S4B, available atwww

S4B, available atwww.jneurosci.orgas supplemental material) (Shu et al., 2007). neurosteroid synthesis, or 17PA [17-phenyl-(3,5)-androst-16-en-3-ol], a blocker of neurosteroid effects on GABAAreceptors. Moreover, the synaptic effects were mimicked by a combination of clonazepam with FGIN (2-[2-(4-fluorophenyl)-1H-indol-3-yl]-N,N-dihexylacetamide), a selective TSPO agonist, or a combination of clonazepam with exogenous allopregnanolone. Consistent with thesein vitroresults, finasteride abolished the effects of midazolam on contextual fear learning when administrated 1 d before midazolam injection. Thus, dual activation of CBRs and TSPO appears to result in unique actions of clinically important BDZs. Furthermore, endogenous neurosteroids CPI-203 are shown to be important regulators of pyramidal neuron function and synaptic plasticity. == Intro == Benzodiazepines (BDZs) are widely used to treat panic, sleeping disorders, and epilepsy, and also as intravenous anesthetics in which sedation and amnesic effects are exploited for medical benefit (Olkkola and Ahonen, 2008). BDZs are known to depress CNS activity via central BDZ receptors (CBRs) that are integral components of particular GABAAreceptors (GABAARs) (Rudolph and Mhler, 2004). BDZs also bind intracellular receptors on mitochondria that are unique from CBRs and referred CPI-203 to as peripheral BDZ receptors (PBRs) based on manifestation at non-CNS loci (Gavish et al., 1999). PBRs are now known as translocator protein (18 kDa) (TSPO) (Papadopoulos and Lecanu, 2009), reflecting their manifestation in the CNS and ability to bind additional ligands (Wayne et al., 2006). TSPO activation promotes cholesterol trafficking and synthesis of molecules derived from cholesterol, and regulates multiple cellular processes including apoptosis (Hirsch et al., 1998), immune function (Marino et al., 2001), and neurosteroid production (Costa et al., 1994). Neurosteroids, including 3-hydroxy-5-prenan-20-one [allopregnanolone (AlloP)], are generatedde novoin the CNS and are potent and effective modulators of GABAARs (Belelli and Lambert, 2005), probably contributing to medical effects of particular psychotropic medications (Kumar et al., 2009). Recent studies show that TSPO agonists have anxiolytic effects mediated by endogenous GABAergic neurosteroids (Bitran et al., 2000;Da Settimo et al., 2008). Importantly, excitatory neurons look like the primary source of these neurosteroids (King et al., 2002;Ags-Balboa et al., 2006), raising the possibility that neurosteroids are important local regulators of pyramidal neuron function. We hypothesized that BDZ-mediated neurosteroid production may modulate pyramidal neuron firing and synaptic function. To test this, we compared midazolam, an anesthetic BDZ CPI-203 used clinically for its amnesic properties, and clonazepam, an anxiolytic and anticonvulsant with relatively selective actions on CBRs (Mukhin et al., 1989;Gavish et al., 1999). We compared effects on neurosteroid production, network inhibition, and synaptic plasticity in the CA1 region of rat hippocampal slices, and,in vivo, on a form of hippocampal-dependent learning. We found that midazolam, but not clonazepam, enhances a specific form of network inhibition and inhibits long-term potentiation (LTP) and learning inside a neurosteroid-dependent fashion. == Materials and Methods == == == == == == Animals. == Protocols for animal use were authorized by the Washington University or college Animal Studies Committee in accordance with the National Institutes of HealthGuide for the Care Igf1 and Use of Laboratory Animals. Rats were maintained on a standard 12 h light/dark cycle withad libitumaccess to food. == Hippocampal slice preparation. == Hippocampal slices were prepared from postnatal day time 3032 male Sprague Dawley rats purchased from Harlan (Zorumski et al., 1996). Rats were anesthetized with isoflurane and decapitated. Slices were slice transversely into 500 m slices using a rotary slicer in artificial CSF (ACSF) comprising the following (in mm): 124 NaCl, 5 KCl, 2 MgSO4, 2CaCl2, 1.25 NaH2PO4, 22 NaHCO3, 10 glucose, bubbled with 95% O2/5% CO2at 46C. Acutely prepared slices were placed on mesh in 10 ml CPI-203 beakers comprising gassed ACSF and managed for at least 1 h CPI-203 at 30C before experiments. == Immunohistochemistry. == Hippocampal slices utilized for immunohistochemistry were in the beginning screened by electrophysiology. Using paired-pulse activation delivered to the Schaffer security (SC) pathway at an interval of 21 ms, we selected slices showing stable paired-pulse facilitation of dendritic EPSPs and paired-pulse major depression of human population spikes (PSs). Selection based on physiological screening markedly diminished slice-to-slice variability in staining for 5-reduced neurosteroids and was consistent with the criteria used for selecting slices utilized for electrophysiological studies. Slices analyzed immunochemically were incubated with numerous reagents in independent 10 ml.