Development of susceptibility to audiogenic seizures in DBA/2J and Rb mice: toward a systematic nomenclature of audiogenic seizure levels

A systematic nomenclature of levels of audiogenic seizures has been proposed and applied to describe the developmental changes in susceptibility in Rb-1, Rb-2 and DBA/2J mice.

The effect of naloxone on audiogenic seizures

The severity of audiogenic seizures was increased in two strains of mice 5--10 min after naloxone (2 or 4 mg/kg IP). This may indicate involvement of an endorphin or enkephalin in the modulation of reactivity.

Sources of energy for the brain and physical dependence on ethanol

This paper describes a proposed biochemical mechanism to account for physical dependence on ethanol. Long-term exposure to a continuous and plentiful supply of ethanol-derived hydrogens in NADH and ethanol-derived acetyl-CoA (AcCoA) may lead to a decreased rate of production of endogenous hydrogens in NADH and endogenous AcCoA in compensation. It is proposed that physical dependence on ethanol occurs when ketolytic- and glycolytic-based NADH and AcCoA synthetic rates fall below the rate of utilization by the brain; the brain then "depends" on alcohol-derived NADH and AcCoA for normal function.

Sources of energy for the brain and susceptibility to audiogenic seizures

The onset of susceptibility to audiogenic seizures (AGS) coincides with the draining of the ear canal at about 14 to 16 days of age. This is also when the mouse brain has almost attained its maximal size and weight, and also about the time of weaning from the dam's high-fat milk to the beginning of dietary self-sufficiency. During suckling, the brain is primarily dependent on ketone-body utilization as a source for brain energy; weaned mice use glucose. It is suggested that in AGS-prone mice, there may be a developmental lag in the onset of a sufficient rate of glycolysis in brain to provide adequate immediately available energy reserves to last through a brief period of an external-stimulus-induced large energy expediture until energy repletion processes can begin. As a results, ATP levels might fall below an hypothesized lower limit to subserve organized neural activity in some inhibitory area of the brain, resulting in the onset of an AGS.

Time course of protection from audiogenic seizures by glucose and insulin in audiogenically primed C57BL/6J mice

Glucose and insulin injections both decrease seizure susceptibility in C57BL/6J mice subjected to audiogenic priming at 16 days of age and tested at 21 days of age. These data support an hypothesis of defect in immediately available energy reserves in brains of audiogenic seizure prone mice.

Audiogenic seizures and brain extracts: enhancement by extracts from C57BL/6J mice subjected to audiogenic priming

Donor C57BL/6J mice were given audiogenic priming (AP) by exposure to noise at 16 days of age (To) and sacrificed at intervals from 1 hr to 18 days therafter. Brains from AP and littermate non-AP mice were extracted in 1 M acetic acid, and passed through a filter with a nominal mol. wt. cutoff of 10,000 daltons. The filtrates were lyophilized and resuspended in H2O (0.1 ml/brain). Recipient C57BL/6J mice were also exposed to 30 sec of 127 +/- 2 dBA at 16 days of age, and injected IP with one brain-equivalent of extracts from either AP or non-AP donors immediately therafter. All recipients were tested for convulsability at 18 days of age. There were no differences in audiogenic convulsion rates between groups given AP or non-AP extracts from donors sacrificed 1 to 4 hr after To. Recipient convulsion rates were higher in AP relative to non-AP extract-injected mice whenAP donors were sacrificed 1 to 18 days after To. The extract taken from donors 1 day after To appears more potent than extract taken either before or later.

Effects of stimulus intensity and stimulus duration during acoustic priming on audiogenic seizures in C57BL/6J mice

The effects of stimulus intensity and stimulus duration were examined in C57BL/6J mice not susceptible to audiogenic seizures (AGS) on the 1st exposure to an acoustic stimulus. Two experiments were performed. In the 1st, 16-day-old mice were exposed to 108, 112, 120, or 127 dB for 60 sec. Mice were then tested for susceptibility to AGS at varying ages thereafter. Increasing intensity of noise during priming resulted in heightened peak seizure risk, and extended duration of peak seizure risk, and a prolonged time of seizure risk. In the 2nd experiment, mice were exposed for 5, 15, 30, or 60 sec to 127 dB of noise. Five seconds of noise was barely sufficient to induce later susceptibility to AGS. Increasing stimulus duration from 15 to 30 to 60 sec resulted in increasing seizure risk and duration of peak risk period.

Audiogenic priming in DBA/2J and C57BL/6J mice: interactions among age, prime-to-test interval and index of seizure

C57BL/6J mice, not susceptible to audiogenic seizures (AGS) on the 1st exposure to an acoustic stimulus, were exposed to the acoustic stimulus for 1 min and then tested at some later date (acoustic priming). They were first exposed at either 8, 16, 19, 22, or 28 days of age, and then tested for AGS 2-16 days after priming. DBA/2J mice, susceptible to AGS on the 1st exposure to intense noise, were exposed to the acoustic stimulus at 26 days of age, and then again 2-14 days later. Data indicate that the incidence of AGS upon the 2nd exposure to the acoustic stimulus is a function of age at priming, the prime-to-test interval in days, and the index of seizures. In the case of DBA mice, later effects are also dependent on the initial level of seizure.

The effects of parity, litter size, season, and breeding protocol on the number of DBA/2J Ten mice available for weaning

Data on the reproductive behavior of DBA/2J Ten mice, collected from October 1970 through March 1973 and utilizing a 2-female, 1-male breeding system, with the mice remaining together throughout their reproductive life indicates: a) Litter size tends to increase through the fourth litter, the first litter being much smaller than successive litters; b) Survival rates of litters with 2--4 pups increase with successive deliveries; c) Survival rates of litters with 5--9 pups are approximately the same regardless of parity; d) There is a circannual rhythm in the number of pups available for weaning da 21, which is attributable to changes in postnatal viability. Data collected using a breeding pen system, with isolation of females pre- and post-delivery (March 1973 to March 1974) indicates: a) There is a reduction in live litter sizes in later litters with this system; b) There is a large reduction in the proportion of pups surviving to weaning with this system when compared with the other breeding system.