Prednisolone blocks extreme intermale social aggression in seizure-induced, brain-damaged rats: implications for the amygdaloid central nucleus, corticotrophin-releasing factor, and electrical seizures

Impairments in cognitive functions and emotional and social behaviors in a rat lithium-pilocarpine model of temporal lobe epilepsy

The aim of this study was to evaluate in detail behavioral patterns and comorbid disturbances in rats using the lithium-pilocarpine model. A comprehensive set of behavioral tests was used to investigate behavioral patterns, including the open field test, Morris water maze, Y-maze, fear conditioning, the elevated plus maze, the forced swimming test, and the resident-intruder paradigm. Motor and explorative activity, learning and memory, anxiety and depressive-like behavior, aggression, and communication were evaluated 8-15 d after pilocarpine-induced status epilepticus (SE) (latent phase of the model) and 41-53 d (chronic phase) after pilocarpine-induced SE. Increased motor activity and impaired memory function were the most noticeable behavioral modifications in the epileptic rats. Both the movement speed and distance traveled increased in the open field test in both the latent and chronic phases. Significant impairments were detected in short-and long-term spatial memory in the Morris water maze during the latent phase. Besides the alterations in spatial memory, behaviors indicative of short- and long-term fear-associated memory disturbances were observed in the fear conditioning test during the chronic phase of the model. In the resident-intruder paradigm, epileptic rats exhibited disturbed communicative behavior, with impaired social behaviors. In contrast, emotional disturbances were less prominent, with the rats exhibiting decreased anxiety. There were no changes in depressive-like behavior. The data suggest that the lithium-pilocarpine model of TLE in rodents is more useful for studies of comorbid disturbances in memory, hyperactivity, and social behavior than for research on psychoemotional impairments, such as anxiety and depression.

Association between Intermale Social Aggression and Cellular Density within the Central Amygdaloid Nucleus in Rats with Lithium/Pilocarpine-Induced Seizures

Aggressive behaviors (numbers of bites/hour) within groups ( ns = 8) of normal rats and rats in which seizures had been induced by a single systemic injection of lithium/pilocarpine were observed for 11 successive, 1-hr. periods. Mean numbers of neurons and glial cells were counted for 10 different nuclei of the amygdala for 16 different brains (8 control; 8 seizure). Although there was no significant difference found between rats with chronically induced seizures and controls for the numbers of neurons per area within the central medial amygdaloid nucleus, the neuronal density was correlated significantly (.92) with mean numbers of bites per hour for the chronically epileptic group only. The hypothesis that seizure-induced damage within proximal amygdaloid nuclei disinhibits the central nucleus and encourages aggression was supported.

Herbal treatment following post-seizure induction in rat by lithium pilocarpine:Scutellaria lateri?ora (Skullcap),Gelsemium sempervirens (Gelsemium) andDatura stramonium (Jimson Weed) may prevent development of spontaneous seizures

About 1 week after the induction of status epilepticus in male rats by a single systemic injection of lithium (3 mEq/kg) and pilocarpine (30 g/kg), rats were continuously administered one of three herbal treatments through the water supply for 30 days. A fourth group received colloidal minerals and diluted food grade hydrogen peroxide in tap water, while a fifth group of rats received only tap water (control). Herbal treatments were selected for their historical antiseizure activities and sedative actions on the nervous system. The numbers of spontaneous seizures per day during a 15 min observation interval were recorded for each rat during the treatment period and during an additional 30 days when only tap water was given. Rats that received a weak solution of the three herbal fluid extracts of Scutellaria lateri flora (Skullcap), Gelsemium sempervirens (Gelsemium) and Datura stramonium (Jimson Weed) displayed no seizures during treatment while all the other groups were not seizure-free. However, when this treatment was removed, the rats in this group displayed numbers of spontaneous seizures comparable to the controls. Although there is no proof that herbal remedies can control limbic or temporal lobe epilepsy, the results of this experiment strongly suggest that the appropriate combination of herbal compounds may be helpful as adjunctive interventions.

The neuromatrix and the epileptic brain: behavioral and learning preservation in limbic epileptic rats treated with ketamine but not acepromazine

Conceiving the organization of the brain as a "neuromatrix" could provide significant insights into how different injuries to the nervous system could result in very distinct changes in behavior. The use of different pharmacological treatments to combat the deleterious consequences of such injuries is common practice. However, such treatments may have the capacity to alter the configurations of various neuronal circuits that contribute to the "neuromatrix" by selectively preventing damage to some pathways while facilitating the spread of destruction along others. The choice of pharmacological treatment may have profound consequences on the recovery of normal functioning following injury. We examined the behavior of rats treated with one of two potentially neuroprotective agents, the N-methyl-D-aspartate antagonist ketamine and the atypical neuroleptic acepromazine, on seizures induced by lithium-pilocarpine. Rats treated with ketamine following seizure onset were virtually indistinguishable from nonepileptic controls on a variety of behavioral tasks that included tests on learning, memory, and anxiety. In contrast, acepromazine-treated rats showed marked deficits on all learning and behavioral measures tested. These results suggest that administration of ketamine relatively soon after the emergence of epilepsy can prevent many of the cognitive deficits that are commonly found in rats subjected to lithium-pilocarpine-induced seizures. Further clinical testing investigating ketamine as a potential adjunct treatment for epilepsy may be well warranted.

Glutamic acid decarboxylase (GAD65) immunoreactivity in brains of aggressive, adolescent anabolic steroid-treated hamsters

Chronic anabolic-androgenic steroid (AAS) treatment during adolescence facilitates offensive aggression in male Syrian hamsters (Mesocricetus auratus). The current study assessed whether adolescent AAS exposure influenced the immunohistochemical localization of glutamic acid decarboxylase (GAD65), the rate-limiting enzyme in the synthesis of gamma-aminobutyric acid (GABA), in areas of hamster brain implicated in aggressive behavior. Hamsters were administered high dose AAS throughout adolescence, scored for offensive aggression, and then examined for differences in GAD65 puncta to regions of the hamster brain important for aggression. When compared with control animals, aggressive AAS-treated hamsters showed significant increases in the area covered by GAD65 immunoreactive puncta in several of these aggression regions, including the anterior hypothalamus, ventrolateral hypothalamus, and medial amygdala. Conversely, aggressive AAS-treated hamsters showed a significant decrease in GAD65-ir puncta in the lateral septum when compared with oil-treated controls. However, no differences in GAD65 puncta were found in other aggression areas, such as the bed nucleus of the stria terminalis and central amygdala. Together, these results support a role for altered GAD65 synthesis and function in adolescent AAS-facilitated offensive aggression.

Agonistic behavior in groups of limbic epileptic male rats: pattern of brain damage and moderating effects from normal rats

Different ratios of normal male rats and male rats in which limbic seizures had been induced by a single systemic injection of lithium and pilocarpine were housed in groups of six. The group ratios ranged along the continuum from all normal rats to all experimental rats. The average numbers of episodes of boxing, biting and mounting--thrusting per rat per hour per group were recorded by direct observation (red light) for 1 h during the midscotophase. Groups that contained less than two normal rats exhibited significantly elevated amounts of agonistic (boxing, biting) behavior but not mounting behavior. Multiple regression analyses showed that combinations of neuronal loss within only two to three areas accommodated at least 50% of the variance in the numbers of these behaviors.

Synchronized feeding as a "conditioned stimulus" for overt seizures in chronically (limbic) epileptic rats: a model for "psychogenic seizures" with complex partial epilepsy

Chronic limbic epilepsy was induced in male albino rats by a single systemic injection of lithium (3 mEq/kg) and pilocarpine (30 mg/kg). During the subsequent months the numbers of spontaneous, paroxysmal stereotyped episodes (analogous to Racine stages 4 and 5) were monitored. The numbers of these "overt seizures" increased within 10 min of the daily presentation of a food stimulus even though food was available ad libitum. The majority of the paroxysmal, stereotyped behaviours occurred within 1 min of the stimulus presentation; they were attenuated by oral prednisolone. Three rats displayed evidence of "conditioned seizures" to specific stimuli. The results suggest that the display of these behaviours can be synchronized and learned in contexts that are associated with the release of CRF (corticotrophin releasing factor) and may involve the disinhibited activity within the central amygdaloid nucleus of these rats. Implications for the occurrence of psychogenic seizures in patients with complex partial (limbic) epilepsy are discussed.

Drug discovery and the intracellular receptor family

Drug discovery using intracellular receptors (IRs) as targets presents its own set of unique complications and advantages. The natural ligands for these receptors are, in many cases, already used as drugs. To effectively exploit these targets, newer molecules must have either increased receptor selectivity or increased tissue or gene selectivity to reduce side effects. The search for these molecules will yield new therapeutics as well as new insights into the mechanism of action of these receptors and their ligands.

Differential effects of low frequency, low intensity (<6 mG) nocturnal magnetic fields upon infiltration of mononuclear cells and numbers of mast cells in Lewis rat brains

Immediately after inoculation to induce experimental allergic encephalomyelitis, 64 female Lewis rats were exposed to either a reference condition (<10 nT) or to one of two frequencies (7 Hz, 40 Hz) of magnetic fields whose two intensities (either 50 nT or 500 nT) were amplitude-modulated for 6 min once per hour between midnight and 8 h for 15 nights. Rats that had been exposed to the 7 Hz, low intensity fields displayed fewer numbers of foci of infiltrations of mononuclear cells compared to all other groups that did not differ significantly from each other. Rats exposed to the 5 mG (500 nT), 40 Hz magnetic fields displayed more foci in the right thalamus while those exposed to the 5 mG, 7 Hz fields displayed more foci in the left thalamus. Numbers of mast cells within the thalamus were also affected by the treatments. These results suggest that weak magnetic fields can affect the infiltration of immunologically responsive cells and the presence of mast cells in brain parenchyma. Implications for the potential etiology of 'electromagnetic sensitivity' symptoms are discussed.

Geomagnetic variables and behavior: LXXXIII. Increased geomagnetic activity and group aggression in chronic limbic epileptic male rats

PX / PPseparate experiments the daily intragroup aggression was IC SYSTEM / * PPo different measures for male rats with limbic epilepsy ESSION / * PXre were statistically positive associations of moderate strength (rs about .50) for the frequency with severity of intermale aggression and daily geomagnetic activity. The intense aggression was most evident when the daily aa values for the northern hemisphere, one measure of daily global geomagnetic activity, exceeded 40 nT. Implications for homologous behaviors for human beings, as a species, are suggested.

Long-term consequences of subtle stimuli during the first twenty-four hours of seizure-induced brain injury

Chronically epileptic (induced by a single systemic injection of lithium and pilocarpine about 30 days before the experiment began) male rats were trained within a radial maze while they were administered either GABA-pentin (Neurontin), or prednisolone or given no treatment. There was no significant improvement in learning or memory between the groups. Numbers of trials per day were positively correlated with the time required to display the overt stereotyped forelimb clonus after the single pilocarpine injection. The numbers of correct trials completed during the first few days of acquisition were significantly greater for the rats that had receive weak (1 microT) complex, pulsed magnetic fields over the right hemisphere during the first 24 hr. after seizure induction than for those who received the same field over the left hemisphere or that had been exposed to reference conditions. Implications of the enhanced sensitivity of limbic neurons to subtle electromagnetic interaction during electrical lability are discussed.