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Synaptic heterogeneity between mouse paracapsular intercalated neurons of the amygdala
Article first published online: 14 NOV 2007
©2007 The Authors. Journal compilation © 2007 The Physiological Society
The Journal of Physiology
Volume 585, Issue 1, pages 117–134, November 2007
How to Cite
Geracitano, R., Kaufmann, W. A., Szabo, G., Ferraguti, F. and Capogna, M. (2007), Synaptic heterogeneity between mouse paracapsular intercalated neurons of the amygdala. The Journal of Physiology, 585: 117–134. doi: 10.1113/jphysiol.2007.142570
- Issue published online: 14 NOV 2007
- Article first published online: 14 NOV 2007
- (Received 6 August 2007; accepted after revision 1 October 2007; first published online 4 October 2007)
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 GABAB 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.