Evaluating the protective effect of etazolate on memory impairment, anxiety- and depression-like behaviors induced by post traumatic stress disorder.

Post-traumatic stress disorder (PTSD) is a neuropsychiatric disorder that develops after an individual experiences severe life-threatening traumatic stress. Etazolate is a selective phosphodiesterase-4 inhibitor that is specific for cAMP. Etazolate showed anxiolytic and antidepressant activity, and could be useful in managing PTSD co-morbidities. The current study was done to evaluate the role of etazolate in preventing PTSD induced memory impairment, anxiety and depression-like symptoms. PTSD was induced in rats using single prolonged stress model. Etazolate was administered via oral gavage at a dose of 1mg/kg/day. The radial arm water maze was used to assess learning and memory. The elevated plus maze, open field, and tail suspension tests were conducted to test anxiety- and depression-like symptoms. The PTSD was associated with short- and long-term memory impairment, which was prevented by etazolate administration. Moreover, PTSD was associated with symptoms of anxiety and depression. Etazolate administration prevented these symptoms. In conclusion, our data suggests that memory impairment, anxiety, and depression symptoms that are induced by PTSD can be prevented using etazolate.

Radiation inactivation of brain [35S]t-butylbicyclophosphorothionate binding sites reveals complicated molecular arrangements of the GABA/benzodiazepine receptor chloride channel complex.

[35S]t-Butylbicyclophosphorothionate ([35S]TBPS), a bicyclic cage convulsant, binds to the anion gating mechanism of the GABA/benzodiazepine receptor chloride channel complex. Using a carefully calibrated radiation inactivation technique, the molecular weight of [35S]TBPS binding complexes from frozen rat cerebral cortex was estimated to be 137,000 daltons. The GABA agonist muscimol reduced [35S]TBPS binding to 0-10% of the control value, in a way which is independent of the radiation dose. This shows that the GABA receptor (Mw = 55,000 daltons) is included in the 137,000-dalton [35S]-TBPS binding complex; the [35S]TBPS binding protein alone accounts for 137,000-55,000 = 82,000 daltons. The pyrazolopyridazine etazolate (SQ 20.009) and etomidate in appropriate concentrations both reduced specific binding of [35S]TBPS. The ability of SQ 20.009 and etomidate to reduce [35S]TBPS binding was greatly reduced by exposure to low radiation doses, suggesting that SQ 20.009 and etomidate reduce [35S]TBPS binding by an allosteric mechanism requiring a molecular structure of 450,000-500,000 daltons. Benzodiazepine agonists (ethyl 4-methoxymethyl-6-benzyloxy-beta-carboline-3-carboxylate, ZK 93423) and inverse agonists (methyl 6,7-dimethoxy-4-ethyl-beta-carboline-3-carboxylate, DMCM) enhance and reduce [35S]TBPS binding, respectively, in repeatedly frozen and washed membrane preparations. The effects of ZK 93423 and DMCM on [35S]TBPS binding disappeared upon exposure of membranes to low radiation doses. This suggests that the benzodiazepine receptor site interacts allosterically with the [35S]TBPS binding site, requiring a molecular complex of at least c. 400,000 daltons. The [35S]TBPS site alone in these latter conditions of membrane preparation (repeatedly frozen/washed) revealed a molecular weight of 221,000 daltons (TBPS-site + GABA receptor + unknown structures). The number of binding sites for [35S]TBPS (145 pmol/g tissue) was only slightly higher than for [3H]flunitrazepam (130 pmol/g tissue) in cerebral cortex. These results are all consonant with the conclusion that the GABA/BZ receptor chloride channel complex is composed of highly integrated multimeric subunits, tentatively accounted for by a tetramic complex of molecular weight 548,000 daltons.