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Developing Rats (developing + rat)

Distribution by Scientific Domains
Medical Sciences40%
Life Sciences40%

Terms modified by Developing Rats

  • developing rat brain
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    Selected Abstracts

    Thyroxine Modulates Corticotropin-Releasing Factor but not Arginine Vasopressin Gene Expression in the Hypothalamic Paraventricular Nucleus of the Developing Rat

    JOURNAL OF NEUROENDOCRINOLOGY, Issue 8 2000
    N. Dakine
    Neonatal rats were daily injected with 100 ,g/kg T4 and killed at 4, 8 or 15 days. Circulating corticosterone and corticosteroid binding globulin concentrations increased in 8- and 15-day-old rats after T4 treatment. Plasma adrenocorticotropic hormone (ACTH) concentrations, pituitary ACTH content and pro-opiomelanocortin mRNA expression were unaffected in T4 -treated rats. T4 treatment induced an increase in corticotropin-releasing factor (CRF) mRNA expression in the whole population of CRF synthesizing cells of the paraventricular nucleus (PVN) that became significant at day 8 and disappeared at day 15. Double labelling in situ hybridization revealed that CRF gene expression in the CRF+/arginine vasopressin (AVP)+ subpopulation was increased at days 4 and 8 and decreased at day 15. CRF immunoreactivity in the zona externa of the median eminence increased with age but was not affected by the experimental hyperthyroidism. The degree of CRF and AVP colocalization, the concentration of AVP mRNA in the parvo and magnocellular cell bodies of the PVN and the density of immunoreactive AVP in the zona interna or zona externa of the median eminence did not change after T4 treatment. Our data demonstrate that experimental hyperthyroidism accelerates the maturation of hypothalamic CRF gene expression, including in particular in the CRF+/AVP+ subpopulation, during the stress hyporesponsive period. These observations suggest that the physiological peak of plasma thyroxine that occurs between days 8,12 may participate in the maturation of hypothalamic CRF cells. [source]

    Anticonvulsant Action of Topiramate Against Motor Seizures in Developing Rats

    EPILEPSIA, Issue 10 2000
    Renata Haugvicová
    Summary Purpose: To study the anticonvulsant action of topiramate (TPM) in developing rats. Methods: Motor seizures were elicited by administering pentylenetetrazol (100 mg/kg subcutaneously) in five age groups of Wistar rats (7, 12, 18, 25, and 90 days old). TPM was administered intraperitoneally in doses from 10 to 640 mg/kg 2 hours before pentylenetetrazol. The time course of TPM action was studied in 12- and 25-day-oId rats up to 24 hours after the 160-mg/kg dose, and the incidence and pattern of seizures were evaluated. Results: TPM did not influence minimal seizures (clonus of forelimb and head muscles with preserved righting ability). Generalized tonic-clonic seizures, however, were reliably changed at all developmental stages studied. The tonic phase was suppressed so that the majority of animals exhibited generalized clonic seizures (with a loss of righting reflexes). In addition, the incidence of generalized seizures was decreased after the 20-, 40-, and 80-mg/kg doses in the 7-day-old rat pups. The specific suppression of the tonic phase of generalized seizures was observed up to 12 hours in the 12-day-old rat pups. The same result was obtained over 6 hours after TPM administration in the 25-day-old animals, and with longer intervals the incidence of generalized seizures decreased in this age group. Conclusions: TPM exhibits stable anticonvulsant action against the tonic phase of generalized tonic-clonic seizures throughout development. In addition, it suppresses all phases of generalized seizures in 7-day-old rats. The anticonvulsant action of TPM lasted longer in 25-day-old than in 12-day-old rats. The two actions of TPM might be ascribed to two different mechanisms of action. [source]

    Effect of Ganaxolone on Flurothyl Seizures in Developing Rats

    EPILEPSIA, Issue 7 2000
    a Liptáková
    Summary: Purpose: To determine the effects of a newly synthesized epalon, ganaxolone (GNX), on primarily generalized seizures in rats of various ages during development. Epalons are classified as neuroactive steroids that interact at unique site of the GABAA receptor-Cl, channel complex in the central nervous system. Methods: Sprague-Dawley male rats were used at 9, 15, 30, and 60 postnatal days (PN). GNX dissolved in 2-hydroxypropyl-,-cyclodextrine was administered intraperitoneally in different doses at various time points before flurothyl testing. The incidence and threshold of clonic and tonic-clonic flurothyl seizures were evaluated. Behavioral changes were also assessed. Results: In all age groups, the effects of GNX were dose dependent and more prominent 10 min after its administration. In PN 60 and PN 30 rats, GNX had dose-dependent anticon-vulsant effects; tonic-clonic seizures were more sensitive to GNX treatment than clonic seizures. In PN 15 and PN 9 rats, GNX demonstrated dose- and time-dependent anticonvulsant effects against both types of flurothyl-induced seizures. GNX was more effective in PN 15 rats than in other age groups, but at doses that altered motor behavior. Conclusions: GNX has anticonvulsant effects against flurothyl-induced seizures in all age groups tested. Its effects are more prominent in the two younger age groups, especially in PN 15 rats, but are associated with motor side effects. [source]

    Extinction in the developing rat: An examination of renewal effects

    DEVELOPMENTAL PSYCHOBIOLOGY, Issue 6 2007
    Carol S.L. Yap
    Abstract In the present series of experiments the context-specificity of extinction was examined from a developmental perspective. For postnatal day (PN) 23 rats, renewal of freezing to an aversive odor conditioned stimulus (CS) was observed when rats were conditioned in Context A, extinguished in Context B, and tested in Context A (i.e., ABA renewal). This effect was not observed in PN16 rats, which is consistent with previous studies suggesting that rats <,PN20 are impaired in encoding contextual information [i.e., Carew and Rudy [1991]. Developmental Psychobiology, 24, 191,209]. Subsequent experiments demonstrated that for rats conditioned at PN16 and tested at PN23, contextual regulation of extinction performance depended on the age at which extinction occurred. Specifically, ABA renewal was observed in rats given extinction training at PN22 but not in rats given extinction training at PN17. These latter results show that whether or not context regulates the expression of an ambiguous memory is determined by the animal's age when the memory becomes ambiguous. © 2007 Wiley Periodicals, Inc. Dev Psychobiol 49: 565-575, 2007. [source]

    Mild carbon monoxide exposure and auditory function in the developing rat

    JOURNAL OF NEUROSCIENCE RESEARCH, Issue 5 2003
    Janet E. Stockard-Sullivan
    Abstract We have examined the influence of chronic mild exposure to carbon monoxide (CO) on cognitive (learning) and auditory function in the developing rat. We have demonstrated that the auditory pathway is compromised at exposures less than 50 ppm, whereas learning was not influenced at 100 ppm. Artificially reared rat pups were exposed to CO during the brain growth spurt and onset of myelination. Spatial learning was assessed using the Morris Water Maze and three tests of auditory function: (1) auditory brainstem conduction times; (2) the amplitude of the eighth nerve's action potential; and (3) otoacoustic emissions carried out on rat pups (age 22, 24 days). The pups were gastrostomy-reared on a rat milk substitute and chronically exposed to CO at discrete concentrations in the range of 12,100 ppm from 6 days of age to post-weaning at 21,23 days of age. We found no difference in auditory brainstem conduction times at all CO concentrations in comparison to non-exposed controls. There was a difference in otoacoustic emissions for test and controls at CO concentrations of 50 ppm but not at lower concentrations. There was a consistent attenuation of the amplitude of the eighth nerve's action potential, even at the lowest CO exposure examined. The attenuation of the amplitude of the action potential of the eighth nerve at 50 ppm carbon monoxide exposure did not completely recover by 73 days of age. We conclude that prolonged mild exposure to carbon monoxide during development causes measurable functional changes at the level of the eighth cranial nerve. © 2003 Wiley-Liss, Inc. [source]

    Contextual modulation of spatial discrimination reversal in developing rats

    DEVELOPMENTAL PSYCHOBIOLOGY, Issue 1 2005
    Jerome H. Pagani
    Abstract Reversal of discrimination learning is influenced by manipulation of the training context. In adult and developing rats, contextual changes made between acquisition and reversal aid the learning of the new discrimination, possibly by serving to release proactive interference from the originally acquired discrimination (M. E. Bouton & D. C. Brooks, 1993; N. Spear, G. Smith, R. Bryan, & W. Gordon, 1980). The present study sought to examine this effect in an appetitive T-maze task, as a function of different contextual manipulations. Rats of three ages, Postnatal Day (PND) 19, PND23, and PND30, were tested for their ability to acquire and reverse a position habit in a T-maze. Contextual changes were made between acquisition and reversal sessions and consisted of one of three manipulations: (a) texture; the texture of the maze floor was changed via the addition or subtraction of wire mesh; (b) maze; subjects were reversed in a different maze that was identical in construction to the training maze, but differed in spatial location; (c) texture and maze; subjects were shifted to the new maze, the floor of which differed in texture from the training maze but was otherwise identical in construction. Results showed that the texture,maze combination was an effective aid to reversal learning at all ages tested. The texture alone, however, was not effective at any age. The maze alone also was an effective cue for reversal, but proved to have the greatest effect for PND30 subjects. During ontogeny, the contextual modulation of reversal learning is importantly influenced by the nature and the salience of the contextual cue. © 2004 Wiley Periodicals, Inc. Dev Psychobiol 46: 36,46, 2005. [source]

    ORIGINAL ARTICLE: Identification of Toll-Like Receptors in the Rat (Rattus norvegicus): Messenger RNA Expression in the Male Reproductive Tract Under Conditions of Androgen Variation

    AMERICAN JOURNAL OF REPRODUCTIVE IMMUNOLOGY, Issue 4 2009
    Barnali Biswas
    Problem, Although the majority of Toll-like receptors (TLRs) are reported in many species, some of them are not yet described in the rat. Further, factors that govern Tlr expression in the male reproductive tract have received little attention. We attempt to identify and characterize Tlrs in the rat and determine the expression profile under conditions that affect male reproductive tract gene expression. Method of study, Rat Tlr5, Tlr10, and Tlr11 transcript sequences were submitted to GenBank and in silico characterization carried out using bioinformatics tools. RT-PCR analyses using gene specific primers for rat Tlr1,13 were carried out with RNA isolated from reproductive tract tissues of various experimental groups. Results,Tlr5, Tlr10, and Tlr11 identified in this study share features that are characteristic of the known TLRs. Abundant Tlr expression was observed in the male reproductive tract of adult and developing rats. Further, Tlr expression was also observed in the epididymides of androgen ablated rats. Conclusion,Tlr5, Tlr10, and Tlr11 are ubiquitously expressed in the rat. Tlrs seem to be expressed during male reproductive tract development and under conditions of androgen ablation, suggesting the preparedness of the male reproductive tract to detect an infection under all conditions of androgen status. [source]

    Is Tryptophan ,more' Essential than Other Essential Aminoacids in Development?

    ANATOMIA, HISTOLOGIA, EMBRYOLOGIA, Issue 5 2009
    A Morphologic Study
    Summary An ontogenetic study was designed on developing rats in uterus of mothers tryptophan deprived at day 1 (exp. 1) and day 14.5 (exp. 2) of conception to verify the supposed determining role of the serotoninergic system (SS) in sexual differentiation in mammals. Tryptophan-free feeding was pursued uninterruptedly in the litter after birth, during lactation and post-natal development. Tryptophan-free pregnant rats were obtained by exclusion of tryptophan sources from chow. In both exp. 1 and exp. 2, the litter showed at birth a significant physical under evolution that worsened, during post-natal development, to a much more marked dwarfism in exp. 1 pups. Growth hormone concentrations in both sexes of dwarf rats were lower than that in the control rats. At 30 days post-natal age, whereas exp. 1 female rats showed a right-timed onset of puberty, no descensus of testes could be observed in male rats of same experiment. Dwarf male rats showed an evident hypotrophy of the whole reproductive apparatus. In histological examination of testes, neither spermatogenesis nor Leydig cells have been observed. Moreover, dwarf female rats showed a pronounced hypotrophy of reproductive organs, but a normal puberal status pattern was evident. In exp. 2, litters showed a less pronounced dwarfism, but a normal right-timed onset of puberty in both male and female rats. Data indicate that role of tryptophan in physical and sexual maturation in both male and female rats is essential. [source]

    Oligodendrogenesis: The role of iron

    BIOFACTORS, Issue 2 2010
    Maria Elvira Badaracco
    Abstract Iron seems to be an essential factor in myelination and oligodendrocyte (OLGc) biology. However, the specific role of iron in these processes remains to be elucidated. Iron deficiency (ID) imposed to developing rats has been a relevant model to understand the role of iron in oligodendrogenesis and myelination. During early development ID causes specific changes in myelin composition, including a lower relative content of cholesterol, proteolipid protein (PLP), and myelin basic protein 21 (MBP21). These changes could be a consequence of the adverse effects of ID on OLGc development and function. We subsenquently studied the possible corrective effect of a single intracranial injection (ICI) of apotransferrin (aTf) on myelin formation in ID rats OLGc migration and differentiation after an ICI of aTf was evaluated at 3 days of age. ID increased the number of proliferating and undifferentiated cells in the corpus callosum (CC), while a single aTf injection reverts these effects, increasing the number of mature cells and myelin formation. Overall, results of a series of studies supports the concept that iron may affect OLGc development at early stages of embryogenesis rather than during late development. Myelin composition is altered by a limited iron supply, changes that can be reverted by a single injection of aTf. [source]