Skip to main content
. Author manuscript; available in PMC: 2016 Jul 1.
Published in final edited form as: Trends Mol Med. 2015 Jun 9;21(7):450–460. doi: 10.1016/j.molmed.2015.05.002

Figure 3.

Figure 3

Age-related dysregulation of tonic GABA signaling at prefrontal cortex (PFC) synapses. The schematic shows representative presynaptic terminals from young adult and aged rat PFC that illustrate age-related changes in GABAergic signaling protein expression. Presynaptically, expression of glutamic acid decarboxylase (GAD) is upregulated in the aged PFC, and there is a concurrent reduction in expression of GABA transporter GAT-1 and GABABR1a [11,14]. These changes suggest an imbalance in the capacity to produce GABA relative to the ability to clear synaptic GABA or inhibit its further release. This biochemical evidence is corroborated by electrophysiological findings that suggest that the loss of autoreceptors manifests as a reduction in presynaptic GABA tone that normally limits further GABA release [89]. Consequently, there is an increase in extracellular GABA that increases the tonic activation of postsynaptic GABA receptors [89]. Together, these alterations would be expected to confer an agerelated increase in basal inhibition of PFC pyramidal neurons.