Rapid effects of dorsal hippocampal G-protein coupled estrogen receptor on learning in female mice

Intracellular GPCRs Play Key Roles in Synaptic Plasticity

“…In support of this notion, social learning involves GPER, not ERα or ERβ (98). For example, studies investigating GPER-specific effects in the dorsal hippocampus showed that infusion of the GPER specific agonist, G-1, led to a dose and time-dependent improvement in social recognition and object recognition but not object placement learning in female rats (116). Using a similar paradigm, Kim et al, (117) also found that activation of GPER enhanced object recognition whereas GPER inhibition impaired memory.…”

Rapid actions of oestrogens and their receptors on memory acquisition and consolidation in females

“…Dorsal hippocampal infusion of PPT facilitated object recognition, social recognition and object placement, whereas DPN facilitated only object placement . Although dorsal hippocampal infusion of G‐1 did not affect object placement, it facilitated social and object recognition, in both the home cage and in a Y‐apparatus designed to minimise spatial cues . Similar to effects on gene transcription‐ and protein synthesis‐dependent memory consolidation (see below), these rapid, pre‐acquisition effects depend upon activity of the extracellular signal‐regulated kinase (ERK) pathway because pre‐acquisition inhibition of ERK1/2 activation in the dorsal hippocampus blocked the rapid oestrogenic facilitation of social recognition in ovariectomised mice…”

“…Considered to be necessary for spatial learning and memory, and also to be involved in object discrimination or social recognition, the dorsal hippocampus has been implicated in rapid oestrogen‐induced learning enhancements, both in the presence and absence of contextual spatial cues . Within 40 minutes of systemic administration, 17β‐oestradiol, PPT or G‐1 increased dendritic spine density in the CA1 region of the hippocampus .…”

“…Dorsal hippocampal infusion of 17β‐oestradiol, PPT or G‐1 facilitated learning in various tasks . In ovariectomised mice, dorsal hippocampal infusion of 17β‐oestradiol 15 minutes before the acquisition phases of social recognition, object recognition and object placement tasks facilitated memory at test in paradigms where control animals do not typically learn .…”

“…However, in most cases, pre‐acquisition treatment will affect subsequent phases, especially consolidation, because the treatment and/or its downstream products/effects will remain active during this phase. Therefore, to study effects on acquisition, tasks are commonly designed such that testing occurs immediately after learning and/or before consolidation is complete [Lymer JM, Sheppard PAS, Kuun T, et al Estrogens and their receptors in the medial amygdala rapidly promote social recognition in female mice (unpublished)] or results from pre‐ and post‐acquisition treatments are compared. If pre‐acquisition, but not post‐acquisition, treatment affects memory, this would suggest a treatment effect on acquisition but not consolidation.…”