Visual electrophysiological studies

Table 112.1 Visual electrophysiological studies in hypothyroid patients...

A variety of different types of tissue preparation are used to study neurosecretion and synaptic transmission. A classical preparation is the frog NMJ (discussed below). The brain slice has been used for many years for biochemical studies of CNS metabolism and is a useful preparation for electrophysiological studies of synaptic transmission in the CNS. Slices can be oriented to maintain the local neuronal circuitry and can be thin, 0.3 mm, to minimize anoxia. The transverse hippocampal slice is widely used as an electrophysiological preparation to study synaptic plasticity (see Ch. 53). Primary cultures of neurons from selected CNS areas and sympathetic ganglia are also frequently used. They permit excellent visual identification of individual neurons and control of the extracellular milieu, but the normal neuronal connections are disrupted. 

Marciani MG, Cianciulli P, Stefani N, Stefanini F, Peroni L, Sabbadini M, Maschio M, Trua G, Papa G. Toxic effects of high-dose deferoxamine treatment in patients with iron overload an electrophysiological study of cerebral and visual function. Haematologica 1991 76(2) 131-4. 

Ocular electrophysiologic examinations are occasionnally required to evaluate the functional capability of the retina of laboratory animals treated with a test article which may have a detriments effect on retinal function. In order to test the sensitivity of the SYNTHELABO RECHERCHE electroretinograph and to quantify potential fonctional changes, an ocular electrophysiologic study was performed in beagle dogs which received quinine hydrochloride by intravenous infusion at different dose levels. Quinine is known to affect the visual capability to decrease the amplitude and to increase the... 

Ethier AA, Muckle G, Bastien C, Dewailly fi, Ayotte P, Arfken C, Jacobson SW, et al. Effects of environmental contaminant exposure on visual brain development a prospective electrophysiological study in school-aged children. Neurotoxicology 2012 33(5) 1075-85. 

It has been recently reported in the rat that the SNc receives projections from the superior colliculus (Comoli et al., 2003). In this study, tectonigral fibers were seen to establish both asymmetric and symmetric synaptic contacts on TH-positive and TH-negative elements in the SNc. The anatomical and electrophysiological findings of this investigation indicated that visual information relayed to the DA-containing midbrain neurons could be involved in the critical perceptual discriminations that identify biologically salient events. 

The studies on the central nervous system include those on behavioral pharmacology, learning and memory, ligand-specific binding, neurochemistry, visual, auditory, and/or electrophysiology examinations, etc. 

The International Association for the Study of Pain (lASP) has defined pain as an unpleasant sensory and emotional experience that is evoked by actual or potential noxious (i.e. tissue-damaging) stimuli or by tissue injury. Normally, pain is the subjective result of nociception. Nociception is the encoding and processing of noxious stimuli in the nervous system. It can be objectively measured with various techniques, i.e. with electrophysiological recordings. By contrast, pain as a subjective experience can be verbally or visually described by humans, and it cannot be measured objectively However, animals (as well as humans) show reflex responses to acute noxious stimuh, which can be assessed for the relationship between nociception and pain. 

The critical analysis of the physiological, functional, and anatomical responses of the eye to the introduction of exogenous compounds is an integral part of many toxicity studies. Clinical studies conducted with biomicroscopy, indirect ophthalmoscopy, and histopathology allow for the detection of anatomical changes. Electrophysiology and psychophysics provide functional measures of the visual system that complement anatomical analysis. 

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