Cerebellar DNA Research Articles

Dihydroergotoxine and ethanol: physiological and neurochemical variables in male mice.

The residual effects of dihydroergotoxine mesylate (DHET: active substance of Hydergine), ethanol, and DHET + ethanol were investigated in aging male mice. Prolonged alcohol or DHET consumption was found to prolong hexobarbital sleeping time and increase oxygen consumption. Administration of alcohol combined with DHET inhibited the ability of each drug to prolong hexobarbital sleeping time and increase oxygen consumption. There were no significant differences between groups in forebrain synaptosomal (Na+-K+) adenosine- triphosphatase and acetylcholinesterase activity or cerebellar protein, DNA and RNA content. The relative proportion of phospholipid to protein in isolated myelin of the medulla was significantly reduced, whereas the sphingomyelin content of total phospholipid was highest in alcohol-treated mice. Conocomitant treatment of mice with alcohol combined with DHET prevented the physiological and neurochemical changes caused by alcohol and, in some cases, DHET, administered alone.

Effects of methylazoxymethanol given at different stages of postnatal life on development of the rat brain. Comparison with those of thyroid deficiency.

Newborn rats were treated at different stages of their development with low doses of methylazoxymethanol acetate. The postnatal increase of the DNA content of the cerebrum did not differ from that of controls. In the cerebellum, the DNA content was transitorily reduced, but later, the external granular layer became thicker and DNA deposition increased in comparison with controls; finally, the cerebellar DNA returned to a normal value. Morphological abnormalities of the cerebellum, abnormal orientation of migrating cells, scattering of Purkinje cell bodies within the internal granule cells and specially striking abnormalities of the morphology and orientation of Purkinje cell dendrites were noted in rats treated with MAM from birth to day 3. The effects of the Purkinje cell morphogenesis persisted but were much less marked when MAM was given from 4 to 7 or from 8 to 11 days. Neonatal thyroid deficiency, as MAM-treatment between days 0 and 3, leads to an abnormal position of Purkinje cell bodies within the cerebellar cortex; it also leads to morphological abnormalities of their dendritic arborization which closely resemble those observed after MAM-treatment during the second postnatal week. It also alters the cell formation in the cerebellum. Thyroid deficiency probably exerts its effect on cell formation earlier than previous biochemical studied have shown. On another hand, the morphological abnormalities of Purkinje cell arborizations in the thyroid-deficient animals may be partly due to the perturbations of cell formation which persist later in the cerebellum.

Pyrimidine metabolism during restorative brain growth after neonatal undernutrition in the rat.

Three litters of 20 Wistar rat pups each were maintained until age 6 days at which time only the 4 lightest and 4 heaviest pups from each litter were left with the mother until age 13 days. Three control litters of eight pups each were also maintained for 13 days. At that time, the undernourished light pups showed body weight, cerebellar weight, and cerebellar DNA, respectively, of 79.2%, 86.6%, and 90.4% compared with a "combined control" group consisting of control pups plus undernourished heavy pups which were statistically indistinguishable with regard to these three measurements. After the week of "catch-up" or restorative body and brain growth, activities of enzymes from metabolic pathways leading to pyrimidine and nucleic acid biosynthesis were measured in cerebella from all three groups (control, undernourished heavy, and undernourished light). The salvage pathway enzyme thymidine kinase (TK) and the inter-conversion pathway enzyme thymidylate synthetase (TS) in the undernourished light group showed significant elevations of 32% and 11%, respectively, above activity in the combined control group. The salvage pathway enzyme uridine kinase (UK) and the de novo pathway enzyme aspartate transcarbamylase were not significantly different in cerebella from these two groups. The significant elevation in TK and TS in undernourished pups suggest that these enzymes are critical for restorative brain growth. The significant elevation of TS indicates that the inter-conversion pathway converting available uridylate, a ribonucleotide, to thymidylate, a deoxyribonucleotide, is activated in order to augment DNA biosynthesis.

RELATION OF THYMIDYLATE SYNTHETASE (TS) ACTIVITY TO DNA ACCUMULATION RATE IN DEVELOPING RAT CEREBELLUM: EFFECT OF HYPER- AND HYPOTHYROIDISM

TS, an enzyme of the pathway by which uridylate (an RNA precursor) is converted to thymidylate (a DNA precursor), is elevated in cells undergoing replicative DNA synthesis.We measured TS activity and DNA content in developing cerebellum of normal, thyroxine-treated, and propylthiouracil-treated neonatal rats. An expression for cerebellar DNA accumulation rate (DAR) was derived by differentiation of the equation obtained using the method of least squares to fit a slgmoid curve (y=A/l+be−cc) to cerebellar DNA content versus age.Hyperthyroidism induced by thyroxine significantly increased both TS activity and DAR above control values on days 2-7, and significantly decreased both measurements below control on days 9-15. The coefficient of correlation between TS activity and DAR was 0.96 for control and hyperthyrold pups.Hypothyroidism induced by administration of propylthiouracil (PTU) to nursing dams significantly decreased both TS activity and DAR below control values by age 5 days and significantly increased both measurements above control on days 15-21. The coefficient of correlation between TS activity and DAR was 0.98 for pups of both control and PTU-treated dams.The close correlation between cerebellar TS and DAR in control, hyperthyroid, and hypothyroid animals supports the possibility that TS may be critical in the control of cell replication rate in developing rat cerebellum.

EXPERIMENTAL HYPOTHYROIDISM: RELATIONSHIP BETWEEN CEREBELLAR CELL DIVISION AND ENZYMES INVOLVING NUCLEIC ACID METABOLISM DURING DEVELOPMENT

Perinatal hypothyroidism in the rat results in a delay in the developmental spectrum of cerebellar cell replication with a shift to a later age in the developmental spectrum of activity of thymidine kinase (TK), a salvage pathway enzyme active in replicative DNA synthesis. In the present experiments hypothyroidism was induced by administration of propylthiouracil (PTU) to the mother from the 18th day of gestation. We measured cerebellar activities of uridine kinase (UK), aspartate transcarbamylase (ATC), and thymidylate synthetase (TS). These enzymes are associated with the salvage of uridine, de novo synthesis of uridylate, and conversion of uridylate to thymidylate respectively, and their peak activities normally occur near the time of most rapid cerebellar DNA synthesis. Activities of ATC at age 3 days and TS at age 5 days were significantly decreased to 91.3% and 94% of control respectively, while activities were significantly elevated to 116% and 142% of control by day 15. UK activity was unaffected by hypothyroidism after 5 days of age. The shift to a later age in the developmental spectrum of ATC and TS supports the possibility that the de novo and interconversion pathways relate closely to replicative DNA synthesis, whereas the salvage pathway for uridine may relate more closely in brain to the synthesis of RNA and the sustaining of non-dividing cells.

Thyroxine Effect upon Activity of Uridine Kinase in Developing Rat Cerebellum

Experimental hyperthyroidism in the neonatal rat is known to accelerate cerebellar DNA biosynthesis resulting ultimately in a deficit in cell number at maturity. Because of the know shift to an earlier age in the developmental curve for cerebellar thymidine kinase activity in rats treated with thyroxine, we studied the activity of uridine kinase and DNA biosynthesis during rat cerebellar development under hyperthyroid conditions. Body weight and cerebellar wet weight in treated animals were noted to be significantly decreased below control values on days 4 and 12, respectively. Cerebellar DNA was significantly elevated above control values on days 4 and 6 (132 and 129% of control, respectively). Subsequently, DNA content fell significantly below control values through day 18. Uridine kinase activity was found to be increased significantly above control values at ages 2, 4, and 6 days (maximum 119% of control at age 4 days) following which activity fell significantly below control values by 15 days of age. Uridine kinase activity from both treated and control animals fell only moderately after the time of peak activity between 9 and 15 days of age, although the peak of the developmental curve for the enzyme appeared earlier in the treated animals. The data show a less pronounced early stimulation of cerebellar uridine kinase by thyroxine compared with previously reported thyroxine enhancement of thymidine kinase activity, although both enzymes are affected by thyroxine throughout cerebellar ontogenesis. The study thus provides evidence that uridine kinase is sensitive to hormonal stimulation during early stages of active cerebellar cell division, and that the enzyme may relate most closely in brain to the synthesis of RNA as well as the sustaining of cell function after the most active phase of cellular proliferation. In addition, the study emphasizes the use of enzyme-hormone relationships during development to provide information concerning critical interrelationships between metabolic pathways contributing to nucleic acid biosynthesis.

Effect of Hypothyroidism on Aspartate Transcarbamylase, Uridine Kinase, and DNA Biosynthesis during Cerebellar Development in the Rat

Experimental hypothyroidism in the neonatal rat is known to retard cerebellar DNA biosynthesis with a return to normal of the ultimate cell number. Because of the known shift to a later age in the developmental curve for cerebellar thymidine kinase in hypothyroid rats, we studied the activities of aspartate transcarbamylase (ATC) and uridine kinase (UK) during cerebellar development in rats rendered hypothyroid by daily intragastric administration of propylthiouracil to the mother after 18 days gestation. Body weight and cerebellar wet weight in treated animals were noted to be significantly decreased below control values by day 5. Cerebellar DNA was significantly decreased below control values by day 5 with a maximum deficit of 64.9% of control on day 9, and a decrease in deficit to 80.9% of control on day 21. ATC activity in cerebella of hypothyroid rat pups was significantly below that of controls at age 5 days, and by age 15 and 21 days was significantly elevated above control values (91.4, 116, and 154% of controls respectively), thus suggesting a shift to a later age for activity of this enzyme in the hypothyroid state. UK activity in cerebella of hypothyroid pups was significantly below that of activity in control cerebella at age 5 days, but was not significantly different from controls at any of the later ages. Activity of UK in both treated and control cerebella remained relatively elevated by age 21 days with respect to the maximum activity in controls at age 9 days. The shift to a later age in the developmental spectrum of cerebellar ATC activity, an enzyme representative of the <i>de novo</i> pathway for pyrimidine biosynthesis, suggests that the enzyme is involved in the mechanism whereby cerebellar cell division is suppressed and subsequently prolonged in the hypothyroid state. The lack of an influence of hypothyroidism on cerebellar UK activity after day 5 of development supports previous observations that this enzyme may relate in brain to the synthesis of RNA and to cell functions not specifically related to proliferation. The study reveals the differential effects of neonatal hypothyroidism on enzymes representing two of the pathways involved in pyrimidine and nucleic acid biosynthesis during the thyroid hormone-sensitive period of early mammalian brain development, and emphasizes the necessity for further biochemical studies involving tissue pool sizes of <i>in vivo</i> intermediates and serum concentrations of nucleic acid precursors in order to further delineate the relative contribution of each pathway essential for nucleic acid metabolism during development.

The effect of 5-bromodeoxyuridine on the postnatal development of the rat cerebellum: A biochemical study

The effect of a thymidine analog, 5-bromodeoxyuridine (BrdU), on the post-natal development of the cerebellum was studied. Rats were injected with 15 mg per 100 gram body weight of BrdU twice a day for 3 consecutive days from the second day after birth, and were killed at 5, 7, 15, 22 and 35 days of age. One hour prior to killing, the rats were given tritiated thymidine. The cerebellar DNA, RNA, protein and cerebroside, and the incorporation of thymidine were measured. BrdU administration caused a markedly retarded growth of the body and the cerebellum. At 35 days of age, the weights of the body and the cerebellum were 42 and 69% of the controls. Quantitative measurements of cerebellar nucleic acids and isotope uptake correlated well with previous morphological observation, and indicated that the analog caused a transient inhibition of cell formation and possibly destruction of stem cell population of the external granular layer. This inhibitory effect was compensated later by a more rapid DNA deposition and a prolongation of the period of cell proliferation. However, the restitution was incomplete and resulted in a permanent deficit in the final cell number, as reflected by the reduction in the size of the cerebellum of the BrdU-treated rats.

In vivo reversal of thyroxine induction of DNA synthesis by dibutyryl cyclic AMP in developing rat cerebellum

Thyroxine, dibutyryl cyclic AMP, and a combination of both drugs were administered daily from birth to 2, 2 and 3 pups, respectively from each of 5 litters of Sprague-Dawley rats. Body weight, brain weight, cerebellar weight, and cerebellar DNA were measured in each animal at age 5 days and compared with values from a pair of controls from each litter. Cerebellar weight and DNA content were affected more severely than body weight in cyclic AMP-treated animals, with cerebellar DNA reduced significantly to 88% of control values. Cerebellar DNA was significantly elevated to 117% of control values in thyroxine-treated animals. This augmentation of cerebellar DNA synthesis by thyroxine was negated by administration of dibutyryl cyclic AMP 10 min prior to the thyroxine injection. These results support an hypothesis that the enhancement of cerebellar cell division by thyroxine involves an increase in the ratio of intracellular cyclic guanosine monophosphate to cyclic adenosine monophosphate. The reversal of the thyroxine-induced increase in cerebellar DNA synthesis by a prior injection of dibutyryl cyclic AMP suggests that the early stimulation of cell division by thyroxine may be mediated by cyclic AMP, and that the intracellular balance between cerebellar cyclic AMP and cyclic GMP was distorted by in vivo elevation of intracellular cyclic AMP levels.

EFFECTS OF HYPOTHYROIDISM AND UNDERNUTRITION ON DNA CONTENT AND THYMIDINE KINASE ACTIVITY DURING CEREBELLAR DEVELOPMENT IN THE RAT1,2

Abstract—The effects of hypothyroidism and several degrees of undernutrition on the development of cerebellar weight, DNA, and thymidine kinase activity were studied in young rats ranging in age from 2 to 22 days. Early propylthiouracil treatment caused a delayed cerebellar cell multiplication. The activity of cerebellar thymidine kinase was suppressed at ages 2 and 5 days and was in excess of control values on days 15 and 22, thus resulting in a delay in the developmental spectrum for thymidine kinase, and extending the time span of activity beyond that of controls. Undernutrition led to varying degrees of reduced cell proliferation at experimental ages 5, 12, and 19 days. Cerebella from the most undernourished animals showed significant differences from controls in thymidine kinase activity at ages 5 and 12 days. Comparisons between sub‐groups from within the oversized litters at 5 and 12 days suggested that changes in thymidine kinase activity relate to the degree of undernutrition to which the sub‐group is subjected and that during development there may be a critical degree of undernutrition at which a particular essential enzyme becomes affected.This study emphasizes the biochemical similarities and differences between neonatal hypothyroidism and undernutrition, while pointing out the difficulties which exist in biochemical separation of components of the two conditions. Further evidence is presented that thymidine kinase is responsive to hormonal stimuli during cerebellar development and may play an important role in the regulation of DNA biosynthesis in brain as well as other organs.

Effect of thyroid deficiency on cell acquisition in the postnatal rat brain: A quantitative histological study

The mechanisms underlying transient reduction of cell number in the developing cerebellum of thyroid-deficient rats have been studied by quantitative histtological methods. Thyroid deficiency has no significant effect on the generation cyccle of dividing cells in either the subependymal layer of the lateral ventricular walls or the external granular layer of the cerebellum: the length of the cell cycle and the duration of the different phases of the cycle, including the DNA synthesis time appears to be normal. However, the external granular layer of the cerebellum contains fewer cells than in control at 12 days. Pyknotic nuclei are prominent in the granule cell layer of the hypothyroid cerebellum at this age. These amount to an estimated loss of about 1% of the total cerebellar cell population in 24 h. It is suggested that death of granule cells is for the most part a consequence of reduced Purkinje cell dendritic arborization, with failure of parallel fibre/Purkinje cell synaptogeneiis. In the second postnatal week, granule cell death and reduced numbers of cells in the germinal zone can account to a great extent for the observed shortfall in cerebellar DNA content. The eventual attainment of normal cell numbers in the cerebellum of hypothyroid rats is related to a persistent external granular layer in the fourth and fifth postnatal weeks.

Comparative studies of DNA size in various tissues of mice during the aging process

The sizes of single-strand pieces of DNA were estimated by alkaline sucrose gradient centrifugation in four tissues of C57BL/6 mice at 1–-2 months, 14 months and 22 months of age. When the DNA sizes in 14 and 22 months old mice were compared with those of the 1–2 months old group, the splenic, thymic and cerebellar DNA of old mice were not significantly different from those of the young mice. However, hepatic DNA of 14 months old mice was significantly smaller than that of 2 months old. That of 22 months old was similar to that of 14 months old mice. The increase of DNA scissions from 2 to 14 months old was 3·2×10 4 breaks per cell. If we assume a constant and continuous rate of DNA scission, the rate would be about 88 breaks per cell per day or about 4 breaks per cell per hour. X-iradiation of 500 R administered at 2 months old did not cause any significant difference in DNA size from a non-irradiated group when examined at 14 and 22 months old.

Thyroid Hormone and Cell Formation in the Developing Rat Cerebellum

Effects of neonatal hyperthyroidism on cell formation in the developing rat cerebellum were reinvestigated. Administration at birth of excessive doses of thyroxine or triiodothyronine led to an early stimulation of cell acquisition, followed by a permanent deficit of cells in the cerebellum. The corrective effects of physiological doses of thyroxine on the troubles of the histological and biochemical development of the cerebellum in thyroid-deficient animals were also studied. As early as 6 days, cell maturation and formation were already retarded in animals treated with propylthiouracil, but, as previously reported, cell formation was prolonged and the final number of cells was normal. Administration to thyroid-deficient animals of progressively increasing doses of thyroxine, nearly equal to the amounts of hormone secreted by the thyroid gland of the developing normal rat, returned the evolution of the cerebellar wet weight and of the cerebellar DNA to normal, as well as the histological maturation of the cerebellum, even if it did not entirely correct the retardation of body growth. These results are consistent with the view that thyroid hormone early stimulates maturation of the cerebellar germinative cells and subsequently interacts with cell formation in the cerebellum, and that this action is physiological.

Effect of thyroxine on DNA synthesis and thymidine kinase activity during cerebellar development

Body growth, cerebellar growth, cerebellar DNA content, and cerebellar thymidine kinase activity were studied in rats made hyperthyroid from birth, and littermate controls. Hyperthyroidism caused the following. (1) Significantly decreased body weight in treated animals aged 3 days and older. (2) A significant decrease in cerebellar wet weight at age 12 days and later in treated animals. (3) A significant increase in cerebellar DNA by the age of 2 days in treate animals, continuing through the age of 6 days. By the age of 12 days, cerebellar DNA content was significantly decreased below control values in treated animals. (4) An induction of cerebellar thymidine kinase activity in treated animals by age 1 day continuing through age 5 days, with maximum elevation being 137% of control values at age 4 days. By age 9 days, cerebellar thymidine kinase activity in treated animals had fallen to levels significantly below control values and activity was minimal at age 15 days in comparison to disappearance of activity around age 18 days in cerebella of control animals. (5) DNA synthesis is thus accelerated in cerebella of thyroxine treated animals aged 2 to 6 days and subsequently total cerebellar DNA fails to reach normal values. Thymidine kinase activity in cerebella of treated animals is induced by age 1 day, prior to the increase of cerebellar DNA content in treated animals, and subsequently falls below control values by age 9 days, prior to a significant decrease in DNA below control values. This apparent shift to the left in the developmental spectrum of cerebellar thymidine kinase activity compared to the effects of thyroxine on DNA synthesis is discussed in the light of what is known about the effects of hormones on enzyme systems and possible mechanisms of action of thyroid hormones. The conclusions are drawn that thyroxine appears to induce thymidine kinase activity in early cerebellar development and appears to be related to premature decrease of enzyme activity. In addition, our findings support the possibility that thymidine kinase may be an essential regulatory enzyme in DNA biosynthesis, and that the effects on thymidine kinase and DNA biosynthesis of thyroxine in developing cerebellum may be secondary to a modulation of gene activity by the hormone.

Glucocorticoid effect upon thymidine kinase in the developing cerebellum.

Extract: Forty-nine litters of eight Sprague-Dawley rat pups were divided into four pups treated with 0.6 mg hydrocortisone acetate on the day of birth and four littermate controls. The mean body weight, cerebellar weight, and cerebellar DNA were significantly depressed in treated pups by 3 days of age, with all three of these measurements of growth increasing in rate around 9 days of age, but remaining well below control values throughout 15 days of age. Body weight and cerebellar DNA were maximally depressed at age 12 days (37.7% and 46.6% of control values, respectively), and cerebellar wet weight was maximally depressed to 51.5% of the control value at 9 days of age. The activity of thymidine kinase, a salvage pathway enzyme for pyrimidine biosynthesis, was found to be depressed to 80.2% and 74.1% of the control value at 3 and 6 days of age, respectively and elevated to 134% and 158% over control values at ages 12 and 15 days. The depression of thymidine kinase activity by hydrocortisone at ages 3 and 6 days followed by the overshoot of enzyme activity after steroid-induced growth suppression had subsided suggests that the thymidine kinase may be considered as having an essential regulatory function in the rate of DNA synthesis in developing brain.Speculation: Extrapolation of these hormone-enzyme relations in developing rat cerebellum to the clinical use of glucocorticoids in acceleration of lung maturation in human premature infants suggests the possibility that concomitant effects of the steroid may be detrimental to the development of brain areas which undergo cell replication at the time the drug is administered.

DNA SYNTHESIS AND THYMIDINE KINASE ACTIVITY DURING CEREBELLAR DEVELOPMENT: EFFECT OF THYROXINE

Thyroid hormone administered from birth has been found to increase cerebellar DNA production in the rat by 6 days of age and to decrease DNA synthesis thereafter. This acceleration of development under hormonal influence has led to studies involving the relationship between thyroxine, DNA and activities of enzymes involving pyrimidine biosynthesis during cerebellar development. Using daily doses of thyroxine, we found rat cerebellar DNA to be increased significantly above control values by age 2 days until age 6 days. Following that, cerebellar DNA synthesis decreased to 78% of control values by age 12 days. The activity of thymidine kinase, a salvage pathway enzyme for pyrimidine biosynthesis, was found to be significantly elevated over control values by age 1 day. This elevation of enzyme activity in cerebella of treated animals continued until age 5 days, at a maximum of 137% of control values, following which activity fell significantly below control values by 9 days of age. Thyroxine thus appears to induce thymidine kinase activity in early cerebellar development and is apparently related to premature decrease of activity. These findings provide evidence that thymidine kinase may be subject to hormonal control, and may be a critical regulatory enzyme for cerebellar DNA biosynthesis.

GLUCOCORTICOID EFFECT UPON THYMIDINE KINASE IN DEVELOPING CEREBELLUM

Glucocorticoids have been used in animal models and more recently in human studies as a means to accelerate neonatal lung maturation in order to prevent the respiratory distress syndrome in premature infants. Little attention has been paid to the possible effects of glucocorticoids upon developing organs other than lung. Recent studies of cortisol administration on DNA content in developing rat brain showed an early reduction as well as a permanent defecit in cerebellar DNA. In addition to confirming these findings, we have shown cortisol administration in the early neonatal period to have a profound effect on thymidine kinase, a salvage pathway enzyme for pyrimidine biosynthesis, in rat cerebellum during early development. Thymidine kinase normally peaks in activity in rat cerebellum at approximately 6 days of postnatal age and falls rapidly thereafter. With cortisol administration, enzyme activity is maximally suppressed at 6 days of age using both normal and undernourished controls. These findings suggest that neonatally administered glucocorticoids may have effects which are potentially detrimental to areas of the central nervous system which may be undergoing cell replication during the time the drug is administered. Thus the possible use of glucocorticoids for their salutary effects in the respiratory distress syndrome may necessitate consideration of any hazardous effects, however subtle, upon central nervous system development.

Neonatal malnutrition: neurochemical, hormonal and behavioral manifestations

An effective state of malnutrition was imposed on rat pups throughout their postnatal period of development by feeding the lactating dams a 12% casein diet. Controls were fed a 24% casein diet. The malnourished pups exhibited such signs of retarded physical development as reduced body growth and delayed eye opening. At weaning brain weights were reduced and regional brain analysis revealed distortions of chemical composition. These changes included a general reduction of cholesterol concentration, decreased cerebellar DNA content (indicative of cell number), and reduced telencephalic and brain stem protein: DNA ratios (reflecting cell size). The cerebellum also displayed reduced AChE activity suggesting an appreciable effect on its synaptic elements, particularly involving the cholinergic system. Brain stem concentrations of 5-HT and 5-HIAA were increased, implying activation of the central serotonergic neurohumoral system. Possibly related to this, a concomitant increase of adrenal corticosterone was revealed, implicating the additional involvement of the pituitary-adrenal axis in the consequences of postnatal malnutrition. Behaviorally, the previously malnourished weanlings displayed a state of heightened ‘emotionality’. Their performance in a 2-way shuttle task was also markedly abnormal. It is proposed that the enhanced activation of the brain stem serotonergic system may, at least partially, underlie the state of heightened ‘emotionality’, which is the most characteristic behavioral manifestation of perinatal malnutrition.

Brain cell number and motor activity in rats subjected to neonatal undernutrition

Rat pups were undernourished until weaning by raising them in oversized litters. After weaning they were fed ad lib . Control subjects were raised in normal-sized litters and fed ad lib . After weaning. They were all examined between 4 and 5 weeks of age in 3 behavioral tests, measuring various aspects of motor capabilities: orienting locomotor activity, rotarod performance, and activity wheel running. Following the completion of behavioral studies the animals were sacrificed and cerebral and cerebellar DNA (cell number) were assayed. Comparisons between control and undernourished groups revealed significant reduction in body weights in the undernourished subjects, both at weaning and at the time of behavioral testing. Cerebral and cerebellar DNA were reduced in the undernourished rats as compared to controls. No difference was noted between the groups in rotarod performance or activity wheel running. The orienting locomotor activity, however, was greater in controls than in undernourished subjects. When these one-hour activity counts were divided into periods, the early counts did not differ between groups, while the counts late in the hour were significantly less in the undernourished animals. Thus, while the high counts of the initial orienting response were unaffected by the state of nutrition, the decay with habituation occurred at a more rapid rate in the rats that were poorly nourished. Cerebellar levels of DNA were found to correlate with locomotor activity counts, but cerebral DNA levels did not. The findings suggest that cerebellar underdevelopment can influence behavior in subtle ways not clearly associated with deficiencies in control of skeletal muscle tone or coordination.

Brain biochemical changes in rats treated with chlorpromazine and electroshocked during early postnatal development

The activities of cerebral and cerebellar acetylcholinesterase (AChE), butyrylcholinesterase (BuChE), DNA, RNA and protein contents were studied in female rats treated with chlorpromazine (6 mg/kg body weight or 15 mg/kg) either at 2 (CPZ-2 day) or 13 days (CPZ-13 day) after birth and electroshocked beginning at 12 days for the CPZ-2 day groups or 18 days for the CPZ-13 day groups. Both cerebrocortical and cerebellar BuChE were higher in all control shocked groups whereas only cerebellar DNA was higher as compared to non-shocked controls. Chlorpromazine treatment lowered only the cerebral BuChE activity but this effect was not apparent after electroshock. Although chlorpromazine alone did not affect DNA content in either the cerebral cortex or cerebellum, it prevented the rise of DNA induced by electroshock in the cerebellum.