Biomedical Engineering Reference
In-Depth Information
Ab oligomers were synthesized using an established protocol and characterized
using western blots. Embryonic hippocampal neurons were plated on MEAs and
after 14 days in vitro were treated with either 100 nM Ab oligomers alone or a
combination of Ab and curcumin, an Ab oligomerization inhibitor. Recordings
were obtained over this period of time in order to determine the time course of
both compounds. The observed results were compared with patch clamp data
obtained from similar experiments. Cell death was quantified using a live-dead
assay. When applied to hippocampal neurons cultured on MEAs, Ab had a
pronounced effect on the spontaneous firing of the cells, even at concentrations in
the nanomolar range. Treatment with Ab stopped spontaneous activity
completely and the time until cessation was concentration dependent. Curcumin
was able to partially reverse the loss of spontaneous activity, in accordance with
other patch clamp experiments.
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This study demonstrated that it is possible to develop a high-throughput
MEA screen for the measurement of a drug's effect on functional toxicity of
low concentrations of Ab and this model was the first step for an in vitro
functional model of the development of AD.
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3.10.5.2 Epilepsy
Epilepsy is a serious disorder that affects 50million people globally, a third of
whom are refractory to currently available treatments. Screening of potential
anticonvulsants takes many forms and employs numerous in vitro and in vivo
models of epileptiform activity and seizures, respectively, ranging from cultured
neurons to whole animals. Additionally, extracellular and intracellular elec-
trophysiological recordings from intact brain slices are important techniques
for highlighting potential anti-epileptic properties. The removal of extracellular
Mg
21
ions from bathing fluid or the addition of the potassium channel blocker
4-aminopyridine (4-AP) can induce spontaneous epileptiform activity in a
variety of brain slice preparations. This bioelectrical activity is analogous to
in vivo status epilepticus as measured by EEG.
Hill et al.
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have developed multielectrode arrays recording the Mg
21
-free
and 4-AP models of epileptiform activity in neurophysiologically mature young
adult rat brain slices. MEAs allow extracellular recording from many electrodes
across a large area of the slice, assessing parameters including burst frequency,
duration and amplitude. MEAs also allow these parameters to be measured at
multiple points, better highlighting site-specific differences and patterns of
neuronal activity across the slice. Furthermore, important information on burst
origin, propagation paths, speeds and focal points can be easily and robustly
obtained using MEAs. These are important properties of epileptiform activity
that are not easily or accurately assessed by other means. The method was
validated by examining the effects of two anticonvulsants (felbamate and
phenobarbital) that have been previously reported to exert significant effects in
models using conventional extracellular recording. Burst frequency and
amplitude changed over time in both models in the absence of anticonvulsant
drugs. This is a finding that has significant implications for conventional, as
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