Modeling of Focal Seizures with Automatisms in Rats with Pendulum Movements

Phenotypical study was carried out in rats with pendulum movements. The animals exhibited a high level of abortive seizures in response to audiogenic stimuli and longer postictal catalepsy in comparison with those in Wistar population. Seizure severity positively correlated with the duration of poststimulus catalepsy (r=0.90). High aggressiveness towards humans, the absence of BP elevation in stress, lower body weights, and lower weights of the kidneys and spleen in PM rats are considered concomitant traits. Correlations were detected between startle-1 and BP in rats with pendulum movements (r=0.70) and between startle-10 and BP in narcotized Wistar rats (r=-0.0.71). The newly described signs in rats with pendulum movements did not contradict the signs of the focal seizure model with typical automatisms in humans.

SPERM QUALITY IN RATS PREDISPOSED TO THE MANIFESTATION OF CATATONIC REACTIONS

Catatonia is a psychopathological syndrome displayed as a motor disorder. Catatonia is a sign of many menthal disorders, particularly schizophrenia and depression, with a wide disrtibution in the human population. The GC (“genetic” and “catatonia”) rat strain was obtained from the Wistar rat strain by a long selection (78 generations) for the catatonic type of reaction and is a model of schizophrenic and depressive disorders in humans. It is known that selection for behavior including catatonic reactions results in neuroendocrine, reproductive and morphological changes in animals. However, the influence of selection for a catatonic reaction on the spermatogenic function of testes had not been studied. The aim of this study was to conduct a comparative investigation of sperm quality in rats of the GC and the Wistar strain. The epididymal sperm parameters (sperm count, sperm motility, sperm morphology) were measured, and body, testes and epididymal weight were determined at puberty (50 day of life) and at adulthood (90 day of life). The litter size of the GC and Wistar rats was determined. It was found that adult GC rats had a lower sperm count, sperm motility, testis weight, epydidymal weight and litter size compared to adult Wistar rats. However, at puberty, GC rats had a higher sperm count than the Wistar strain. Interstrain differences in sperm morphology were not found. It has been assumed that the changes of spermatogenic parameters in response to selection for catatonia are caused by changing the ontogenic pattern of testosterone secretion. In conclusion, the hereditary predisposition to catatonic reaction is associated with impaired sperm parameters in adult rats that reduces their chance to reproduction. The GC rat strain can be a perspective model for investigation of the relationship between the hereditary predisposition to catatonia and spermatogenesis

INTERSTRAIN DIFFERENCES IN EMOTIONAL AND WEIGHT INDICES IN GC RATS WITH CATATONIC RESPONSE AND WISTAR RATS

In selecting rats for behavior, we observe a direct natural effect and affect the nonspecific stress function. In this process, new behavioral phenotypes appear in the strain under selection. They differ from the selected forms in the selection criterion. In the GC strain, a large proportion of the so-called nervous rats emerge. The criterion presumes the selection for the long cataleptic freezing character, whereas the nervous rats display elevated motor excitement: running, jumping, and vocalization. The main purpose of our study was to assess phenotypic indices in GC rats (abbreviated from genetic and catatonia) and recognize principal components of variability for emotional and weight indices. Rats of the ancestral Wistar population were taken as control. The following indices were measured: time of cataleptic freezing, excitement level, blood pressure, acoustic startle response, seizure  activity, and weights of the heart, kidneys, adrenals, and spleen. Multivariate analysis methods were applied: factor analysis and principal component analysis. We confirmed the inclination of GC rats of the generation studied to freezing in quiet surrounding and after a strong acoustic sti - mulus. More pronounced startle responses,  moderate hypertension, and larger weights of the heart and adrenals were noted. Two principal variability components were recognized: startle amplitude (PC1) and morphofunctional variability (PC2). The figure shows different locations of Wistar and GC individuals in principal component coordinates. The principal component method confirmed the genetic relationship between the startle and nervousness responses. It was shown that in PC2 the indices of heart, kidney, adrenal, and spleen weight exert negative effects, whereas the effects of startle and nervousness were positive. In the same component, an increase in the startle and nervousness responses positively correlates with the relative weights of the heart and adrenals. Differences in the directions of the contributions to the second component of morphofunctional variability are discussed.

[Comparative analysis of imipramine intake reactions in catatonic and wistar rats]

Chronic imipramine intake (7.5 mg/kg) leads to the stable decrease of excitable reactions to sound stimulant in Wistar rats and induced phase behavioral response in catatonic GC rats. Increased noradrenaline level in frontal cortex and striatum in Wistar animals was shown, whereas it didn't reveal noradrenaline level differences in any brain structures in GC rats. The higher blood corticosterone concentration was decreased under antidepressant reaction in GC rats. Differences between intact GC animals were found out: reduced triglyceride level, lesser body weight, and greater weight index of adrenals in comparison with Wistar rats. Various mechanisms of imipramine action in two rat strains were shown: influence on adrenergic brain system, taking part in the control of exiting behavior in Wistar rats and reaction in adrenals in GC rats.

[Selection for catatonic reaction in rats: a study of interstrain differences by magnetic resonance imaging]

Brain studies by magnetic resonance imaging, angiography, and spectroscopy have been performed with rat strains Wistar, GC (genetic and catatonia), and PM+ (pendulum movements). Both GC and PM+ rats show similar deviations from the ancestral Wistar population in having smaller areas of the right striatum (coronal slice). The anterior horns of lateral ventricles in GC rats are smaller than in the control strain. The maximum blood flow velocity in the common carotid arteries of PM+ rats is greater. The GC and PM+ strains differ in myo-inositol level in the hippocampus. The PM+ strain is characterized by a lower taurine level in the hippocampus, which may be one of the participants regulated the predisposition to audiogenic seizures.

[The increase in the proportion of nervous animals bred for catatonia: the participation of central adrenoreceptors in catatonic reactions]

Using a large amount of breeding material, the idea of D. K. Belyaev on the role of selection in the appearance of new behavioral and neuronal forms was confirmed. Experiments were performed using rats of the GC (genetics + catatonia) strain, which are prone to passive defensive reactions of cataleptic freezing. At the current breeding stage, elevation of the proportion of so-called nervous animals was demonstrated, both with respect to the expression of such reactions and their frequency. At this breeding stage, in the brains of GC rats, the mRNA levels of alpha1A- and alpha2A-adrenoreceptor genes were determined. A decrease of alpha1A-adrenoreceptor gene expression in the midbrain and medulla oblongata, along with elevation of alpha2A-adrenoreceptor gene expression in the frontal cortex was observed. It was suggested that changes in the expression of alpha-adrenoreceptor genes could be caused by an increase in the proportion of nervous animals and could contribute to the akinetic behavioral component in GC rats.

[Behavioral characterictics of ISIAH rat strain]

This work was performed in hypertensive ISIAH and normotensive WAG rat strains. The latter was used as a control group. The general evaluation of behavior of the ISIAH and WAG rats tested in the open field, in the light-dark test, in the sound stress test, and in the fatigue test showed that the motor and exploratory activity provoked by an unfamiliar environment was much higher in the ISIAH rats as compared to the control WAG strain. Spontaneous locomotor activity of the ISIAH rats in the home cage was significantly lower as compared to the control WAG strain. This finding suggests that the ISIAH rats are hyperreactive in an novel environment. It is concluded that the hypertensive ISIAH rats are significantly different from the control WAG rats not only in the arterial blood pressure level, but also in behavioral patterns.

Age-specific features of estrous cycles and folliculogenesis in GC female rats selected by catatonic reactivity

A decrease in the total count of follicles in the diestrus and proestrus and higher incidence of permanent estruses were found in 3-month-old females of the catatonic GC rat strain in comparison with Wistar females (control). At the age of 6-12 months, GC females had lower incidence of long estrus and diestrus. The estrous cycle of GC females was shorter than of Wistar rats. With aging (at the age of 18 months), the counts of growing and maturing follicles significantly decreased. Higher counts of growing single-layer and bilayer follicles were found in 18-month-old GC females. Differences in the length of estrus and diestrus and in the incidence of abnormal phases in the two strains also disappeared at this age. Selection by high catatonic reactivity was associated with a decrease in body weight.

Effect of imipramine on nerve excitability in GC rats

Imipramine test (7.5 mg/kg) revealed a persistent positive reaction of Wistar rats, which manifested in reduced excitability of animals. Oral administration of imipramine solution was followed by unstable behavioral reactions in GC rats. Norepinephrine concentration in the cortical and limbic regions of these animals remained unchanged, while plasma corticosterone concentration decreased to the control level and did not differ from that in Wistar rats. Our results indicate that imipramine has a modulatory effect on destabilization of the adaptive system in catatonic GC rats.

[Learning of rats predisposed to catalepsy in Morris water test]

It was shown that GC rats predisposed to catalepsy do not differ from Wistar rats in success rate or latency (time of finding of the hidden escape platform) in the Morris water test. However, unlike Wistar, GC rats are inclined to passive drift and longer floating episodes. Rats of the MD+ strain predisposed to hyperkinesis in the form of horizontal pendulum-like movements of the head and upper limb girdle show longer latency and lower rate of successful trials than Wistar or MD-, rats selected for absence of the pendulum-like movements.

Monoamines and sexual function in rats bred for increased catatonic reactivity

Body weight, ovary and uterus weight, the nature of estral cycles, and hypothalamus dopamine and noradrenaline levels and plasma testosterone levels were studied in female GC rats, bred for increased catatonic reactivity, at different stages of the estral cycle (estrus, proestrus). The outbred Wistar strain served as controls. On the background of decreased body weight, GC females showed impairments to the morphological cyclical changes in the ovaries and uterus, with a reduction in ovary weight in diestrus (p < 0.01) and a smaller estrogen-dependent increase in uterus weight in estrus as compared with Wistar females. On the background of decreases in dopamine and noradrenaline contents in the hypothalamus, GC rats showed higher levels of these monoamines in estrus and lower levels in diestrus. Plasma testosterone levels in female GC rats were higher in diestrus than in estrus and in Wistar rats.

Genetic catalepsy and ultralow dose antibodies to S-100B antigen

We studied consumption of 20% sucrose solution by rats genetically predisposed to catalepsy (GC strain) during training. The consumption of sucrose solution by GC rats was lower in comparison to that in Wistar rats. "Potentiated" antibodies to S-100B antigen administered orally after training sessions increased the number and duration of subsequent contacts of rats with sucrose solution.

[Monoamines and function of the ovaries in rats selected for elevated catatonic reactivity]

Levels of dopamine (DOPA), noradrenalin (NA), and serotonin in hypothalamus and function of ovaries (folliculogenesis) were studied at various estrous cycle stages of the rat GK line selected for elevated catatonia. The control was the outbred Wistar line. Selection for elevated catatonia led to a decrease of the number of all cell types in GK ovaries in diestrus and proestrus. In estrus of the GK females, on the contrary, there was a tendency for an increase of the number of the growing follicles as compared with Wistar females. On the background of a decrease of the DOPA and NA content in hypothalamus of the GK line rats, the higher catecholamine level was observed in estrus and the lower--in diestrus. Thus, selection for manifestation of the excessive protective catatonical type of reaction in the form of an increase of duration and intensity of freezing involves the monoaminergic brain system and leads to delay of folliculogenesis that is the key factor in regulation of fertility.

[Monoamines and reproductive function of rats selected for strengthening of catatonia response]

Weights of the body, ovaries, and uterus; estrous cycles and the contents of dopamine (DA) and norepinephrine (NE) in the hypothalami, and testosterone in blood plasma of GC females were studied at various estrous stages (diestrus and estrus). The outbred Wistar line was used as a control. In addition to reduced body weight in GC females, we observed disturbed morphological cyclic linkages between the ovaries and uterus: ovary weight reduction in diestrus (p < 0.01) and lower estrogen-related increase in uterus weight in estrus in GC females in comparison with Wistar ones. While the contents of DA and NE in GC hypothalami were reduced, the levels of these monoamines were high in estrus and low in diestrus. Testosterone levels in GC female plasma in diestrus were higher than in estrus or in Wistar rats.

[Some neuroendocrinological changes in rats of cataleptic strain GC. Influences of ontogenesis and generation of breeding]

The content of biogenic amines: dopamine, noradrenaline and serotonine, in rats of cataleptic strain GC as compared with the control strain Wistar at the age of 1 and 5 months is decreased, the maximal decrease being found in the so-called "nervous" animals. The aldosterone content was decreased at 5 month age in the GC rats. The testosterone content at the age of 1 month in GC rats does not differ from that in Wistar rats, but at the age of 5 months it was decreased as compared to Wistar, the maximal decrease being found again in "nervous" GC rats. The data obtained point to peculiarities of ontogenetic regulation and to commonness of mechanisms of catalepsy and "nervousness" in GC rats.

[Dual manifestation of catatonic reaction in rats]

Results of genetic, neurophysiological, neurochemical and pharmacological suggest that the cataleptic freezing and "nervousness" observed in the cataleptic rat strain GC have a common mechanism. There seems to be a physiological factor causing catalepsy, upon reaching a certain level of intensity, to be transformed into "nervousness", which is observed both at different period and/or moment of individual life and in the processes of breeding the strain for predisposition to catalepsy.

Diurnal variations in lymphocyte subpopulations in lymphoid organs of rats with genetic catalepsy and Wistar rats

Parameters of the immune status of the thymus and spleen in rats with genetic catalepsy were lower compared to those in Wistar rats. Diurnal variations in cell subpopulations of lymphoid organs were different in animals of these strains. Behavioral characteristics and neuroendocrine state in rats with genetic catalepsy were associated with specific changes in the immune system and neuroimmune interactions.

Chronic administration of imipramine decreases freezing time in rats genetically predisposed to catalepsy

The effects of acute and chronic imipramine treatment on the degree of catalepsy were compared in GC rats genetically predisposed to catalepsy. We recorded the time over which the rats remained in a vertical position they were placed. As differentiated from acute treatment, chronic administration of imipramine dose-dependently decreased the time of freezing in GC rats.

[Catatonia or depression: the GC rat strain as an animal model of psychopathology]

The utility of "incomplete" genetic animal models of human diseases, in particular, psychoses, is discussed. The GC rat strain selected for predisposition to cataleptic reactions is described. It is shown that in many of their characteristics, GC rats are similar to schizophrenic and depressive patients. A possibility that akinetic catatonic states and depressions, hyperkinetic catatonic states and mania share common mechanisms is discussed. It is hypothesized that the GC strain may be an incomplete model of the common genetic and pathogenetic core of schizophrenic substuporous states and depression, which suggests the importance of returning to the issue of a unitary psychosis (Einheitpsychosis).

Correlation Between Cataleptic Freezing and Prepulse Inhibition of the Startle Reflex in Rats

GC rats, bred for a predisposition to cataleptic freezing, were found to show a significant negative correlation between the duration of freezing and the level of prepulse inhibition of the startle reflex. In addition, a group of GC rats characterized by increased "nervousness" also showed a negative correlation between the duration of freezing and the extent of habituation of the startle reflex. These correlations were not seen in Wistar rats. Since decreases in the level of prepulse inhibition and habituation of the startle reflex are regarded as characteristic of schizophrenia, it is suggested that cataleptic freezing in GC rats might be used as a model of schizophrenic pyschopathology.

[Bipolar manifestation of cataleptic reactions in rats]

Selection of GC rats for the predisposition to cataleptic freezing has increased not only the frequency, intensity, and duration of freezing, but also the proportion of irritable or "nervous" rats with enhanced anxiety, defensive behavior with vocalization, jerky running, and jumpiness. An increased amplitude of the startle reflex is a correlate of this "nervousness." The results of the comparison of some behavioral characters in the nervous and freezing GC rats, as well as in F1 and F2 offspring from homogeneous crosses between nervous and freezing GC rats suggest that cataleptic freezing and nervousness are two poles of the same bipolar catatonic reaction. They have a common mechanism, with the alternative or preferential expression of one particular form of the reaction is determined by the external and internal environments or the set of modifier genes in the given individual.

Components of early maternal environment affecting the predisposition to catalepsy

Reciprocal pup substitution (cross-fostering) in cataleptic GC (designated so by the initials of words "genetic" and "catalepsy") and control Wistar females resulted in attenuation of cataleptic predisposition in GC rats fostered by Wistar foster-mothers. The latter demonstrate a more intense maternal care than GC females. There was a significant negative correlation between the frequency of mother staying in nest and the duration of pinch-induced catalepsy in pups fostered by her. In the home-cage retrieval test, the females of the strains compared showed a significant dependence of the latencies of approach to, and retrieval of, pups on their own and the pups' genotype.

[Behavioral and physiological characteristics of nonagouti mutation in gray rats during selection for aggressiveness]

The goal of this work was to find out to which degree the black coat color mutation nonagouti that appears in wild Norway rat in the course of breeding for the maintenance and enhancement of aggressiveness towards a human affects selected and other behavioral traits as well as stress reactivity and brain neurochemistry. Nonagouti rats displayed increased emotionality in the open-field and forced-swimming tests as compared to agouti animals, whereas there were no differences in anxiety estimated in the elevated plus-maze. Neither were there any differences in glucocorticoid reactions to a combined stressful procedure such as forced swimming. The dopamine content in the frontal cortex and striatum and noradrenaline content in the frontal cortex were increased in black rats as compared to gray rats. The result suggest that the nonagouti mutation in gray aggressive rats enhances the effects of selection for aggressiveness on some behavioral traits and brain catecholamine level.

[Correlation between cataleptic freezing and prestimulation inhibition of the startle reflex in rats]

In rats of GC strain bred for predisdposition to cataleptic freezing, a significant negative correlation between the duration of freezing and the level of prepulse inhibition (PPI) of the startle reflex, has been found. Besides, in a group of GC rats specific by their "nervousness" and jumpiness, there was also a negative correlation between the duration of freezing and the habituation to the startle reflex. None of this correlation have been found in Wistar rats. Since impairment of the PPI and habituation of the startle reflex is considered to be characteristic of schizophrenia, it is believed than cataleptic freezing in the GC rats may be used as a model of schizophrenic psychopathology.

Effect of chronic administration of imipramine on 2A-serotonin receptor mRNA in brain cortex of rats predisposed and resistant to catalepsy

Rats selected by predisposition to catalepsy showed decreased level of 2A-serotonin receptor mRNA in the frontal cortex in comparison with Wistar rats (p<0.05). Chronic administration of tricyclic antidepressant imipramine hydrochloride 2-fold increased the content of receptor mRNA in genetically cataleptic rats (p<0.001) and did not change this parameter in Wistar rats. These results prompted us to revise current notion on the mechanisms of chronic effect of imipramine on 2A-serotonin receptors.

Effects of thyroid hormone deficiency on behavior in rat strains with different predisposition to catalepsy

The effects of thyroidectomy on anxiety-related behavior in the elevated plus-maze test, locomotor activity, and defecation in the open-field test and duration of cataleptic freezing were studied in rats of two strains differing in predisposition to catalepsy: cataleptic strain GC and its ancestor strain Wistar. Total thyroxine level was significantly decreased in control GC rats compared to that in control Wistar rats. Control Wistar and GC rats did not differ either in the percentages of open-arm entries or the time spent therein in the elevated plus-maze test or in defecation score in the open-field test. At the same time, control Wistar rats showed more locomotor activity compared to control GC rats in the open-field test. Thyroid hormone deficiency did not affect the percentages of open-arm entries and the time spent therein in the elevated plus-maze test as well as defecation score in both strains. Thyroidectomy did not alter significantly locomotor activity in Wistar rats, but produced a nearly twofold increase in locomotor activity in GC rats. The most important finding is that thyroidectomy significantly increased the expression of catalepsy in Wistar rats, which points to a role of thyroid hormones in the regulation of predisposition to cataleptic reaction.

[Effect of changes in the early maternal environment on predisposition to catalepsy in rats of different ages]

Reciprocal cross-fostering of control Wistar and catalepsy-prone GC rat pups resulted in a decrease in duration of cataleptic reactions of GC rats estimated at the age of two weeks, one month, and six months and a tendency to its decrease in Wistar rats at the age of one month. In-fostering did not exert this effect.

[Effect of cross-fostering on catalepsy and the brain monoamine level in rat offspring prone to catalepsy and in the control strain]

Duration of cataleptic reactions in male rats of Wistar and GC strains depended both on the genotype and on the type of rearing: it was longer in the GC rats than in the Wistar ones. In the GC males reared by Wistar foster mothers this parameter was smaller than in the control GC but higher than in Wistar rats. The NA content was significantly lower in the GC cortex, hypothalamus and striatum, and the level of serotonin and 5-HIAA was lower in cortex of the GC as compared with Wistar rats. The cross-fostering affected monoamine content in some brain structures. On the whole, serotonin, DA and NA systems of the GC rats proved to be more susceptible to stress caused by cross-fostering than those of the Wistar rats. The cross-fostering diminished interstrain differences in the NA level in cortex, striatum, and hypothalamus.

Thyroid hormone deficiency determines predisposition to catalepsy in rats

The role of thyroid hormones in predisposition to cataleptic reaction was investigated. GC rats with genetic predisposition to catalepsy were characterized by decreased serum thyroxin content in comparison with Wistar rats. Thyroidectomy even more reduced the blood concentration of thyroxin in GC rats 30 days postoperation and augmented predisposition to catalepsy in both rat strains.

Some physiological manifestations of the activity of the gene controlling the predisposition to pendulum-like movements in rats

The physiological actions of the gene controlling the predisposition to stereotypic hyperkinesia in the form of pendulum-like movements (PM) and, probably, a form of spontaneous nystagmus in rats with albinism are manifest as a number of behavioral characteristics (total motor activity, emotionality, startle reflex intensity, sensitivity to serotonin 5-HT2 receptors as assessed in terms of the intensity of head twitching, and predisposition to cataleptic responses). A number of parameters showed differences between hybrids of gray handling-tolerant rats and carriers of the PM gene on the one hand, and between gray rats and animals not carrying the PM gene on the other. Some behavioral characteristics of rats with PM were closer to those of Wistar rats than to those of rats without PM. This, as well as the high frequency of PM in Wistar rats, indicates that the gene responsible for the manifestations of PM is not pathological, but controls a variety of adaptive features of the nervous system. The interaction between PM and the predisposition to catalepsy is biphasic in nature and is described by a curve in the form of an inverted U.

[Effect of cross-fostering on various physiological and behavioral features in Wistar and genetically cataleptic rats]

In the GC rats reared by their natural mothers the plasma corticosterone concentration and open field locomotion were lower than in Wistar rats whereas the startle-reflex amplitude was higher. Cross-fostering did not affect the plasma corticosterone concentration or the startle-reflex amplitude. A negative correlation between these parameters was found. An open field test yielded lower results in Wistar rats reared by foster mothers belonging to the GC strain whereas the reverse cross-fostering did not affect the locomotion in GC rats. The data suggest that fostering affects the open field behaviour whereas cross-fostering effects depend on the genotype of fostered litter.