17α Estradiol promotes plasticity of spared inputs in the adult amblyopic visual cortex

The promotion of structural and functional plasticity by estrogens is a promising therapy to enhance central nervous system function in the aged. However, how the sensitivity to estrogens is regulated across brain regions, age and experience is poorly understood. To ask if estradiol treatment impacts structural and functional plasticity in sensory cortices, we examined the acute effect of 17 Estradiol in adult Long Evans (LE) rats following chronic monocular deprivation, a manipulation that reduces the strength and selectivity of deprived eye vision. Chronic monocular deprivation decreased thalamic input from the deprived eye to the binocular visual cortex and accelerated short-term depression of the deprived eye pathway, without changing the total density of excitatory synapses. Importantly, we found that the classical estrogen receptors ER and ER{beta} are robustly expressed in the adult visual cortex, and that a single dose of 17 Estradiol increased the size of excitatory postsynaptic densities, reduced the expression of parvalbumin and decreased the integrity of the extracellular matrix. Furthermore, 17 Estradiol enhanced experience-dependent plasticity in the amblyopic visual cortex, and promoted response potentiation of the pathway served by the non-deprived eye. The promotion of plasticity at synapses serving the non-deprived eye may reflect selectivity for synapses with an initially low probability of neurotransmitter release, and may inform applications to remap spared inputs around a scotoma or a cortical infarct