TY - JOUR
T1 - Neurosteroid access to the GABAA receptor
AU - Akk, Gustav
AU - Shu, Hong Jin
AU - Wang, Cunde
AU - Steinbach, Joe Henry
AU - Zorumski, Charles F.
AU - Covey, Douglas F.
AU - Mennerick, Steven
PY - 2005/12/14
Y1 - 2005/12/14
N2 - GABAA receptors are a pivotal inhibitory influence in the nervous system, and modulators of the GABAA receptor are important anesthetics,sedatives, anticonvulsants, and anxiolytics. Current views of receptor modulation suggest that many exogenous drugs access and bind to an extracellular receptor domain. Using novel synthetic steroid analogs, we examined the access route for neuroactive steroids, potent GABAA receptor modulators also produced endogenously. Tight-seal recordings, in which direct aqueous drug access to receptor was prevented, demonstrated that steroids can reach the receptor either through plasma membrane lateral diffusion or through intracellular routes. A fluorescent neuroactive steroid accumulated intracellularly, but recordings from excised patches indicated that the intracellular reservoir is not necessary for receptor modulation, although it can apparently equilibrate with the plasma membrane within seconds. A membrane impermeant neuroactive steroid modulated receptor activity only when applied to the inner membrane leaflet, demonstrating that the steroid does not access an extracellular modulatory site. Thus, neuroactive steroids do not require direct aqueous access to the receptor, and membrane accumulation is required for receptor modulation.
AB - GABAA receptors are a pivotal inhibitory influence in the nervous system, and modulators of the GABAA receptor are important anesthetics,sedatives, anticonvulsants, and anxiolytics. Current views of receptor modulation suggest that many exogenous drugs access and bind to an extracellular receptor domain. Using novel synthetic steroid analogs, we examined the access route for neuroactive steroids, potent GABAA receptor modulators also produced endogenously. Tight-seal recordings, in which direct aqueous drug access to receptor was prevented, demonstrated that steroids can reach the receptor either through plasma membrane lateral diffusion or through intracellular routes. A fluorescent neuroactive steroid accumulated intracellularly, but recordings from excised patches indicated that the intracellular reservoir is not necessary for receptor modulation, although it can apparently equilibrate with the plasma membrane within seconds. A membrane impermeant neuroactive steroid modulated receptor activity only when applied to the inner membrane leaflet, demonstrating that the steroid does not access an extracellular modulatory site. Thus, neuroactive steroids do not require direct aqueous access to the receptor, and membrane accumulation is required for receptor modulation.
KW - Anesthesia
KW - GABA
KW - GABA receptor
KW - Inhibition
KW - Membrane
KW - Neurosteroid
UR - http://www.scopus.com/inward/record.url?scp=30744449510&partnerID=8YFLogxK
U2 - 10.1523/JNEUROSCI.4173-05.2005
DO - 10.1523/JNEUROSCI.4173-05.2005
M3 - Article
C2 - 16354918
AN - SCOPUS:30744449510
SN - 0270-6474
VL - 25
SP - 11605
EP - 11613
JO - Journal of Neuroscience
JF - Journal of Neuroscience
IS - 50
ER -