Rudick CN, Gibbs RB, Woolley CS (2002) Estrogen-induced disinhibition of hippocampal CA1 pyramidal cells depends on basal forebrain cholinergic neurons. Neuroscience 2002 Abstracts 740.6. Society for Neuroscience, Orlando, FL.
Summary: Estrogen (E) increases dendritic spine and synapse density on hippocampal pyramidal cells, both in vivo and in vitro. In both cases, the increase in spine/synapse density is preceded by transient disinhibition. Based on in vitro studies, this transient disinhibition is likely to be involved in the mechanism of the subsequent increase in spine density. In adult female rats, where E increases spine/synapse density on CA1 pyramidal cells, it is unknown whether E acts within the hippocampus itself and/or through hippocampal afferents to regulate synaptic changes. Considerable evidence suggests that the basal forebrain (BF) cholinergic system could be involved in mediating E’s effects in the hippocampus. Therefore, we tested the ability of E to disinhibit CA1 pyramidal cells in adult female rats in which BF cholinergic neurons were eliminated by infusion of 192IgG-saporin toxin (SAP) into the medial septum. Two weeks after SAP or SHAM lesion, rats were ovariectomized and treated with E or oil (O) 3 days later. Synaptically evoked inhibitory postsynaptic currents (eIPSCs) and miniature IPSCs (mIPSCs) in CA1 pyramidal cells were evaluated 24h after E or O, the timepoint at which disinhibition occurs. As previously shown, E decreased eIPSC amplitude and mIPSC frequency at 24h. Additionally, E-induced disinhibition was significantly reduced in SAP lesioned rats, but it was not completely blocked. These data demonstrate that the BF cholinergic system is involved in E-induced disinhibition of CA1 pyramidal cells, but that other cells may also be involved.
Related Products: 192-IgG-SAP (Cat. #IT-01)