Oestradiol Increases Phosphorylation of a Dopamine‐ and Cyclic AMP‐Regulated Phosphoprotein (DARPP‐32) in Female Rat Brain

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Abstract
Recent studies suggest that oestrogen and progestin receptors may be activated by the neurotransmitter dopamine, as well as by their respective ligands. Because intracerebroventricular infusion of D(1), but not D(2), dopaminergic receptor agonists increases oestrous behaviour in oestradiol-primed rats, we wanted to determine if treatment with oestradiol alters the activity of D(1) receptor-associated processes in steroid receptor-containing areas in female rat brain. One D(1) receptor-associated phosphoprotein that may be influenced by oestradiol is a dopamine- and cyclic AMP-regulated phosphoprotein, Mr = 32,000 (DARPP-32). Because DARPP-32 is phosphorylated in response to dopamine acting via a cAMP-dependent protein kinase, it provides a useful marker to examine where in the brain a particular stimulus might be altering the activity of D(1) receptor-containing neurones. To determine if oestradiol alters the phosphorylation of DARPP-32, we stained immunocytochemically brain sections of female rats treated with behaviourally relevant doses of oestradiol or oil vehicle with an antibody that detects only the threonine 34-phosphorylated form of DARPP-32. Behaviourally effective doses of oestradiol increase the phosphorylation of DARPP-32 within the medial preoptic nucleus, bed nucleus of the stria terminalis, paraventricular nucleus of the hypothalamus and the ventromedial nucleus of the hypothalamus, 48 h after treatment. These data suggest that oestradiol increases the activity of D(1) dopamine receptor-associated processes in oestrogen receptor-containing areas of female rat forebrain.