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Abstract
<p class="first" id="P2">The current study examined the effect of age on both glutamatergic
and GABAergic signaling
in the rodent medial prefrontal cortex (mPFC), with an emphasis on revealing novel
changes contributing to increased inhibition in age. Whole-cell patch clamp recordings
were obtained from layer 2/3 mPFC pyramidal neurons in acute cortical slices prepared
from either young (4 month) or aged (20–24 month) male F344 rats. Results indicated
that GABA
<sub>B</sub> receptors on GABAergic, but not on glutamatergic, inputs to layer 2/3
pyramidal cells
are tonically activated by ambient GABA in young animals, and further demonstrated
that this form of tonic inhibition is significantly attenuated in aged mPFC. Moreover,
concurrent with loss of tonic presynaptic GABA
<sub>B</sub> autoreceptor activation, layer 2/3 pyramidal cells in aged mPFC are subjected
to
increased tonic activation of extrasynaptic GABA
<sub>A</sub> and GABA
<sub>B</sub> receptors. These data demonstrate a shift in the site of GABA
<sub>B</sub>R mediated inhibitory tone in the aged mPFC that clearly promotes increased
inhibition
of pyramidal cells in aged animals, and that may plausibly contribute to impaired
executive function.
</p>