Different states of synaptic vesicle priming explain target cell type-dependent differences in neurotransmitter release.

Autor: Aldahabi M; Laboratory of Cellular Neurophysiology, Hungarian Research Network Institute of Experimental Medicine, Budapest 1083, Hungary.; János Szentágothai School of Neurosciences, Semmelweis University, Budapest 1085, Hungary., Neher E; Laboratory of Membrane Biophysics, Max Planck Institute for Multidisciplinary Sciences, 37077 Göttingen, Germany., Nusser Z; Laboratory of Cellular Neurophysiology, Hungarian Research Network Institute of Experimental Medicine, Budapest 1083, Hungary.
Jazyk: angličtina
Zdroj: Proceedings of the National Academy of Sciences of the United States of America [Proc Natl Acad Sci U S A] 2024 Apr 30; Vol. 121 (18), pp. e2322550121. Date of Electronic Publication: 2024 Apr 24.
DOI: 10.1073/pnas.2322550121
Abstrakt: Pronounced differences in neurotransmitter release from a given presynaptic neuron, depending on the synaptic target, are among the most intriguing features of cortical networks. Hippocampal pyramidal cells (PCs) release glutamate with low probability to somatostatin expressing oriens-lacunosum-moleculare (O-LM) interneurons (INs), and the postsynaptic responses show robust short-term facilitation, whereas the release from the same presynaptic axons onto fast-spiking INs (FSINs) is ~10-fold higher and the excitatory postsynaptic currents (EPSCs) display depression. The mechanisms underlying these vastly different synaptic behaviors have not been conclusively identified. Here, we applied a combined functional, pharmacological, and modeling approach to address whether the main difference lies in the action potential-evoked fusion or else in upstream priming processes of synaptic vesicles (SVs). A sequential two-step SV priming model was fitted to the peak amplitudes of unitary EPSCs recorded in response to complex trains of presynaptic stimuli in acute hippocampal slices of adult mice. At PC-FSIN connections, the fusion probability (P fusion ) of well-primed SVs is 0.6, and 44% of docked SVs are in a fusion-competent state. At PC-O-LM synapses, P fusion is only 40% lower (0.36), whereas the fraction of well-primed SVs is 6.5-fold smaller. Pharmacological enhancement of fusion by 4-AP and priming by PDBU was recaptured by the model with a selective increase of P fusion and the fraction of well-primed SVs, respectively. Our results demonstrate that the low fidelity of transmission at PC-O-LM synapses can be explained by a low occupancy of the release sites by well-primed SVs.
Competing Interests: Competing interests statement:The authors declare no competing interest.
Databáze: MEDLINE
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