Progesterone Increases Cell Surface GABAB Receptors in Cultured Cortical Neurons C. Guin Ting Wong1, Yu Tian Wang2, John G. Mielke1, O. Carter Snead III1 1. Brain and Behaviour Program, Hospital for Sick Children, Toronto, Canada. 2. Brain Research Center, Vancouver Hospital and University of British Columbia. Absence seizures are characterized by a loss of consciousness of abrupt onset and offset, that is accompanied by an EEG pattern known as spike and wave discharge (SWD). The GABAB Receptor (GABABR) is believed to mediate the events that lead to this SWD and consequently, absence seizures. The severity of absence seizures vary as a function of the estrus cycle in rat [Persad V.et. al, (2001) SFN Abstract]. GABABR binding also varies as a function of the estrus cycle [Al-Dahan M et. al, Brain Res. 640:33-9]. We hypothesize that fluctuations in GABABR's during the estrus cycle are caused by hormone-induced changes in its intracellular trafficking, and that it is this perturbation that ultimately mediates...