Stereotyped behavior in the ontogeny of rats

The ontogenetic development of stereotyped behavior induced by activation of dopamine D1 and D2 receptors with apomorphine was studied in rat pups (1st month of life) and adult rats (2nd–12th months of life). Stereotyped sniffing and licking movements developed not simultaneously under the influence of apomorphine. Apomorphine-induced sniffing hyperactivity was observed in newborn animals, but disappeared after eye opening (day 18 of life). Stereotyped licking movements (long-term intense licking of the wall of the actograph) induced by activation of dopamine D2 receptors with apomorphine were revealed in rat pups on the 4th week of life. The duration of these movements in rats was maximum by the 9th month of life. The dynamics of stereotyped behavior probably reflects the non-simultaneous formation and development of dopamine D1 and D2 receptors in the ventrolateral striatum during the ontogeny of rats. __________ Translated from Byulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 144, No. 9, pp. 325–327, September, 2007     

The ontogeny of anxiety-like behavior in rats from adolescence to adulthood

In human beings, susceptibility to anxiety disorders can be relatively high during adolescence. Understanding the ontogeny of anxiety-like behavior in laboratory rodents has implications for developing anxiolytic drugs that are suitable for this age group. Given the dearth of information about adolescent rodents, this study examined the response of both male and female adolescent, late adolescent, young adult, and older adult rats to three tests of anxiety-like behavior: the emergence test (ET), open field (OF), and elevated plus-maze (EPM). The results showed that adolescent rats exhibited a higher anxiety-like response than adults on each test; the amount of locomotion in the OF and percentage of time spent on the open arms of the EPM increased across the age groups, while older adult rats made the fewest start box re-entries in the ET. These results support the hypothesis that adolescent rats have a more pronounced response to stressors than do adults.     

The ontogeny of play in rats

Play behavior, as indicated by frequency and duration of pinning behavior, was studied in young rats between 18 and 64 days of age. The incidence of play was markedly increased by social isolation. Play increased from 18–28 days of age, peaked between 32 and 40 days of age, and gradually declined thereafter. Animals developed stable “dominance hierarchies” during the course of testing so that one animal pinned the other on the average 70% of the time. Also, “dominant” animals exhibited the longer pin durations. The data indicate that social play can be efficiently studied in the laboratory rat and, further, that one function of play may be to establish stable social relationships.     

The ontogeny of exploratory behavior in male and female adolescent rats (Rattus norvegicus)

During adolescence, rats gain independence from their mothers and disperse from the natal burrow, with males typically dispersing further than females. We predicted that, if dispersal patterns are associated with responsiveness to novelty, exploratory behavior in novel environments would increase across adolescence, and males would explore more than females. Alternatively, females might explore more than males, if females are more motivated than males to learn about the immediate environment or if females have poorer spatial abilities than males. Twenty‐five male and 21 female rats were exposed to two novel environments (open field and elevated plus‐maze) during early, mid‐, or late adolescence. Total locomotion and amount of exploration directed towards aversive areas increased across adolescence, even when body weight was included as a covariate. Female adolescents locomoted more and spent more time exploring aversive areas than males. Developmental changes in neural function potentially underlie age and sex differences in exploratory behavior. © 2009 Wiley Periodicals, Inc. Dev Psychobiol 51: 513–520, 2009     

The ontogeny of salt preference in rats

Many mammals eat salt irrespective of need. This behavior, called salt preference or appetite, is studied primarily in adults. Little is known about its ontogeny. In these experiments, 3-18-day-old rat pups were offered saline, quinine, or ammonium chloride solutions by infusion through an anterior oral catheter, and intake was measured. At 6-18 days, pups showed the inverted U-shaped preference-aversion curve for NaCl that is characteristic of adult rats. Thus, rats express a preference for salt at a very early age. However, the curves were broader than the typical adult curve and were shifted along the concentration gradient in an age-related fashion. Consumption of quinine and ammonium chloride showed similar age-related changes. These changes may reflect the postnatal timing of the development of the rat gustatory system.     

Effect of endothelin-1 on DNA synthesis in the myocardium of albino rats during early postnatal ontogeny

Effect of intraperitoneal injection of endothelin-1 on DNA synthesis in the myocardium of newborn albino rats was studied by³H-thymidine autoradiography. Endothelin-1 injected in a single dose of 10 μg/kg stimulated proliferative processes: the index of labeled nuclei and labeling intensity increased. Repeated (5 times) administration of endothelin-1 in doses of 1 and 10 μg/kg increased labeling intensity, but did not change the index of labeled nuclei. The data suggest that endothelins, are involved in morphogenesis of the myocardium during the early postnatal ontogeny. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 130, No. 12, pp. 623–626, December, 2000     

Effect of cassava consumption on open-field behavior and brain neurotransmitters in albino rats

Diet exerts a critical influence on human biology and thus studies on the interrelationship of nutrition and behavior continues to be a major and important focus of research in the natural experimental sciences. Cassava is known to cause metabolic and neurological derangement on long-term consumption as a staple diet in the tropics. In this article we present the effects of cassava consumption on open-field behavior and catecholamine levels in the hypothalamus of albino rats. Cassava consumption for 30 days alters the emotional status of the rats, with changes in the basal neurotransmitter levels in the hypothalamus. The role of the cyanide (liberated from cassava) and protein deficiency (associated with cassava consumption) has been discussed.     

Sequence of centromere separation: Occurrence,possible significance,and control

This review describes the existence of a phenomenon, sequential separation of centromeres, in mitotic cells of various species including both animals and plants. Critical observations at metaanaphase show that the centromeres of chromosomes in a given genome do not separate into two sister units randomly, but that there is a genetically controlled, nonrandom, species-specific sequence which is independent of the length of the chromosome or the position of the centromere. A stricter control appears to exist for late-separating than for early-separating chromosomes. At early stages of metaanaphase several chromosomes initiate onset of separation simultaneously or in rapid succession, but late-separating chromosomes are better defined in their sequential position. The effect of Colcemid on the sequence of separation is minimal. It is proposed that aneuploidy in humans and other organisms may result from out-of-phase separation of a given chromosome. With the exception of chromosome No. 16, it appears that very early- or very late-separating centromeres are involved in human trisomies more often than those in between.Perhaps one function of centromeric heterochromatin is the control of centromere separation. The amount of such chromatin shows a positive correlation with the timing of separation of the centromeres. Superimposed upon this quantitative influence is the qualitative aspect, as discussed for various genomes. This suggestion explains a lack of extremely large quantities of heterochromatin near the centromere. Its existence in the form of homogeneously staining regions distal to the centromere, as in some cancer cells or in sex chromosomes, seemingly has no influence on the separation of centromeres.A brief discussion of centromere separation errors in human disease is provided, and suggestions for further studies are made.     

Transition from pup killing to parental behavior in male and virgin female albino rats

In the first part of this study, the effect of habituation to pups was examined in virgin female and male Sprague-Dawley rats that committed infanticide in a screening test. With repeated exposure to test pups (5-10 days old), the rats ceased to commit infanticide and came to behave parentally. Preexposure to inaccessible pups (confined inside wire-mesh baskets) did not accelerate the rate of disappearance of infanticide during subsequent contact with young, which suggests that pup killing is not a neophobic response to the novelty of young. In the second part of the study, three groups of infanticidal male Wistar rats were mated and tested for their responses towards unrelated pups after different intervals of cohabitation with their mates. The males continued to commit infanticide at the time that their mates were at midpregnancy or 24 hr before parturition, but males that cohabited with their mates till day 9 postpartum no longer attacked the young. Thus, the mother rat, presumably by means of postpartum aggression, renders her mate noninfanticidal, thereby reducing the likelihood of her offspring being harmed when she is away from the nest.     

Visceroceptive control of operant behavior in rats

The effect of non-contingent visceral stimulation as well as the possibility of the discrimination of non-painful gastrointestinal stimuli was examined in an operant situation in rats. The animals were submitted to surgery and prepared with chronic isolated intestinal loops, chronically implanted gastric electrodes or tubing in order to enable the administration of visceroceptive stimuli of different intensities in the course of an operant conditioning procedure. It was shown that visceral stimuli above the behavioral threshold level, those causing startle reactions, orienting or motor responses, result in differential effects. Thus the discrimination of the presence or of the absence of gastrointestinal stimulation can be demonstrated in rats using the operant conditioning technique.     

Stimulus control of behavior and limbic lesions in rats

Rats with hippocampal lesions or sham operations learned a tone discrimination significantly faster than rats with amygdala lesions. Relative tone generalization gradients were significantly steeper for the animals with hippocampal lesions than for the other two groups. Performance on a light discrimination by the animals with hippocampal lesions was impaired, compared to the sham animals, when the tone (former S+) was present but irrelevant. The behavior of the amygdala animals was interpreted as being due to an inability to inhibit responding. The behavior of the animals with hippocampal lesions was interpreted as being due to an inability to shift attention from one stimulus to another.     

The primary optical projection in albino and pigmented rats]

1. We have studied by silver degeneration methods in transversal and horizontal brain series the pathways and the terminal nuclei of the primary optic system in albino and pigmented rats. 2. About 90% of the retinal axons are crossing in the Chiasma opticum. Differences between albino and pigmented rats are small. At the level of the lateral geniculate body (l.g.b.) the axons ramify. One branch is going in the optic tract or in the transversalsystem to the pretectum and tectum. The other branch goes as a collateral in the longitudinal system of the dorsal l.g.b. and ends here. 3. The optic fibers project--especially contralateral--to the following nuclei: veutral l.g.b. (lateral half), dorsal l.g.b., nucleus of the optic tract, Nc. olivaris praetectalis, Ncc. praetectales anterior et posterior and superior colliculus (laminae I-III). In the nuclei of the pretectal region are ipsilateral only a few degenerating fibers. 4. Especially in the dorsal l.g.b. but also in the superior colliculus the pigmented rats show ipsilateral an larger retinal input. 5. The ipsilateral fibers project to a special region in the dorsal l.g.b. This region is also innervated by contralateral axons. 6. In both the albino and pigmented rats the dorsal l.g.b. shows no lamination in the cytoarchitectonical picture and the ipsi- and contralateral input regions overlap. Therefore in the rat we can not speak from a laminated dorsal l.g.b. We have here--prepoperantly functional caused--a simple form of l.g.b. 7. The accessory optic system is only decussated. It includes the Fasciculus inferior tr. opt. accessorius, who projects only and direct to the median terminal nucleus and the Fasciculus superior tr. opticus accessorius. The last goes off from the optic tract at the level of the pretectal region and innervates all the 3 accessory optic nuclei. 8. In a few preparates we found references for a direct retino-hypothalamic connection (Nc. suprachiasmaticus and Nc. arcuatus hypothalami).     

Mechanisms of onset of morphological changes in the CNS in unanesthetized albino rats cooled by various methods

Changes in temperature regulation were compared with morphological changes in various parts of the CNS of unanesthetized albino rats cooled by different methods. The role of afferent impulses from the cooled tissues and of thermoregulatory excitation of nervous structures in the genesis of morphological changes in neurons of the reticular formation, mammillary bodies, and spinal cord was established. Morphological changes in cortical neurons are evidently due to the direct action of cold on the brain.     

The possible participation of a dopaminergic system in mutilating behavior in rats with forelimb deafferentation

The role of sodium (Na) in stimulus-secretion coupling of adrenal medulla was investigated in primary culture of bovine adrenal medulla cells. In Na-free medium, the secretion of catecholamines and influx of 45Ca induced by carbachol were decreased to 30% and 18% of control responses, respectively. Carbachol induced secretion of catecholamines and influx of 45Ca were not inhibited by tetrodotoxin, a highly selective blocker of voltage dependent Na-channels. Carbachol caused a rapid influx of 22Na which was inhibited by hexamethonium but not by tetrodotoxin. Nicotine but not muscarine could be a substitute for carbachol and caused catecholamine secretion, 45Ca influx 22Na influx. Veratridine caused continuous secretion of catecholamines and influxes of 45Ca and 22Na which were blocked by tetrodotoxin. These results indicate that in cultured bovine adrenal medulla cells, stimulation of nicotinic receptor causes the influx of Na through receptor-mediated Na-channels but not through voltage-dependent Na-channels, and that influxed Na may facilitate the influx of Ca which triggers the secretory process. The sodium ion seems to be involved in the stimulus-secretion coupling evoked by physiological secretagogue in adrenal medulla.     

The anaphylactic reaction and tachyphylaxis to eggwhite in albino rats

Summary Anaphylactic shock in rats may be provoked by an initial intravenous injection of fresh eggwhite. Previous administration of cortisone or desoxycorticosterone reduces the animals' resistance to the initial eggwhite injection, while adrenalectomy sharply decreases it.Cortisone restores the resistance reduced by adrenalectomy, while DOCS produces no appreciable effect.Resistance to eggwhite is also decreased on the 25th day after hypophysectomy, although to a smaller extent than in adrenalectomy.Different doses of ACTH employed at various intervals had no visible compensatory effect.The condition of tachyphylaxis occurred after the first injection of egg white. Preliminary cortisone and DOCS administration more or less preserved the ability to produce a tachyphylactic response.Presented by Active Member of the AMN SSSR N. I. Sirotinin     

Neuroendocrine control of urine-marking behavior in male rats

Sexually experienced Wistar male rats were used to investigate (a) urine voiding in the presence of nearby estrous females and the control of such voiding by (b) steroid hormones and (c) peripheral nerves supplying the genitourinary system. The first experiment showed that males always have a low rate of urine voiding that is significantly increased when a receptive female is around. Thus, it is suggested that an airborne scent from the female stimulates the olfactory system of males, triggering urine emission to transmit sex-related messages, i.e., male rats display the well-known urine-marking behavior of mammals. The number of urine marks and sniffing to females decreased after castration, and were restored after exogenous treatment with testosterone or estradiol. The proposed hypothesis is that airborne scents from the female activate the aromatization process in nuclei of the olfactory pathway of the male, evoking a cascade of neuronal responses that finish in urine marking. Peripheral nerves supplying the genitourinary system are the viscerocutaneous branch of the pelvic nerve (Vc) and the hypogastric (Hg). Data showed that both nerves are important for the central control of urine storage and voiding. Transection of Vc almost blocked urine marking, while Hg lesion increased the number of marks. Thus, it is discussed that Vc is the most important nerve in charge of voiding the bladder, and that Hg is important for continence.     

The albino locus and locomotor behavior in the mouse: Studies using extended test intervals

The influence of albinism upon initial activity in novel surroundings was examined using coisogenic and congenic lines of mice. In comparison with those of previous studies, an extended test interval was used, and this modification produced significant main and interaction effects of the c locus upon activity for both lines. The present findings confirm and extend those of previous studies upon the depressant effects of albinism based upon coisogenic lines, and extend the findings to congenic lines as well.     

Huddling by rat pups: ontogeny of individual and group behavior

A full account of behavioral development in rats must include the ontogeny of both individual and group behavior. Most of our accumulated knowledge, however, pertains to individual ontogenesis. Group behavior and its development are readily seen in the huddling behavior of rat pups. A rat huddle is an entity with characteristics and capabilities distinct from those of the individuals that comprise it. The huddle is a natural context for acquiring olfactory preferences for species odors. Olfactory learning in a huddle involves thermal and tactile stimulation from the mother's body but, surprisingly, not the rewards of suckling or of milk transfer. Although there is complete developmental continuity of huddling behavior, the sensory controls of huddling change dramatically during the first 2 weeks of postnatal life. Huddling behavior is initially controlled by thermal cues ("physiological huddling") and then becomes dominated by olfactory stimuli ("filial huddling"). The complex group behavior of huddling was modeled successfully with computational methods. Group behavior emerges from individual interactions, guided entirely by rules of individual behavior (no rules for group behavior). Three simple rules of autonomous activity/inactivity can spawn the patterns of aggregon formation displayed by groups of 7-day-old pups, but not by 10-day-olds. The developmental change evident by Day 10 requires adding a rule by which each individual is affected by the activity state of adjacent pups. Group behavior responded to manipulations of central oxytocin on Day 10, but not on Day 7.