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Biomedical subjects

W J Nowack

Publications and source records attributed to W J Nowack.

31 records · Page 2Linked to original sources
PubMed1983

Effect of hyperthermia on a thalamocortical system in the kitten and the cat: a preliminary study.

Hyperthermia produces many changes in the ongoing electrical activity of the brain. One of the responses which fever can induce is seizure activity. The thalamocortical augmenting response, a complex neurophysiological response, has been related to seizure discharges. The changes in that complex neurophysiological response induced by experimental hyperthermia were assessed in adult cats and in kittens, using analytical methodology first developed in adult cats. The effect of two anticonvulsants (phenytoin and valproate) on those hyperthermia-induced changes in the thalamocortical augmenting response were compared in kittens. The differences between the effects of the two anticonvulsants on the thalamocortical augmenting response can be related to the reported clinical differences between the two anticonvulsants in patients with febrile seizures.

Animals↗
PubMed1983

Development of the thalamocortical augmenting response in the kitten.

Study of the developing central nervous system can lead to better understanding of the mature central nervous system. The thalamocortical augmenting response is a complex neurophysiological response considered to be related to the occurrence of some forms of epileptic activity. Using a paradigm previously developed in adult cats, we assessed the development of the thalamocortical augmenting response in kittens and found that the relative proportion of thalamocortical activity occurring at high frequencies of thalamic stimulation increased with increasing age. Anticonvulsants effective against petit mal seizures also increase the relative proportion of thalamocortical activity following high frequencies of thalamic stimulation. Developmental changes in the thalamocortical augmenting response can be related to the age-dependent decreases in the prevalence of petit mal seizures.

Animals↗
PubMed1979

Cerebellar stimulation: regional effects on a thalamocortical system.

Regional effects of electrical stimulation of the cerebellar surface were quantitatively analyzed. Computer controlled stimulus sequences were delivered to ventrolateral thalamus and evoked responses recorded from ipsilateral sensorimotor cortex in the cat. Threshold and excitability profiles were produced with an on-line computer, and their modification by cerebellar stimulation was determined. The results of electrical stimulation of the cerebellar surface were: (1) depressed excitability from paramedian lobule and lobulus simplex; (2) uniquely elevated thresholds from paramedian lobule; and (3) a profound and long-lasting depression of excitability following termination of lobulus simplex stimulation. In comparison with our anticonvulsant drug studies, these data suggest that cerebellar surface stimulation has a far greater capacity to control excitability and threshold responsiveness of thalamocortical systems. Cerebellar electrode placement and temporal pattern of stimulation appear to be important factors in the production of antiepileptic effects.

Animals↗
PubMed1979

Effects of valproate and ethosuximide on thalamocortical excitability.

Sodium valproate and ethosuximide are anticonvulsants employed in the treatment of petit mal epilepsy; both drugs are considered to be thalamically active. Valproate and ethosuximide both decreased the average evoked response following the second of two stimuli delivered to the ventrolateral thalamus at stimulus frequencies in the region of 3 Hz. Ethosuximide, but not valproate, enhanced the average evoked response at high stimulus frequencies an action shared with several convulsant treatments having different modes of action. The clinical effects of valproate and ethosuximide can be related to this differential modulation of thalamocortical excitability.

Animals↗
PubMed1970

Brain norepinephrine: enhanced turnover after rubidium treatment.

After biosynthesis of norepinephrine was inhibited, treatment of rats for 10 days with rubidium chloride (0.6 milliequivalent per kilogram of body weight) caused an increase in the rate of disappearance of norepinephrine in the brainstem but not in the telencephalon. Also the utilization of intracisternally injected tritiated norepinephrine was increased and was accompanied by a shift in the pattern of norepinephrine metabolism to normetanephrine. These data suggest that greater amounts of neuronally stored norepinephrine were released to central adrenergic receptors.

Animals↗
PubMedDate not supplied

Observations on the effect of morphine on thalamocortical excitability in the cat.

The acute effects of morphine on the thalamocortical augmenting response in the cat were evaluated. The thalamocortical augmenting response was elicited by delivering pairs of pulses to the ventrolateral thalamus and recording from ipsilateral sensorimotor cortex. A biphasic, dose-related, naloxone-attenuable effect on the augmenting response elicited by pulse pairs was observed. Although the clinical significance of those morphine-induced changes is currently uncertain, they can be correlated with the convulsant and anticonvulsant effects of different doses of morphine.

Animals↗
PubMedDate not supplied

Correlative study of interictal electroencephalogram and aura in complex partial seizures.

To understand further relationships of the interictal electroencephalogram to the aura in complex partial seizures (CPS), we studied the interictal EEG and aura in 144 patients with CPS. The ages of the patients studied ranged from 31 to 80 years (average 52.44 years). The duration of seizures ranged from 1 to 60 years (average 15.69 years). Seventy patients (49%) reported auras which were classified according to the guidelines recommended by the Commission of the International League Against Epilepsy. Statistical analysis revealed no relationship between presence, laterality, or localization of EEG abnormality and the number or type of aura. The results emphasize that more factors than electrophysiologic localization alone participate in the determination of aura in CPS. Our data support the position that aura has, at most, a limited relationship to lateralization or localization of interictal cerebral dysfunction in CPS.

Adult↗