection neurones in the lateral amygdala were only Type 2 synapses.

Patient Care: Activation of Y2 and/or Y5 receptors and blockade of Y1 receptors in the central nervous system suppresses seizures in a variety of animal seizure models. (Meurs et. Al, Sept.07) Orally available, brain penetrating Y2 and/or Y5 agonists, and possibly Y1 antagonists, may therefore constitute a novel class of antiepileptic drugs, which could greatly benefit patients with medically refractory epilepsy. This study sheds more light on the available synaptic input on NPY neurones on pharmacoresistant Epilepsy patients.

Learning Objectives: Results so far show that damage of the amygdala in TLE reveal local alterations in the inhibitory circuitries that may contribute to a lower seizure threshold and greater excitability within the amgdala.

References: Yilmazer-Hanke DM, Faber-Zuschratter H, Blümcke I, Bickel M, Becker A, Mawrin C, Schramm J (2007) Axo-somatic inhibition of projection neurons in the lateral nucleus of amygdala in human temporal lobe epilepsy: An ultrastructural study. Exp Brain Res 177: 384-399