Minimal behavioral effects from developmental cerebellar stunting in young rats induced by postnatal treatment with alpha-difluoromethylornithine

A study of D-allulose-associated reproductive toxicity in rats

In this study, we assessed whether D-allulose was associated with reproductive toxicity in rats, assessing reproduction and offspring growth following gavage of parents with 0, 500, 1000, and 2000 mg/kg of this compound. Specifically, female rats were continuously dose from 2 weeks prior to mating until day 21 of lactation, while males were dose for the 10 weeks before mating. We did not observe any direct toxicity or mortality upon D-allulose administration, with no changes in body weight or eating behavior between study and control groups. We also did not observe any significant alterations in precoital time, copulation index, fertility index (male), or pregnancy index (male) between groups. Relative to controls, there was also no effect of D-allulose treatment on pregnancy rates, implantation, pregnancy length, gender ratios, viability indexes, lactation indexes, prenatal death rates, or number of live young at time of birth. Organ weights and indexes were also comparable between groups at time of sacrifice, and treatment was not linked to any obvious manifestations upon necropsy or histopathological examination. In the F1 offspring, the body weights of pups born to parents administered D-allulose (2000, 1000, and 500 mg/kg) were slightly higher on days 1-9 postnatally relative to controls (p < 0.05), however after day 9 these effects were no longer evident. Together, these results indicate a no-observed-adverse-effect level (NOAEL) of D-allulose of 2000 mg/kg, the highest dose tested, in parental animals and their offspring.

Repeated malathion exposure induces behavioral impairment and AChE activity inhibition in brains of rat pups

The present study evaluated if repeated malathion administration would cause behavioral impairment in rat pups. Na+K+ ATPase and acetylcholinesterase (AChE) activities were investigated in brains of rat pups. Malathion was administered (100 or 200 mg/kg) orally (p.o.), once a day for four consecutive days. Rat pups were submitted to behavioral tests on the 5th day, 24 h after the last malathion administration. Malathion at the dose of 200 mg/kg caused a significant increase in the negative geotaxis latency and a decrease in the rotarod latency of rat pups. Rat pups exposed to malathion at both doses showed a significant decrease in the forelimb support latency and an inhibition of brain AChE activity. Repeated exposure of rat pups to malathion caused a decrease in motor coordination, vestibular function and muscular strength/coordination. The brain activity of AChE is involved in the behavioral alterations caused by malathion in rat pups.

Preweaning behaviors, developmental landmarks, and acrylamide and glycidamide levels after pre- and postnatal acrylamide treatment in rats

At high levels of exposure, acrylamide monomer (AA) is a known neurotoxicant (LoPachin, 2004 [23]). The effects of lower levels of exposure, such as those experienced via a typical human diet, have not been widely investigated. Data at these levels are particularly relevant given the widespread human exposure through carbohydrate-containing foods cooked at high temperatures. Additionally, daily AA intake is estimated to be higher for infants and children. Earlier, we described behavioral alterations in preweaning rats resulting from developmental AA treatment (0.5-10.0mg/kg/day) (Garey et al., 2005 [14]). In the present study, the effects of lower doses were measured as well as serum AA and glycidimide (GA) levels in dams, fetuses, and young pups. Pregnant Fischer 344 dams (n=48-58/treatment group) were gavaged with 0.0, 0.1, 0.3, 1.0, or 5.0mg AA/kg/day beginning on gestational day 6 and ending on the day of parturition. Beginning on postnatal day 1 (PND 1) and continuing through PND 21, all pups/litter were gavaged with the same dose as their dam. There were no AA treatment effects on offspring fur development, pinnae detachment, or eye opening. Offspring body weight was somewhat decreased by 5.0mg/kg/day, particularly in males. However, righting reflex (PNDs 4-7), slant board (i.e., negative geotaxis) (PNDs 8-10), forelimb hang (PNDs 12-16), and rotarod behavior (PNDs 21-22) were not significantly altered by AA treatment. Male and female offspring of the 5.0mg/kg/day group were 30-49% less active in the open field at PNDs 19-20 (p<0.05). Serum AA levels of GD20 dams and their fetuses were comparable, indicating the ability of AA to cross the placental barrier. AA levels of pups were not affected by age (PND 1 and 22) or sex. In all rats, serum AA and GA levels exhibited a dose-response relationship. These data extend those of our previous study (Garey et al., 2005 [14]) and demonstrate that overt preweaning neurobehavioral effects are apparent in rats exposed to acrylamide pre- and postnatally, but only at the highest doses tested.

Neonatal PCP is more potent than ketamine at modifying preweaning behaviors of Sprague-Dawley rats

Treatment with N-methyl-D-aspartate (NMDA) receptor antagonists, such as ketamine (KET) or phencyclidine (PCP), can trigger apoptotic neurodegeneration in neonatal rodents; however, little is known about the behavioral alterations resulting from such treatment. Here, rats were sc treated with saline; 10 mg/kg PCP on postnatal days (PNDs) 7, 9, and 11; 20 mg/kg KET (six injections every 2 h on PND 7); or a regimen of ketamine and 250 mg/kg L-carnitine (KLC) both administered on PND 7 with additional 250 mg/kg doses of L-carnitine given on PNDs 8-11. Postinjection, the home cage behavior of each pup was categorized on PNDs 7-11. Slant board and forelimb hang behaviors were examined on PNDs 8-11 and 12-16, respectively. The initial KET or KLC injections on PND 7 elevated abnormal home cage activity (i.e., paresis and paddling); however, KLC pup behavior returned to normal by the fourth injection, indicating the protective effects of L-carnitine against NMDA antagonist toxicity. PCP treatment caused substantial abnormal home cage activity on each injection day (PNDs 7, 9, and 11). Latencies to turn on the slant board were significantly longer on PND 8 for KET- and PCP-treated pups and PND 10 for PCP-treated pups. On PND 12, the forelimb hang time of PCP-treated pups was significantly shorter. Body weight was decreased on PNDs 8-18 in PCP-treated pups and PNDs 8-10 in KET-treated pups. These data indicate that developmental NMDA antagonist treatment causes short-term behavioral alterations which appear related to motor coordination and may be cerebellar in nature. Furthermore, single PCP injections appear more potent at altering behavior than multiple injections of KET.

Animal models concerning the role of dopamine in attention-deficit hyperactivity disorder

Several models of attention-deficit hyperactivity disorder (ADHD) have been proposed, ranging from administration of neurotoxins to genetically manipulated models. These models are used to gain insight into ADHD as a disorder and assist in the discovery of new therapeutic strategies. However, the information gained from these models differs, depending to a large extent on the validity (or otherwise) of the model. Thus the insights gained from these models with respect to the pathophysiology and aetiology of ADHD remains inconclusive. No animal model resembles the clinical situation of ADHD perfectly but good animal models of ADHD should mimic its characteristics, confirm to an underlying theory of ADHD and ultimately make predictions of future therapies. While the involvement of dopamine (DA) in ADHD has been established, the evaluation of rodent models of ADHD particularly with respect to dopaminergic systems is attempted here. It is concluded that the neonatal 6-hydroxy-dopamine lesioned rat and DA transporter knockout/knockdown mice have the highest degree of validity for ADHD.

Behavioral effects of prenatal folate deficiency in mice

BACKGROUND

Folate supplementation decreases the incidence of birth defects such as neural tube defects (NTDs). We and others have shown that gestational dietary folate deficiency that does not produce overt NTDs can alter fetal neural histology. Accordingly, murine offspring were examined for the possible functional consequences of prenatal folate deficiency.

METHODS

CD-1 mice were fed a diet of chow containing 400, 600, or 1200 nmol of folic acid/kg of chow for eight weeks prior to breeding and until GD18, at which time all dams were placed on folate-replete chow. Behavioral tests of male and female offspring included righting reflex, negative geotaxis, forelimb hanging, motor coordination, open field activity, and elevated plus maze activity.

RESULTS

Of greatest significance, the adult offspring that were prenatally folate-deficient exhibited more anxiety-related behavior in the elevated plus maze. Offspring of the 400 nmol of folic acid/kg of chow diet group exhibited significantly shorter durations in the open arms and longer durations in the closed arms. Further, these two behaviors were dose-related. There was also a trend for the prenatally folate-deficient adult mice to exhibit more thigmotaxis (wall-hugging) behavior in the open field, entering the central area less frequently than controls. There were few other differences in tested behaviors between folate-deficient and folate-replete mice.

CONCLUSIONS

Prenatal folate deficiency that is repleted at birth can manifest later with increased anxiety 9-12 weeks after birth.

Developmental and behavioral effects of acrylamide in Fischer 344 rats

Human exposures to acrylamide (ACR), a known neurotoxicant, can occur via a variety of substances, including cigarette smoke and the ingestion of certain carbohydrate-based foods cooked at high temperatures. In this study, Fischer 344 sperm plug-positive female rats were treated daily with ACR (0, 0.5, 1.0, 2.5, 5.0 or 10.0 mg/kg/day) by gavage beginning on gestation day 7. Dosing of dams ended when litters were born; pups received daily gavage at the same dose as their dam from postnatal day (PND) 1 through PND22. Pups were tested using a battery of behavioral assessments from PNDs 4-22. Statistically significant decreases in body weight were observed in pups exposed to ACR at doses as low as 1.0 mg/kg/day (treatmentxday; repeated measures ANOVA, P<0.0001). No statistically significant differences among treatment groups were observed in righting reflex, forelimb hang, or open field measures of activity. Statistically significant effects of ACR were observed at the 10 mg/kg/day dose on negative geotaxis performance (P<0.01) and a linear trend in fall-time latencies on Rotarod performance on PNDs 21-22 (P<0.05), with higher doses producing shorter latencies. These results suggest that ACR exposure produces deficits in development and motor coordination that are observable before weaning.

Neonatal dexamethasone on day 7 in rats causes behavioral alterations reflective of hippocampal, but not cerebellar, deficits

Developmental glucocorticoid treatment in rats has been shown to cause body and brain weight decrements concurrent with behavioral alterations. Here, Sprague-Dawley rats were treated with the synthetic glucocorticoid, dexamethasone (DEX), on postnatal day (PND) 7 (1.5 mg/kg, sc, injected in the morning and afternoon). Behavioral assessments of negative geotaxis, locomotor activity (open field, maze exploration, residential running wheel, residential figure 8 maze), open-field activity response to amphetamine, acoustic startle, prepulse inhibition (PPI) of acoustic startle, juvenile play behavior, anxiety (emergence tests), motor coordination (rotarod performance), spatial learning (Morris water maze and food-reinforced complex maze), and operant performance (time estimation and response inhibition) were assessed in male rats. Body weight was decreased beginning at PND 43 until sacrifice on PND 127. Whole and regional brain weights were less, especially hippocampus, cerebellum, brainstem, and cortical remnant. Indications of delayed development were apparent; specifically, DEX-treated rats took significantly longer to turn on PND 8, but not PND 9, in the negative geotaxis test. DEX treatment induced deficits in the Morris water maze that were similar to hippocampal deficits. Open-field activity changes were inconsistent; however, DEX-treated rats were hyperactive during the dark period in running wheel tests. There were no indications of changes in reactivity or emotionality.