The Journal of Neuroscience, November 4, 2009, 29(44):13883-13897; doi:10.1523/JNEUROSCI.2457-09.2009
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Cellular/Molecular
Neuroligin-2 Deletion Selectively Decreases Inhibitory Synaptic Transmission Originating from Fast-Spiking but Not from Somatostatin-Positive Interneurons
Jay R. Gibson,1
Kimberly M. Huber,1 and
Thomas C. Südhof1,2,3,4
1Department of Neuroscience and 2Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, Texas 75390, and 3Department of Molecular and Cellular Physiology and 4Howard Hughes Medical Institute, Stanford University School of Medicine, Palo Alto, California 94304
Correspondence should be addressed to Jay R. Gibson, Department of Neuroscience, University of Texas Southwestern Medical Center, Box 9111, Dallas, TX 75390-9111. Email: Jay.Gibson{at}UTSouthwestern.edu
Neuroligins are cell adhesion molecules involved in synapse formation and/or function. Neurons express four neuroligins (NL1–NL4), of which NL1 is specific to excitatory and NL2 to inhibitory synapses. Excitatory and inhibitory synapses include numerous subtypes. However, it is unknown whether NL1 performs similar functions in all excitatory and NL2 in all inhibitory synapses, or whether they regulate the formation and/or function of specific subsets of synapses. To address this central question, we performed paired recordings in primary somatosensory cortex of mice lacking NL1 or NL2. Using this system, we examined neocortical microcircuits formed by reciprocal synapses between excitatory neurons and two subtypes of inhibitory interneurons, namely, fast-spiking and somatostatin-positive interneurons. We find that the NL1 deletion had little effect on inhibitory synapses, whereas the NL2 deletion decreased (40–50%) the unitary (cell-to-cell) IPSC amplitude evoked from single fast-spiking interneurons. Strikingly, the NL2 deletion had no effect on IPSC amplitude evoked from single somatostatin-positive inhibitory interneurons. Moreover, the frequency of unitary synaptic connections between individual fast-spiking and somatostatin-positive interneurons and excitatory neurons was unchanged. The decrease in unitary IPSC amplitude originating from fast-spiking interneurons in NL2-deficient mice was due to a multiplicative and uniform downscaling of the amplitude distribution, which in turn was mediated by a decrease in both synaptic quantal amplitude and quantal content, the latter inferred from an increase in the coefficient of variation. Thus, NL2 is not necessary for establishing unitary inhibitory synaptic connections but is selectively required for "scaling up" unitary connections originating from a subset of interneurons.
Received May 26, 2009;
revised Aug. 24, 2009;
accepted Aug. 29, 2009.
Correspondence should be addressed to Jay R. Gibson, Department of Neuroscience, University of Texas Southwestern Medical Center, Box 9111, Dallas, TX 75390-9111. Email: Jay.Gibson{at}UTSouthwestern.edu