Electrophysiological measures

Recently, there has been a growth of interest in the development of in vitro methods for measuring toxic effects of chemicals on the central nervous system. One approach has been to conduct electrophysiological measurements on slices of the hippocampus and other brain tissues (Noraberg 2004, Kohling et al. 2005). An example of this approach is the extracellular recording of evoked potentials from neocortical slices of rodents and humans (Kohling et al. 2005). This method, which employs a three-dimensional microelectrode array, can demonstrate a loss of evoked potential after treatment of brain tissue with the neurotoxin trimethyltin. Apart from the potential of in vitro methods such as this as biomarkers, there is considerable interest in the use of them as alternative methods in the risk assessment of chemicals, a point that will be returned to in Section 16.8. 

L-Glutamate acts as an excitatory neurotransmitter at many synapses in the mammalian central nervous system. Electrophysiological measurements and the use of various selective agonists and antagonists indicate that different glutamate receptors co-exist on many neurons. 

The cellular actions of cannabinoids clearly support the proposal that the cannabinoid receptor is inhibitory and, consequently, reduces the firing rate of target neurons. However, this is not wholly confirmed by electrophysiological measurements, which suggest that cannabinoid compounds can stimulate neurons in the hippocampus. This apparent discrepancy may be due to the ability of cannabinoids to inhibit the release of an inhibitory substance in the hippocampus and, thus, produce a net excitation. 

Abstract The ability to clone, express, and electrophysiologically measure currents carried by voltage-gated ion channels has allowed a detailed assessment of the action of pyrethroids on various target proteins. 

Lobster chemoreceptor cells show a great diversity of filter properties. Electrophysiological measurements show that each receptor cell is tuned not only to one or a few preferred compounds (12, 13) but also to a preferred frequency (14, 15). Temporal resolution in chemoreception is affected by at least five different stimulus parameters rate of stimulus concentration increase (= pulse slope), amplitude and duration of a... 

Joyce CA, Paller KA, Mclsaac HK, Kutas M. (1998). Memory changes with normal aging behavioral and electrophysiological measures. Psychophysiology. 35(6) 669-78. 

The greater conductivity of an ion-exchanger solution containing the potassium salt of anion XVI in solvent 3-o-nitroxylene (Corning No. 476200) [13a] is a reason for the popularity of this system for electrophysiological measurements using ion-selective microelectrodes [216]. Application of this sensor is so widespread that only reviews and books will be mentioned, for microelectrodes in intracellular measurements [23, 32, 78, 86, 211, 217] and for the determination of K in the intercellular liquid [78]. A working valinomycin microelectrode has also been constructed [166]. 

Electrophysiologically measured thresholds for butanoic acid and ethanethiol in Manx shearwater Puffinus puffinus) and black-footed albatross Diomedea nigripes) are as low as 0.01 ppm (Wenzel and Sieck, 1966). More electrophysiologi-cal thresholds for some compounds in tree swallows and cedar waxwings (Clark, 1991), starlings (Clark and Smeraski, 1990), and brown-headed cowbirds (Clark and Mason, 1989) are listed in Table 5.4. 

Central electrophysiological measures are also partially supportive, in that evoked response and computer-assisted electroencephalogram (EEG) mapping indicate bipolar-unipolar differences, with right-sided abnormalities more common in bipolar patients. Further, P300 topographical differences have been reported between schizophrenic and psychotic manic patients (41). 

H. Tanaka, T. Yoshinobu and H. Iwasaki, Application of the chemical imaging sensor to electrophysiological measurement of a neural cell, Sens. Actuators B Chem., 59(1) (1999) 21-25. 

Chetoni, P., et al. 2003. Ocular toxicity of some corneal penetration enhancers evaluated by electrophysiology measurements on isolated rabbit corneas. Toxicol In Vitro 17 197. 

Electrophysiological measurement in which a sensory (flight flash, tone) or cognitive signal stimulates a response that is detected from the scalp or cortex. Part of a gene that encodes information present in messenger RNA. 

Electrophysiologic Measures of Diabetic Neuropathy Mechanism and Meaning... 

Briefly, evaluation of the effects of hypnotics on sleep physiology and sleep architecture, as measured by electroencephalography, has received increased attention. Continuous all-night electrophysiological measurement of sleep termed polysomnography (PSG) has made it possible to evaluate the action of hypnotics on sleep. PSG assessment as a means of evaluating the hypnotic effects of a drug candidate is now required by the U.S. FDA. 

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