76,77 Interestingly, gamma band oscillations in the human DLPFC increase in proportion to working memory load,78 and in subjects with schizophrenia, find more prefrontal gamma band oscillations are reduced bilaterally during a working memory task.79 Thus, a deficit in the synchronization of pyramidal cell firing, resulting from impaired regulation of pyramidal cell networks by PV-positive GABA neurons, may Inhibitors,research,lifescience,medical contribute to reduced levels of induced gamma band oscillations, and consequently to impairments
in cognitive tasks that involve working memory in subjects with schizophrenia.65 Interestingly, CCK/CB1R- and PV-containing cells provide convergent sources of perisomatic inhibition to pyramidal neurons that play specific roles in shaping network activity, including complementary roles in regulating gamma band oscillations.80 Thus, alterations in CCK-containing basket cells could Inhibitors,research,lifescience,medical also contribute to impaired gamma oscillations in schizophrenia. The contribution of developmental plasticity to GABA neuron alterations in schizophrenia In the monkey prefrontal cortex DLPFC, the density of symmetric, presumably GABA, synapses rises rapidly during the third trimester of gestation and perinatal period until stable, adult levels are achieved at 3 months postnatal.36 Inhibitors,research,lifescience,medical In contrast, pre- and
postsynaptic markers of the functional properties of chandelier axon inputs to the axon initial segment (AIS) of pyramidal neurons exhibit a very protracted maturation. Presynaptically, immunoreactivities for the calcium-binding protein PV and GAT1 in chandelier axon cartridges are not detectable or low at birth, rise (albeit with different developmental Inhibitors,research,lifescience,medical time courses) to peak levels early in postnatal development that are sustained until -15 months of age, and then rapidly decline during adolescence Inhibitors,research,lifescience,medical until stable adult levels are achieved.34,81,82 Since chandelier cartridges are readily visualized with Golgi staining across postnatal development,83 these changes in PV and GAT1 immunoreactivity are
likely to reflect shifts in the concentration of these proteins Metalloexopeptidase rather than changes in the presence of, or in the density of, axon terminals within chandelier axon cartridges.82 Post-synaptically, GABAA receptors containing α2 subunits predominate in pyramidal neuron AIS especially in cortical layers 2-4.84 The density of pyramidal neuron AIS immunoreactive for oc2 subunits is high at birth, then significantly declines during adolescence before achieving stable adult levels:82 These findings indicate that both pre- and postsynaptic markers of GABA neurotransmission undergo significant changes during postnatal development, suggesting that the capacity to synchronize pyramidal neuron output in the prefrontal cortex (PFC) might be in substantial flux until adulthood.
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