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Biomedical subjects

J R Ison

Publications and source records attributed to J R Ison.

78 records · Page 5Linked to original sources
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Reflex modification as a test for sensory function.

Reflex modification is a versatile procedure for the assessment of sensory function because it can provide information about the responses of several sensory systems to both weak and intense stimuli. The procedure has two elements: The elicitation of some reflex, such as the acoustic startle reflex, and the modification of that reflex by preliminary stimuli. In these experiments we used reflex modification and reflex elicitation procedures to examine the normal development of auditory function in rats and to evaluate alterations in auditory function produced by physical and toxic insult. Adult rats exposed to octave bands of noise demonstrated frequency-specific deficits on a test of reflex modification, but not reflex elicitation. In the studies of developing rats, reflex elicitation appeared by postnatal day 12 and modification around day 14. Frequency-specific increases in both measures suggested that the phenomena were sensitive to auditory development and, not simply, motor development. Exposure to kanamycin on postnatal days 8 to 16 produced dose-related deficits in the ability to detect stimuli at 32 and 16 kHz, but not 4 and 0.8 kHz. These effects were observed in the absence of changes in reflex elicitation. The results demonstrate that reflex modification procedures provide more sensitive and specific information than that provided by the use of reflex elicitation alone.

Acoustic Stimulation↗
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Prenatal diazepam exposure in rats: long-lasting functional changes in the offspring.

Adult (90-100 day-old) rats exposed prenatally (13-20 days of gestation) to diazepam (DZ) at 1.0, 2.5, or 10 mg/kg/day, were examined for functional deficits. Tests were designed to (1) correlate with known neural alterations induced by the prenatal exposure, or (2) to address the problem of developing tests of functional teratology in animals which have relevance to complex human functions. The careful selection of functional tests has disclosed several effects of prenatal DZ exposure on adult rat progeny. The dose-effect relationship was found to vary with the different tests, indicating that a thorough evaluation of the consequences of prenatal drug exposure necessitates utilization of several functional approaches. The results of these studies on the effects of prenatal exposure to DZ support the hypothesis that in utero exposure to drugs targeted for action on the central nervous system can induce long-lasting alterations on the neural substrates of behavior on the offspring with resulting functional consequences.

Animals↗
PubMedDate not supplied

Reflex modification as an objective test for sensory processing following toxicant exposure.

Test batteries for assessing psychological function following toxic exposure should evaluate sensory processes. Sensory function has intrinsic importance as an endpoint measure, and because performance in other behavioral tests typically requires that the organism can detect significant environmental events, its evaluation is necessary to the proper interpretation of other tests. In addition, the psychological and physiological principles concerning sensory function are relatively well known, as is the comparative structure of the sensory systems across species. This knowledge provides the necessary empirical and theoretical base for extrapolating sensory effects of toxic exposure across species. An analysis of sensory function is described that uses the demonstration of reflex inhibition by irrelevant stimuli as an objective measure of stimulus detection. Two basic parameters of reflex inhibition in several species are detailed, its sensitivity to near threshold stimuli is discussed, and the effects of sensory dysfunction on reflex inhibition are demonstrated. This method has much to recommend it for toxicology, including its rapidity, its objectivity, its sensitivity, and its suitability for use in both humans and a variety of laboratory animals.

Animals↗