Title - Feature Finding
Featured Finding Figure
Different subclasses of gamma-aminobutyric acid (GABA) cortical neurons can be distinguished by their content of neuropeptides such as somatostatin (SST), or calcium-binding proteins such as calretinin (CR). SST, but not CR, neurons have been reported to be altered in the prefrontal cortex of subjects with schizophrenia. Understanding the functional significance of the SST neuron disturbances in schizophrenia requires knowledge of the specialized synaptic circuitry of these neurons relative to that of CR neurons. Consequently, we used immuno-electron microscopy to examine the synaptic type and postsynaptic targets of SST-immunoreactive (IR) axon terminals in monkey prefrontal cortex and compared these findings with similar data for CR-IR axon terminals. SST-IR axon terminals formed exclusively symmetric synapses and contacted only dendritic shafts (86%) and dendritic spines (14%) (see figure), whereas CR-IR terminals also formed synapses with cell bodies. The postsynaptic targets of SST-IR axon terminals also differed across layers with synapses onto dendritic spines more frequent in the superficial (20%) than in the deep (8%) layers. Dual-label immunoelectron microscopy revealed that CR-IR axon terminals targeted GABA-IR dendritic shafts with a greater frequency (60%) than did SST-IR axon terminals (21.5%). Conversely, SST-IR axon terminals contacted unlabeled dendritic shafts, presumably belonging to pyramidal neurons, more frequently than did CR-IR axon terminals (57% versus 19%, respectively). This specialized synaptic circuitry of SST neurons in the primate prefrontal cortex suggests that the alterations of these neurons in schizophrenia is likely to have distinct functional consequences.
Melchitzky DS and Lewis DA: Dendritic-targeting GABA neurons in monkey prefrontal cortex: Comparison of somatostatin- and calretinin-immunoreactive axon terminals. Synapse 62: 456-465, 2008.

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David A. Lewis, M.D. | Department of Psychiatry | University of Pittsburgh
3811 O'Hara Street, Biomedical Science Tower W1654
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