Bilateral high-frequency stimulation of the subthalamic nucleus on attentional performance: transient deleterious effects and enhanced motivation in both intact and parkinsonian rats.

It is now well established that subthalamic nucleus high-frequency stimulation (STN HFS) alleviates motor problems in Parkinson's disease. However, its efficacy for cognitive function remains a matter of debate. The aim of this study was to assess the effects of STN HFS in rats performing a visual attentional task. Bilateral STN HFS was applied in intact and in bilaterally dopamine (DA)-depleted rats. In all animals, STN HFS had a transient debilitating effect on all the variables measured in the task. In DA-depleted rats, STN HFS did not alleviate the deficits induced by the DA lesion such as omissions and latency to make correct responses, but induced perseverative approaches to the food magazine, an indicator of enhanced motivation. In sham-operated controls, STN HFS significantly reduced accuracy and induced perseverative behaviour, mimicking partially the effects of bilateral STN lesions in the same task. These results are in line with the hypothesis that STN HFS only partially mimics inactivation of STN produced by lesioning and confirm the motivational exacerbation induced by STN inactivation.

Using a runway paradigm to assess the relative strength of rats' motivations for enrichment objects

Laboratory animals should be provided with enrichment objects in their cages; however, it is first necessary to test whether the proposed enrichment objects provide benefits that increase the animals’ welfare. The two main paradigms currently used to assess proposed enrichment objects are the choice test, which is limited to determining relative frequency of choice, and consumer demand studies, which can indicate the strength of a preference but are complex to design. Here, we propose a third methodology: a runway paradigm, which can be used to assess the strength of an animal’s motivation for enrichment objects, is simpler to use than consumer demand studies, and is faster to complete than typical choice tests. Time spent with objects in a standard choice test was used to rank several enrichment objects in order to compare with the ranking found in our runway paradigm. The rats ran significantly more times, ran faster, and interacted longer with objects with which they had previously spent the most time. It was concluded that this simple methodology is suitable for measuring rats’ motivation to reach enrichment objects. This can be used to assess the preference for different types of enrichment objects or to measure reward system processes.

Cannabis constituents modulate ∆9-tetrahydrocannabinol-induced hyperphagia in rats

Rationale The hyperphagic effect of ∆9-tetrahydrocannabinol (∆9THC) in humans and rodents is well known. However, no studies have investigated the importance of ∆9THC composition and any influence other non-∆9THC cannabinoids present in Cannabis sativa may have. We therefore compared the effects of purified ∆9THC, synthetic ∆9THC (dronabinol), and ∆9THC botanical drug substance (∆9THC-BDS), a ∆9THC-rich standardized extract comparable in composition to recreationally used cannabis. Methods Adult male rats were orally dosed with purified ∆9THC, synthetic ∆9THC, or ∆9THC-BDS, matched for ∆9THC content (0.34–2.68 mg/kg). Prior to dosing, subjects were satiated, and food intake was recorded following ∆9THC administration. Data were then analyzed in terms of hourly intake and meal patterns. Results All three ∆9THC substances tested induced significant hyperphagic effects at doses ≥0.67 mg/kg. These effects included increased intake during hour one, a shorter latency to onset of feeding and a greater duration and consumption in the first meal. However, while some differences in vehicle control intakes were observed, there were significant, albeit subtle, differences in pattern of effects between the purified ∆9THC and ∆9THC-BDS. Conclusion All ∆9THC compounds displayed classical ∆9THC effects on feeding, significantly increasing short-term intake whilst decreasing latency to the first meal. We propose that the subtle adjustment to the meal patterns seen between the purified ∆9THC and ∆9THC-BDS are due to non-∆9THC cannabinoids present in ∆9THC-BDS. These compounds and other non-cannabinoids have an emerging and diverse pharmacology and can modulate ∆9THC-induced hyperphagia, making them worth further investigation for their therapeutic potential.

Relationship between resistance factors and treatment efficacy when bromadiolone was used against anticoagulant-resistant Norway rats (Rattus norvegicus Berk.) in Wales

We investigated the relationship between the severity and incidence of resistance among Norway rats (Rattus norvegicus) on a farm in Wales and the subsequent outcome of a practical rodent control operation. Bromadiolone resistance factors were estimated for rats trapped on the farm using the blood clotting response test, and were found to be 2 to 3 for male rats and approximately 6 for females. The incidence of resistance in the rat population was high. Infestation size was estimated by census baiting and tracking, and was found to be substantial, with a maximum of 6.5 kg of bait being eaten on a single night. A proprietary rodenticide (Deadline (TM)), containing 0.005% bromadiolone, was used to control the infestation. The duration of baiting was 35 days and, according to the two methods of assessment used, treatment success was in the region of 87 and 93%. No evidence was observed of a significant impact of resistance on the rat control operation, and the remaining rats of this very heavy infestation would probably have been controlled if baiting had continued for longer.

Susceptibility to the anticoagulants bromadiolone and coumatetralyl in wild Norway rats (Rattus norvegicus) from the UK and Germany

A new blood clotting response test was used to determine the susceptibility, to coumatetralyl and bromadiolone, of laboratory strains of Norway rat from Germany and the UK (Hampshire), and wild rats trapped on farms in Wales (UK) and Westphalia (Germany). Resistance factors were calculated in relation to the CD strain of Norway rat. An outbred strain of wild rats, raised from rats trapped in Germany, was found to be more susceptible to coumatetralyl by a factor of 0.5-0.6 compared to the CD strain. Homozygous and heterozygous animals of a strain of resistant rats from Westphalia were cross-resistant to coumatetralyl and bromadiolone, with a higher resistance factor for bromadiolone than that found in both UK strains. Our results show that the degree of altered susceptibility and resistance varies between strains of wild rat and between resistance foci. Some wild rat strains may be more susceptible than laboratory rat strains. Even in a well-established resistance area, it may be difficult to find infestations with resistance high enough to suspect control problems with bromadiolone, even after decades of use of this compound.

Influence of plant and bacterial myrosinase activity on the metabolic fate of glucosinolates in gnotobiotic rats

The breakdown of glucosinolates, a group of thioglucoside compounds found in cruciferous plants, is catalysed by dietary or microbial myrosinase. This hydrolysis releases a range of breakdown products among which are the isothiocyanates, which have been implicated in the cancer-protective effects of cruciferous vegetables. The respective involvement of plant myrosinase and gut bacterial myrosinase in the conversion, in vivo, of glucosinolates into isothiocyanates was investigated in sixteen Fischer 344 rats. Glucosinolate hydrolysis in gnotobiotic rats harbouring a whole human faecal flora (Flora+) was compared with that in germ-free rats (Flora-). Rats were offered a diet where plant myrosinase was either active (Myro+) or inactive (Myro-). The conversion of prop-2-enyl glucosinolate and benzyl glucosinolate to their related isothiocyanates, allyl isothiocyanate and benzyl isothiocyanate, was estimated using urinary mercapturic acids, which are endproducts of isothiocyanate metabolism. The highest excretion of urinary mercapturic acids was found when only plant myrosinase was active (Flora-, Myro+ treatment). Lower excretion was observed when both plant and microbial myrosinases were active (Flora+, Myro+ treatment). Excretion of urinary mercapturic acids when only microbial myrosinase was active (Flora+, Myro- treatment) was low and comparable with the levels in the absence of myrosinase (Flora-, Myro- treatment). No intact glucosinolates were detected in the faeces of rats from the Flora+ treatments confirming the strong capacity of the microflora to break down glucosinolates. The results confirm that plant myrosinase can catalyse substantial release of isothiocyanates in vivo. The results also suggest that the human microflora may, in some circumstances, reduce the proportion of isothiocyanates available for intestinal absorption.

Absorption, tissue distribution and excretion of pelargonidin and its metabolites following oral administration to rats

Recent reports have demonstrated various cardiovascular and neurological benefits associated with the consumption of foods rich in anthocyanidins. However, information regarding absorption, metabolism, and especially, tissue distribution are only beginning to accumulate. In the present study, we investigated the occurrence and the kinetics of various circulating pelargonidin metabolites, and we aimed at providing initial information with regard to tissue distribution. Based on HPLC and LC-MS analyses we demonstrate that pelargonidin is absorbed and present in plasma following oral gavage to rats. In addition, the main structurally related pelargonidin metabolite identified in plasma and urine was pelargonidin glucuronide. Furthermore, p-hydroxybenzoic acid, a ring fission product of pelargonidin, was detected in plasma and urine samples obtained at 2 and 18 h after ingestion. At 2 h post-gavage, pelargonidin glucuronide was the major metabolite detected in kidney and liver, with levels reaching 0.5 and 0.15 nmol pelargonidin equivalents/g tissue, respectively. Brain and lung tissues contained detectable levels of the aglycone, with the glucuronide also present in the lungs. Other tissues, including spleen and heart, did not contain detectable levels of pelargonidin or ensuing metabolites. At 18 h post-gavage, tissue analyses did not reveal detectable levels of the aglycone nor of pelargonidin glucuronides. Taken together, our results demonstrate that the overall uptake of the administered pelargonidin was 18 % after 2 h, with the majority of the detected levels located in the stomach. However, the amounts recovered dropped to 1.2 % only 18 h post-gavage, with the urine and faecal content constituting almost 90 % of the total recovered pelargonidin.

Identification of hepatic molecular mechanisms of action of alpha-tocopherol using global gene expression profile analysis in rats

The recent discovery that vitamin E (VE) regulates gene activity at the transcriptional level indicates that VE may exert part of its biological effects by mechanisms which may be independent of its well-recognised antioxidant function. The objective of this study was the identification of hepatic vitamin E-sensitive genes and examination of the effects of VE on their corresponding biological endpoints. Two groups of male rats were randomly assigned to either a VE-sufficient diet or to a control diet deficient in VE for 290 days. High-density oligonucleotide microarrays comprising over 7000 genes were used to assess the transcriptional response of the liver. Differential gene expression was monitored over a period of 9 months, at four different time-points, and rats were individually profiled. This experimental strategy identified several VE-sensitive genes, which were chronically altered by dietary VE. VE supplementation down-regulated scavenger receptor CD36, coagulation factor IX and 5-alpha-steroid reductase type 1 mRNA levels while hepatic gamma glutamyl-cysteinyl synthetase was significantly up-regulated. Measurement of the corresponding biological endpoints such as activated partial thromboplastin time, plasma dihydrotestosterone and hepatic glutathione substantiated the gene chip data which indicated that dietary VE plays an important role in a range of metabolic processes within the liver. (C) 2004 Elsevier B.V. All rights reserved.

Comparison of the antidiabetic activity of Berberis lyceum root extract and berberine in alloxan-induced diabetic rats

Berberine has been shown to have hypoglycaemic activity in several in vitro and in vivo models, although the mechanism of action is not fully known. Berberis lyceum Royle root produces high concentrations of berberine, and in traditional medicine, the whole extract of this plant is used widely to treat diabetes. The antidiabetic activity of the ethanol root extract of Berberis lyceum was compared with pure berberine in normal and alloxan-diabetic rats using similar doses of each. The concentration of berberine in the extract was determined to be 80% dry weight with only trace amounts of other alkaloids present. The purpose of the study was to investigate the effects of berberine and a whole extract of Berberis lyceum on blood glucose and other parameters associated with diabetes, to compare the effects of the crude extract with those of pure berberine and thus validate its use as a therapeutic agent, and finally to identify any contribution of the other components of the extract to these effects. Oral administration of 50 mg/kg of Berberis extract and berberine to normal and experimental diabetic rats produced a significant (p < 0.05) reduction in blood glucose levels from days 3-7 days of treatment. Significant effects were also observed on the glucose tolerance, glycosylated haemoglobin, serum lipid profiles and body weight of experimental animals. Berberis extract and berberine demonstrated similar effects on all parameters measured, and although the extract was comparable in efficacy to berberine, it did not produce any effects additional to those shown by pure berberine. The results support the use of the extract in traditional medicine, and demonstrate that apart from being a highly cost-effective means of treating with berberine, the total extract does not appear to confer any additional benefits or disadvantages compared with the pure compound. Copyright (c) 2008 John Wiley & Sons, Ltd.

The effect of the functional attributes of objects within the caged environment on interaction time in laboratory rats

Determining rat preferences for, and behaviour towards, environmental enrichment objects allows us to provide evidence-based information about how the caged environment may be enriched. In recent years there have been many studies investigating the preferences of laboratory rodents for a wide variety of environmental enrichment objects and materials. While these have provided important information regarding the animals' perception of the items, very few studies have attempted to systematically investigate the precise attributes that constitute a preferred object and the behaviour that these objects afford. We have designed a research program to systematically study rats' motivation to interact with enrichment objects. Here we present the results from two experiments which examined the time rats spent with objects that only differed in size. This showed that rats spent longer with large objects rather than small ones, even though objects were presented individually. We also investigated the rats' behaviour with the objects in an open field and found that rats spent longer climbing on top of the large object. This behaviour continued when the large objects were laid on their sides instead of placed upright in the arena, suggesting that the rats were not simply climbing on the objects to investigate the top of the arena and thus an escape route, but instead were genuinely motivated to climb. This suggests that rat welfare could be enhanced by the addition to their cages of objects that permit climbing. (C) 2009 Elsevier B.V. All rights reserved.

The role of perirhinal cortex in visual discrimination learning for visual secondary reinforcement in rats

Perirhinal cortex in monkeys has been thought to be involved in visual associative learning. The authors examined rats' ability to make associations between visual stimuli in a visual secondary reinforcement task. Rats learned 2-choice visual discriminations for secondary visual reinforcement. They showed significant learning of discriminations before any primary reinforcement. Following bilateral perirhinal cortex lesions, rats continued to learn visual discriminations for visual secondary reinforcement at the same rate as before surgery. Thus, this study does not support a critical role of perirhinal cortex in learning for visual secondary reinforcement. Contrasting this result with other positive results, the authors suggest that the role of perirhinal cortex is in "within-object" associations and that it plays a much lesser role in stimulus-stimulus associations between objects.

Soya phytoestrogens change cortical and hippocampal expression of BDNF mRNA in male rats

Adult male hooded Lister rats were either fed a diet containing 150 microg/g soya phytoestrogens or a soya-free diet for 18 days. This concentration of phytoestrogens should have been sufficient to occupy the oestrogen-beta, but not the oestrogen-alpha, receptors. Using in situ hybridisation, significant reductions were found in brain-derived neurotrophic factor (BDNF) mRNA expression in the CA3 and CA4 region of the hippocampus and in the cerebral cortex in the rats fed the diet containing phytoestrogens, compared with those on the soya-free diet. No changes in glutamic acid decarboxylase-67 or glial fibrillary acidic protein mRNA were found. This suggests a role for oestrogen-beta receptors in regulating BDNF mRNA expression.

Anticoagulant resistance in Norway rats (Rattus norvegicus Berk.) in Kent - a VKORC1 single nucleotide polymorphism, tyrosine139phenylalanine, new to the UK

A sample of 10 Norway rats (Rattus norvegicus) was taken for DNA resistance testing from an agricultural site in Kent where applications of the anticoagulant rodenticide bromadiolone had been unsuccessful. All animals tested were homozygous for the single nucleotide VKORC1 polymorphism tyrosine139phenylalanine, or Y139F. This is a common resistance mutation found extensively in France and Belgium but not previously in the UK. Y139F confers a significant level of resistance to first-generation anticoagulants, such as chlorophacinone, and to the second-generation compound bromadiolone. Another compound widely used in the UK, difenacoum, is also thought to be partially resisted by rats which carry Y139F. A silent VKORC1 mutation was also found in all rats tested. The presence of a third important VKORC1 mutation which confers resistance to anticoagulant rodenticides in widespread use in the UK, the others being Y139C and L120Q, further threatens the ability of pest control practitioners to deliver effective rodent control.

Effects of tamper-resistant bait boxes on bait uptake by Norway rats (Rattus norvegicus Berk.)

We compared the quantity of wheat bait consumed by Norway rats (Rattus norvegicus) from: (i) wooden bait trays, made as safe as possible from non-target animals using materials available at trial sites, and (ii) three different, proprietary tamper-resistant rat bait boxes. A balanced Latin square experimental design was used to overcome operational biases that occur when baits of different types are applied simultaneously at the same sites. The consumption of bait from the four different types of bait placement differed significantly and accounted for more than 76% of the total variation. The amount of bait eaten by rats from the bait trays was approximately eight times greater than the quantity eaten from the tamper-resistant bait boxes. The three bait box designs appeared to deter bait consumption by rats to a similar extent. Tamper-resistant bait boxes are essential tools in the application of rodenticides in many circumstances but their use should not be mandatory when it is possible to make baits safe from non-target animals by other means.

A low delta-9-tetrahydrocannabinol cannabis extract induces hyperphagia in rats

Appetite stimulation via partial agonism of cannabinoid type 1 receptors by Δ9tetrahydrocannabinol (Δ9THC) is well documented and can be modulated by non-Δ9THC phytocannabinoids. Δ9THC concentrations sufficient to elicit hyperphagia induce changes to both appetitive (reduced latency to feed) and consummatory (increased meal one size and duration) behaviours. Here, we show that a cannabis extract containing too little Δ9THC to stimulate appetite can induce hyperphagia solely by increasing appetitive behaviours. Twelve, male Lister hooded rats were presatiated before treatment with a low-Δ9THC cannabis extract (0.5, 1.0, 2.0 and 4.0 mg/kg). Hourly intake and meal pattern data were recorded and analyzed using one-way analyses of variance followed by Bonferroni post-hoc tests. The cannabis extract significantly increased food intake during the first hour of testing (at 4.0 mg/kg) and significantly reduced the latency to feed versus vehicle treatments (at doses ≥1.0 mg/kg). Meal size and duration were unaffected. These results show only the increase in appetitive behaviours, which could be attributed to non-Δ9THC phytocannabinoids in the extract rather than Δ9THC. Although further study is required to determine the constituents responsible for these effects, these results support the presence of non-Δ9THC cannabis constituent(s) that exert a stimulatory effect on appetite and likely lack the detrimental psychoactive effects of Δ9THC.