Estrogen receptor α and G-protein coupled estrogen receptor 1 are localized to GABAergic neurons in the dorsal striatum

Abstract

Estrogens affect dopamine transmission in the striatum, increasing dopamine availability, maintaining D2 receptor density, and reducing the availability of the dopamine transporter. Some of these effects of estrogens are rapid, suggesting that they are mediated by membrane associated receptors. Recently our group demonstrated that there is extra-nuclear labeling for ERα, ERβ, and GPER1 in the striatum, but that ERα and GPER1 are not localized to dopaminergic neurons in this region. GABAergic neurons are the most common type of neuron in the striatum, and changes in GABA transmission affect dopamine transmission. Thus, to determine whether ERα or GPER1 are localized to GABAergic neurons, we double labeled the striatum with antibodies for ERα or GPER1 and GABA and examined them using electron microscopy. Ultrastructural analysis revealed that ERα and GPER1 are localized exclusively to extranuclear sites in the striatum, and ∼35% of the dendrites and axon terminals labeled for these receptors contain GABA immunoreactivity. Binding at membrane-associated ERα and GPER1 could account for rapid estrogen-induced decreases in GABA transmission in the striatum, which, in turn, could affect dopamine transmission in this region.

Keywords: Electron microscopy; GPR30; Membrane estrogen receptor alpha; γ-Aminobutyric acid.

Figure 1

The area of the dorsal striatum examined in this experiment.

Figure 2

Electron micrographs demonstrating colocalization of ERα and GABA in the dorsal striatum. A) A dendrite (DEN) containing immunogold labeling for GABA and immunoperoxidase labeling for ERα, which is associated with the membrane and a mitochondrion, forms a synapse with a GABA- and ERα immunoreactive terminal (TER). B) ERα- and GABA -IRs in a dendrite (DEN) that forms a synapse with an unlabeled terminal, and a terminal (TER) containing ERα-IR. Black arrow = immunoperoxidase for ERα, White arrow = immunogold for GABA, bar = 500nm.

Figure 3

Electron micrographs demonstrating colocalization of GPER1 and GABA in the dorsal striatum. A) A dendrite (DEN) containing GABA- and GPER1- IRs associated with microtubules and the plasma membrane. B) A terminal (TER) containing GABA- and GPER1- IRs associated with small synaptic vesicles, which forms a synapse with a GPER1 immunoreactive dendrite (DEN). C) GABA-IR in a soma (SOM) containing GPER1-IR that is associated with a Golgi body. Black arrow = immunoperoxidase for GPER1, White arrow = immunogold for GABA, bar = 500nm.