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Query: UMLS:C0596131 (audiogenic seizure)
 315 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A number of neurochemical and behavioral similarities exist between the genetically epilepsy-prone (GEPR) rat and rats made hypothyroid at birth. These similarities include lower brain monoamine levels, audiogenic seizure susceptibility and lowered electroconvulsive shock seizure threshold. Given these similarities, thyroid hormone status was examined in GEPR rats. Serum samples were collected from GEPR-9 and non-epileptic control rats at 5, 9, 13, 16, 22, 31, 45, 60, 90, 150 and 350 days of age. Serum thyroxine (T4) levels were significantly lower in GEPR-9 rats compared to control until day 22 of age. GEPR-9 thyrotropin (TSH) levels were significantly elevated during the period of diminished serum T4. GEPR-9 triiodothyronine (T3) levels were lower than control throughout the first year of life. The data indicate that the GEPR-9 rat is hypothyroid from at least the second week of life up to 1 year of age. The critical impact of neonatal hypothyroidism on brain function coupled with the development of the audiogenic seizure susceptible trait by the GEPR-9 rat during the third week after birth suggests that neonatal hypothyroidism could be one etiological factor in the development of the seizure-prone state of GEPR-9 rats.
Epilepsy Res
PMID:Evidence of hypothyroidism in the genetically epilepsy-prone rat. 319 82

Our previous studies have shown an increase in the number of GABAergic and total neurons in the inferior colliculus (IC) of the genetically epilepsy-prone rat (GEPR-9) as compared to the non-seizing Sprague-Dawley (SD) rat. To determine whether an increase in neuron number in the IC is genetically associated with seizure behavior, seizing and non-seizing offspring of GEPR-9 and SD progenitor strains were studied as well as offspring from backcrosses made with F1 and either GEPR-9 or SD rats. In addition, the ontogeny of seizure behavior was studied in seizing rats from these same backgrounds. The development of seizure behavior in GEPR-9s was shown to be dependent on age and the number of exposures to sound stimulus up until the age of 9 weeks. The F1 and F2 generations displayed different audiogenic seizure profiles than those of the two progenitor strains. In the F1 generation, the ratio of seizing to non-seizing rats was always greater than 3:1, and the distribution of seizure scores was similar for males and females. In addition, the off-spring from backcrosses made with F1 rats (high or low seizing) and GEPR-9s displayed maximal audiogenic response scores (ARS) of 9, a characteristic of the GEPR-9s used in this study. The results of these genetic studies indicate a polygenetic inheritance of this autosomal dominant trait of audiogenic seizure susceptibility. For the quantitative study of neuronal density in the IC, neurons were counted from cresyl violet-stained preparations from seizing and non-seizing F1 and F2 rats, backcrosses from different categories and age-matched SD rats. Statistically significant increases in the number of both small (70% increase) and medium-sized (14% increase) neurons occurred in the high seizing animals (ARS = 7-9) as compared to either the non-seizing F2 or SD rats. In addition, a significant increase in the number of small neurons (77% increase) occurred in the high seizing offspring of the F1 X GEPR-9 backcross as compared to that of the non-seizing offspring of the F1 X SD backcross. The data from 25 rats generated a 0.9 coefficient of linear correlation between ARS and the number of small neurons. The results from the anatomical studies suggest that the inheritance of audiogenic seizures appears to be closely linked to the increase in cell number. Therefore, the increase in cell number in the IC may be an important determinant of seizure behavior for GEPR-9s.
Epilepsy Res
PMID:Anatomical and behavioral analyses of the inheritance of audiogenic seizures in the progeny of genetically epilepsy-prone and Sprague-Dawley rats. 319 4

Abnormalities in noradrenaline-mediated neurotransmission have been advocated as a basis of the age-related susceptibility of DBA/2J mice to generalised convulsions induced by auditory stimulation. We have measured the kinetics of synaptosomal high-affinity noradrenaline uptake in 5 brain regions of DBA/2J mice at ages before, during and after their maximal susceptibility to audiogenic seizures, and age-matched C57 BL/6 mice, a strain resistant to audiogenic seizures at all ages. No differences were found between the two strains of mice in any of the brain regions studied. Abnormalities of high-affinity noradrenaline uptake do not contribute to audiogenic seizure susceptibility of DBA/2J mice.
Epilepsy Res 1987 Mar
PMID:Synaptosomal high-affinity noradrenaline uptake does not differ between mice susceptible (DBA/2J) and resistant (C57 BL/6) to audiogenic seizures. 350 89

In this chapter, we review the major inherited convulsive disorders found in mice and discuss their possible relationship to specific clinical seizure disorders in humans. These disorders in mice include audiogenic seizures, the epilepsy (El) mouse, various spontaneous seizures, the tottering/leaner syndrome, seizures associated with cerebellar abnormalities, seizures associated with myelin disorders, and alcohol withdrawal seizures. We find that for most major types of epilepsy in humans, there exists a similar counterpart in the mouse. Because human and rodent nervous systems respond similarly to seizure-provoking stimuli, it is possible that biochemical and physiological mechanisms of naturally occurring convulsive disorders are also similar in these species. The use of recombinant inbred (RI) and congenic mouse strains for genetic and biochemical studies of audiogenic seizures is presented. Using these strains, we have identified a major gene, Ias, that inhibits the spread of seizure activity. This gene was found through its close linkage with the Ah locus on chromosome 17. We also found that juvenile-onset and adult-onset audiogenic seizures are controlled by different genetic systems. The problem of juvenile-onset audiogenic seizure susceptibility is especially interesting because these seizures are genetically associated with an ecto-Ca2+-ATPase deficiency among the RI strains. This deficiency is the first neurochemical trait found to be inherited together with an idiopathic convulsive disorder, and may represent a potentially important basic mechanism of epilepsy. Because the brains of human epileptics are generally inaccessible for neurochemical research, the epileptic mouse mutants offer a convenient means of pursuing this type of research. The well-known genetic constitution of the mouse, together with the availability of numerous physiologically distinct convulsive disorders, makes the mouse ideally suited for molecular, genetic, and biochemical studies of convulsive behavior.
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PMID:Inherited convulsive disorders in mice. 351 45

The EEG of 20 Wistar rats inbred for audiogenic seizures was recorded during 40 daily auditory stimuli 90 s long. The first stimuli provoked wild running, with no cortical EEG abnormality, and then a tonic phase with a characteristic EEG of a brief flat trace 2 to 3 s long followed by low-amplitude regular activity, 10 to 12 c/s, lasting 40 to 60 s. The lack of paroxysmal EEG patterns suggests that the cortex plays only a minor role in audiogenic seizure development. After 5 to 15 daily stimuli, the EEG during the running period exhibited brief spike and spike-wave discharges preceding the EEG pattern of the tonic phase. After a few more daily stimuli these paroxysmal discharges progressively increased in amplitude and duration, overlapping with the regular activity of the tonic phase. After 20 to 30 stimuli, only high-amplitude spikes and spike-waves, 1 to 10 c/s, were seen for 40 to 120 s. The modified EEG persisted 2 to 4 months after daily stimulation was discontinued. Thus, with stimulus repetition, a paroxysmal discharge progressively involved cortical structures. These data suggest that repetition of audiogenic seizures induced a phenomenon related to kindling in Wistar rats susceptible to sound-induced epilepsy.
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PMID:Kindling of audiogenic seizures in Wistar rats: an EEG study. 358 60

The genetically epilepsy-prone rat (GEPR) is abnormally susceptible to induction of seizures by acoustic stimulation. The inferior colliculus (IC) is critically important to audiogenic seizure susceptibility. The GEPR is more susceptible to induction of audiogenic seizures at 12 kHz than at other pure tone frequencies. IC neurons in the GEPR exhibit significantly elevated response thresholds and broader tuning characteristics than normal. These findings along with previous neurophysiological and anatomical data suggest that a hearing deficit occurs in the GEPR. IC neurons in the GEPR exhibit a significantly elevated incidence of a response pattern with a peak of activity at the beginning and end of the stimulus, the onset-offset response. This response pattern occurs at 12 kHz and at characteristic frequency with high stimulus intensities and may represent an afterdischarge phenomenon. The onset-offset pattern may be a manifestation of central mechanisms developed to compensate for reduced peripheral auditory input that appears to be involved in the hearing deficit of the GEPR. Such compensatory mechanisms may involve alterations of the actions of neurotransmitters of the brain-stem auditory nuclei. GABA is implicated as an inhibitory transmitter in the IC. Iontophoretic application of GABA or a benzodiazepine produces significantly less inhibition of IC neurons of the GEPR than of the normal rat. Endogenous sound-induced (binaural) inhibition which is suggested to be GABA-mediated is also significantly reduced in IC neurons of the GEPR. Iontophoresis of the GABAA antagonist, bicuculline, often converts normal response patterns in the IC to onset-offset responses seen with high incidence in GEPR IC neurons, suggesting that the decreased effectiveness of GABA may lead to the onset-offset prevalence. This reduced effectiveness of inhibition may be unable to compensate for the rise in the putative excitatory transmitter, aspartate, in IC during high intensity acoustic stimulation in the GEPR. These altered transmitter actions may be important mechanisms subserving initiation of audiogenic seizures in the genetically epilepsy-prone rat.
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PMID:Inferior colliculus neuronal response abnormalities in genetically epilepsy-prone rats: evidence for a deficit of inhibition. 374 11

Pharmacological studies demonstrate a reciprocal relationship between both noradrenergic and serotonergic transmission and audiogenic seizure severity and susceptibility in the genetically epilepsy-prone rat (GEPR). In contrast, drug-induced changes in the neurochemical indices of dopaminergic activity do not result in alterations in seizure severity. These pharmacological investigations led to the hypothesis that both noradrenergic and serotonergic neurons are capable of regulating seizure severity in the GEPR. Pharmacological investigations also provided evidence that monoaminergic neurons serve as determinants of seizure susceptibility in these epileptic animals. The GEPR is susceptible to environmentally-induced seizures which cannot be precipitated in neurologically normal subjects. Drug studies suggest that monoaminergic decrements serve as one set of susceptibility determinants. However, non-monoaminergic abnormalities also play important roles in the seizure predisposition which characterizes the GEPR. Pathophysiological studies have confirmed and extended the concepts generated by the pharmacological investigations. Noradrenergic and serotonergic deficits do indeed characterize the seizure naive state of the GEPR. These studies have provided a basis for tentative identification of areas of the brain in which monoaminergic abnormalities regulate seizure severity and susceptibility. Monoaminergic defects in some areas such as the thalamus may regulate both susceptibility and severity. In other areas, defects may regulate only severity or susceptibility. In the striatum, noradrenergic defects do not appear to be present and probably are not determinants of the epileptic state of the GEPR.
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PMID:Noradrenergic and serotonergic determinants of seizure susceptibility and severity in genetically epilepsy-prone rats. 374 29

A bilateral mechanical lesion of the midbrain and pontine tegmentum was found to abolish completely the tonic components of sound-induced seizures in genetically epilepsy-prone rats (GEPR) that display tonic-clonic seizures. Correlations between varied lesions placements and effects on maximal audiogenic seizures provided evidence that damage to the nucleus reticularis pontis oralis (RPO) of the midbrain and pontine reticular formation (RF) was responsible for the seizure-attenuating effects. Moreover, electrolytic lesions of the pontine RF involving the RPO nucleus were found to abolish the tonic components of the maximal audiogenic seizure. Additionally, bilateral mechanical lesions involving the RPO nucleus were found to attenuate the clonic components of sound-induced seizures in GEPR that display only running seizures and clonus. These findings are consistent with previous studies showing that pontine tegmental lesions attenuate the tonic components of maximal electroshock- and pentylenetetrazol-induced seizures, and lend further support to the hypothesis that all generalized tonic seizures share a common neural substrate. The role of the brainstem RF in tonic versus clonic convulsions is discussed in light of the present findings.
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PMID:Effect of midbrain and pontine tegmental lesions on audiogenic seizures in genetically epilepsy-prone rats. 398 48

The preferential alpha-2 noradrenergic agonists, clonidine (0.2--0.4 mg/kg), oxymetazoline (2.5--10.0 mg/kg) and UK 14,304 (0.6 mg/kg), when given i.p., reduce the severity of audiogenic seizures in 19- to 26-day-old DBA/2 mice. This protective effect can be diminished or reversed by alpha-2 noradrenergic antagonists such as yohimbine (2.5 mg/kg) or piperoxan (20--50 mg/kg) given i.p. or phentoalamine (100 micrograms) given intracerebroventricularly. It is not reversed by the preferential alpha-1 noradrenergic antagonist phenoxybenzamine (5 mg/kg) given i.p. Yohimbine, (1--2.5 mg/kg), piperoxan (20--50 mg/kg) or phenoxybenzamine (5 mg/kg) given i.p. alone did not change the severity of audiogenic seizure responses. Phentolamine (10--100 micrograms) or prazosin (10--50 micrograms) given intracerebroventricularly induced spontaneous limb myoclonus in some mice. Audiogenic seizure responses were unchanged after phentolamine (10--100 micrograms) but were reduced after prazosin (25--50 micrograms). Activation of a receptor pharmacologically similar to the peripheral alpha-2 noradrenergic receptor protects against seizures in this epilepsy model.
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PMID:Noradrenergic influences on sound-induced seizures. 610 28

A growing body of evidence supports a pathophysiological role for norepinephrine (NE) and serotonin in the regulation of seizures in the genetically epilepsy-prone rat (GEPR). Other evidence indicates that gamma-aminobutyric acid (GABA) and taurine may also participate in the seizure regulation process. Innate deficits in NE and serotonin appear to be causes of the genetically determined seizure-prone states of the GEPR, whereas abnormalities in GABAergic systems and taurine metabolism may represent inadequate attempts of the central nervous system to compensate for the seizure-prone state in these rats. In audiogenic seizure-susceptible (AGS) mice, evidence suggests a role for dopamine as well as GABA and possibly serotonin. NE may contribute to the regulation of seizures in AGS mice, but consistent evidence for a primary role for this monoamine is lacking. It is suggested that there is no single common neurotransmitter abnormality underlying genetic seizure disorders in humans or other animals and that the GEPR and the AGS mouse may both serve as good models for study of the neurochemical abnormalities that underlie the different human epilepsies.
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PMID:Neurotransmitter abnormalities in genetically epileptic rodents. 614 25


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