8-Hydroxyquinolylnitrones as multifunctional ligands for the therapy of neurodegenerative diseases

We describe the development of quinolylnitrones(QNs)as multifunctional ligands inhibiting cholinesterases(ChEs:acetylcholinesterase and butyrylcholinesterase—h BChE)and monoamine oxidases(hMAO-A/B)for the therapy of neurodegenerative diseases.We identified QN 19,a simple,low molecular weight nitrone,that is readily synthesized from commercially available 8-hydroxyquinoline-2-carbaldehyde.Quinolylnitrone 19 has no typical pharmacophoric element to suggest ChE or MAO inhibition,yet unexpectedly showed potent inhibition of h BChE(IC50=1.06±0.31 nmol/L)and h MAO-B(IC_(50)=4.46±0.18μmol/L).The crystal structures of 19 with hBChE and hMAO-B provided the structural basis for potent binding,which was further studied by enzyme kinetics.Compound 19 acted as a free radical scavenger and biometal chelator,crossed the blood—brain barrier,was not cytotoxic,and showed neuroprotective properties in a 6-hydroxydopamine cell model of Parkinson's disease.In addition,in vivo studies showed the anti-amnesic effect of 19 in the scopolamine-induced mouse model of AD without adverse effects on motoric function and coordination.Importantly,chronic treatment of double transgenic APPswe-PS1δE9 mice with 19 reduced amyloid plaque load in the hippocampus and cortex of female mice,underscoring the disease-modifying effect of QN 19.

Involvement of basolateral amygdala GABAA receptors in the effect of dexamethasone on memory in rats

In this study we investigated whether GABAA receptors of the basolateral amygdala(BLA) interact with the effect of dexamethasone on the retrieval stage of memory.Adult male Wistar rats were bilaterally cannulated in the BLA by stereotaxic surgery.The animals were trained in step-through apparatus by induction of electric shock(1.5 mA,3 s) and were tested for memory retrieval after 1 d.The time of latency for entering the dark compartment of the instrument and the time spent by rats in this chamber were recorded for evaluation of the animals' retrieval in passive avoidance memory.Administration of dexamethasone(0.3 and 0.9 mg/kg,subcutaneously(s.c.)),immediately after training,enhanced memory retrieval.This effect was reduced by intra-BLA microinjection of muscimol(0.125,0.250 and 0.500 μg/rat),when administered before 0.9 mg/kg of dexamethasone.Microinjection of bicuculline(0.75 μg/rat,intra-BLA) with an ineffective dose of dexamethasone(0.1 mg/kg,s.c.) increased memory retrieval.However,the same doses of muscimol and bicuculline without dexamethasone did not affect memory processes.Our data support reports that dexamethasone enhances memory retrieval.It seems that GABAA receptors of the BLA mediate the effect of dexamethasone on memory retrieval in rats.