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This Article Full Text Full Text (PDF) Supplemental Data All Versions of this Article: 585/1/117    most recent jphysiol.2007.142570v1 Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Geracitano, R. Articles by Capogna, M. Search for Related Content PubMed PubMed Citation Articles by Geracitano, R. Articles by Capogna, M. Related Collections Neuroscience

¹ MRC, Anatomical Neuropharmacology Unit, Oxford OX1 3TH, UK
² Department of Pharmacology, Innsbruck Medical University, A-6020 Innsbruck, Austria
³ Laboratory of Molecular Biology and Genetics, Institute of Experimental Medicine, 1083 Budapest, Hungary

GABAergic medial paracapsular intercalated (Imp) neurons of amygdala are thought of as playing a central role in fear learning and extinction. We report here that the synaptic network formed by these neurons exhibits distinct short-term plastic synaptic responses. The success rate of synaptic events evoked at a frequency range of 0.1–10 Hz varied dramatically between different connected cell pairs. Upon enhancing the frequency of stimulation, the success rate increased, decreased or remained constant, in a similar number of cell pairs. Such synaptic heterogeneity resulted in inhibition of the firing of the postsynaptic neurons with different efficacies. Moreover, we found that the different synaptic weights were mainly determined by diversity in presynaptic release probabilities rather than postsynaptic changes. Sequential paired recording experiments demonstrated that the same presynaptic neuron established the same type of synaptic connections with different postsynaptic neurons, suggesting the absence of target-cell specificity. Conversely, the same postsynaptic neuron was contacted by different types of synaptic connections formed by different presynaptic neurons. A detailed anatomical analysis of the recorded neurons revealed discrete and unexpected peculiarities in the dendritic and axonal patterns of different cell pairs. In contrast, several intrinsic electrophysiological responses were homogeneous among neurons, and synaptic failure counts were not affected by presynaptic cannabinoid 1 or GABA_B receptors. We propose that the heterogeneous functional connectivity of Imp neurons, demonstrated by this study, is required to maintain the stability of firing patterns which is critical for the computational role of the amygdala in fear learning and extinction.

(Received 6 August 2007; accepted after revision 1 October 2007; first published online 4 October 2007)
Corresponding author M. Capogna: MRC Anatomical Neuropharmacology Unit, Mansfield Road, Oxford OX1 3TH, UK. Email: marco.capogna{at}pharm.ox.ac.uk