First Hour Of Testing Research Articles

Antifungal Activity, Mode of Action, and Cytotoxicity of 4-Chlorobenzyl p-Coumarate: A Promising New Molecule.

Fungal infections represent a serious health problem worldwide. The study evaluated the antifungal activity of 4-chlorobenzyl p-coumarate, an unprecedented semi-synthetic molecule. Docking molecular and assay experiments were conducted to determine the Minimum Inhibitory Concentration (MIC) and Minimum Fungicidal Concentration (MFC), mode of action, effect on growth, fungal death kinetics, drug association, effects on biofilm, micromorphology, and against human keratinocytes. The investigation included 16 strains of Candida spp, including C. albicans, C. krusei, C. glabrata, C. tropicalis, C. dubliniensis, C. lusitaniae, C. utilis, C. rugosa, C. guilhermondi, and C. parapsilosis. Docking analysis predicted affinity between the molecule and all tested targets. MIC and MFC values ranged from 3.9 μg/mL (13.54 μM) to 62.5 μg/mL (217.01 μM), indicating a probable effect on the plasma membrane. The molecule inhibited growth from the first hour of testing. Association with nystatin proved to be indifferent. All concentrations of the molecule reduced fungal biofilm. The compound altered fungal micromorphology. The tested compound exhibited an IC50 of 7.90±0.40 μg/mL (27.45±1.42 μM) for keratinocytes. 4-chlorobenzyl p-coumarate showed strong fungicidal effects, likely through its action on the plasma membrane and alteration of fungal micromorphology, and mildly cytotoxic to human keratinocytes.

Highly Dispersed Few-Nanometer Chlorine-Doped SnO2 Catalyst Embedded in a Polyaniline Matrix for Stable HCOO- Production in a Flow Cell.

With the spread of alternative energy plants, electrolysis processes are becoming the protagonists of the future industrial generation. The technology readiness level for the electrochemical reduction of carbon dioxide is still low and is largely based on precious metal resources. In the present work, tin ions are anchored on a polyaniline matrix, via a sonochemical synthesis, forming a few atomic layers of chlorine-doped SnO2 with a total loading of tin atom load of only 7 wt %. This catalyst is able to produce formate (HCOO–) with great selectivity, exceeding 72% of Faradaic efficiency in the first hour of testing in 1 M KHCO3 electrolyte, with a current density of more than 50 mA cm–2 in a 2 M KHCO3 electrolyte flow cell setup. Catalyst stability tests show a stable production of HCOO– during 6 h of measurement, accumulating an overall TONHCOO– of more than 10,000 after 16 h of continuous formate production. This strategy is competitive in drastically reducing the amount of metal required for the overall catalysis.

Fe-doped olivine and char for in-bed elimination of gasification tars in an air-blown fluidised bed reactor coupled with oxidative hot gas filtration

Gasification experiments were carried out in a pilot scale fluid bed reactor operated under allothermal mode and low fluidisation regime with iron-doped olivine and char as catalyst for in-situ tar abatement.The catalyst combination resulted in a reduction of 50% in the overall tar yield with respect to the reference values. Furthermore, the integration of an oxidative Hot Gas Filtration unit downstream the gasification reactor led to a further reduction in overall tar yield and relatively clean gas was obtained (approx. 1 g/Nm3, benzene-free). The tar dew point of the resulting producer gas was estimated to 80 °C, only 40 °C above the threshold value recommended for its valorisation in standard internal combustion engines. Moreover, catalyst elutriation and char hold-up took place to a large extent inside the reactor. The analysis of catalyst samples at different Time-On-Stream (TOS) revealed: (i) a considerable loss of iron oxides during the first hour of test because of the interparticle mechanical attrition (mostly surface abrasion) and partial reduction of hematite to magnetite and wustite but, stable composition at higher TOS, (ii) the loss of the iron oxide coverage of Fe/olivine particles and the formation of agglomerates with increasing TOS and, (iii) the amount of carbon deposited in the surface of the Fe/olivine particles increased with TOS, but in any case, these carbon deposits can be completely oxidized above 650 °C.

Captive great apes tend to innovate simple tool behaviors quickly.

Recent studies have highlighted the important role that individual learning mechanisms and different forms of enhancenment play in the acquisition of novel behaviors by naïve individuals. A considerable subset of these studies has focused on tool innovation by our closest living relatives, the great apes, to better undestand the evolution of technology in our own lineage. To be able to isolate the role that individual learning plays in great ape tool innovation, researchers usually employ what are known as baseline tests. Although these baselines are commonly used in behavioral studies in captivity, the length of these tests in terms of number of trials and duration remains unstandarized across studies. To address this methodological issue, we conducted a literature review of great ape tool innovation studies conducted in zoological institutions and compiled various methodological data including the timing of innovation. Our literature review revealed an early innovation tendency in great apes, which was particularly pronounced when simple forms of tool use were investigated. In the majority of experiments where tool innovation took place, this occurred within the first trial and/or the first hour of testing. We discuss different possible sources of variation in the latency to innovate such as testing setup, species and task. We hope that our literature review helps researchers design more data-informed, resource-efficient experiments on tool innovation in our closest living relatives.

Development of thermoresponsive poloxamer in situ gel loaded with gentamicin sulfate for cavity wounds

Poloxamer hydrogels are thermoresponsive hydrogels that become fluid when cooled and gel-like when heated. Adding poloxamer 188 to a poloxamer 407 solution increases the overall gelation temperature, thereby allowing adjustments to the window of operating temperatures. The rheological properties of the poloxamer hydrogel, including gelation temperature and gelation time, were investigated, and the biocompatibility, drug release, and antibacterial properties of a gentamicin-loaded hydrogel were determined. An injectable hydrogel was successfully formulated using 20 wt% of poloxamer 407 and 3 wt% of poloxamer 188. This system became fluid at room temperature (25 °C) in the presence of deionized water; at human body temperature (37 °C), it changed to a gel-like state. The gelation time was approximately 95 seconds. The poloxamer hydrogels showed no cytotoxicity to L929 cells after seven days of culturing. A poloxamer hydrogel loaded with gentamicin sulfate, an antibiotic, was studied for its antibacterial properties against E. coli, B. cereus, S. aureus, and MRSA using gentamicin solution as the control. The results showed that the gentamicin-loaded poloxamer hydrogel inhibited bacteria from the first hour of testing. Moreover, the zone of inhibition of the gentamicin-loaded poloxamer hydrogel was larger than that of the gentamicin solution for a similar concentration of gentamicin sulfate. It can be a potent drug carrier for infected cavity wounds.

The production and application of carbon nanomaterials from high alkali silicate herbaceous biomass

Herein, value-added materials such as activated carbon and carbon nanotubes were synthesized from low-value Miscanthus × giganteus lignocellulosic biomass. A significant drawback of using Miscanthus in an energy application is the melting during the combustion due to its high alkali silicate content. An application of an alternative approach was proposed herein for synthesis of activated carbon from Miscanthus × giganteus, where the produced activated carbon possessed a high surface area and pore volume of 0.92 cm3.g−1 after two activation steps using phosphoric acid and potassium hydroxide. The SBET of the raw biomass, after first activation and second activation methods showed 17, 1142 and 1368 m2.g−1, respectively. Transforming this otherwise waste material into a useful product where its material properties can be utilized is an example of promoting the circular economy by valorising waste lignocellulosic biomass to widely sought-after high surface area activated carbon and subsequently, unconventional multi-walled carbon nanotubes. This was achieved when the activated carbon produced was mixed with nitrogen-based material and iron precursor, where it produced hydrophilic multi-wall carbon nanotubes with a contact angle of θ = 9.88°, compared to the raw biomass. synthesised materials were tested in heavy metal removal tests using a lead solution, where the maximum lead absorption was observed for sample AC-K, with a 90% removal capacity after the first hour of testing. The synthesis of these up-cycled materials can have potential opportunities in the areas of wastewater treatment or other activated carbon/carbon nanotube end uses with a rapid cycle time.

Production and characterisation of activated carbon and carbon nanotubes from potato peel waste and their application in heavy metal removal.

Herein, activated carbon (AC) and carbon nanotubes (CNTs) were synthesised from potato peel waste (PPW). Different ACs were synthesised via two activation steps: firstly, with phosphoric acid (designated PP) and then using potassium hydroxide (designated PK). The AC produced after the two activation steps showed a surface area as high as 833 m2 g−1 with a pore volume of 0.44 cm3 g−1, where the raw material of PPW showed a surface area < 4 m2 g−1. This can help aid and facilitate the concept of the circular economy by effectively up-cycling and valorising waste lignocellulosic biomass such as potato peel waste to high surface area AC and subsequently, multi-walled carbon nanotubes (MWCNTs). Consequently, MWCNTs were prepared from the produced AC by mixing it with the nitrogen-based material melamine and iron precursor, iron (III) oxalate hexahydrate. This produced hydrophilic multi-wall carbon nanotubes (MWCNTs) with a water contact angle of θ = 14.97 °. Both AC and CNT materials were used in heavy metal removal (HMR) where the maximum lead absorption was observed for sample PK with a 84% removal capacity after the first hour of testing. This result signifies that the synthesis of these up-cycled materials can have applications in areas such as wastewater treatment or other conventional AC/CNT end uses with a rapid cycle time in a two-fold approach to improve the eco-friendly synthesis of such value-added products and the circular economy from a significant waste stream, i.e., PPW.Graphical abstract.

The protective effects of the melanocortin receptor (MCR) agonist, melanotan-II (MTII), against binge-like ethanol drinking are facilitated by deletion of the MC3 receptor in mice

Recent data have implicated the melanocortin (MC) system in modulating voluntary ethanol consumption. Administration of melanotan-II (MTII), a nonselective melanocortin receptor (MCR) agonist, reduces voluntary ethanol consumption in C57BL/6J mice. Previous studies have demonstrated that central infusion of MTII effectively reduced voluntary ethanol drinking in mutant mice lacking normal expression of MC3R (MC3R−/− mice) but failed to alter ethanol drinking in mice lacking expression of MC4R, demonstrating that central MTII administration reduces voluntary ethanol drinking by signaling through the MC4R. However, evidence shows that the neurocircuitry recruited during excessive binge-like ethanol drinking versus moderate ethanol drinking are not identical. Thus the present study sought to investigate the potential role of the MC3R in binge-like ethanol intake. To this end, the “drinking in the dark” (DID) procedure, a commonly used animal model of binge-like ethanol drinking, was employed. Wild-type MC3R+/+ and MC3R−/− mice were given intracerebroventricular (i.c.v.) infusion of MTII (0.0, 0.25, 0.50, or 1.0μg) prior to the onset of a 4-h testing period in which mice were given access to 20% (v/v) ethanol. Immediately after the 4-h testing period, tail blood samples were collected from each animal in order to assess blood ethanol concentrations (BECs). Consistent with previous findings, central administration of MTII blunted binge-like ethanol drinking in both MC3R+/+ and MC3R−/− mice. Interestingly, all doses of MTII blunted binge-like ethanol drinking in MC3R−/− mice during the first hour of testing, while only the 1.0μg dose reduced binge-like drinking in MC3R+/+ mice. Thus, MC3R−/− mice were more sensitive to the protective effects of MTII. These data suggest that MC3Rs oppose the protective effects of MTII against binge-like ethanol drinking, and thus selective MC3R antagonists may have potential therapeutic roles in treating excessive ethanol drinking.

A low-Δ9tetrahydrocannabinol cannabis extract induces hyperphagia in rats

Appetite stimulation via partial agonism of cannabinoid type 1 receptors by Δtetrahydrocannabinol (ΔTHC) is well documented and can be modulated by non-ΔTHC phytocannabinoids. ΔTHC 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 ΔTHC to stimulate appetite can induce hyperphagia solely by increasing appetitive behaviours. Twelve, male Lister hooded rats were presatiated before treatment with a low-ΔTHC 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-ΔTHC phytocannabinoids in the extract rather than ΔTHC. Although further study is required to determine the constituents responsible for these effects, these results support the presence of non-ΔTHC cannabis constituent(s) that exert a stimulatory effect on appetite and likely lack the detrimental psychoactive effects of ΔTHC.

Age-related differences in auditory evoked responses during rapid perceptual learning

Objective Young and older adults can learn to rapidly discriminate between elementary visual and auditory features. While growing evidence supports the notion that such behavioral improvement is paralleled by neuroplastic changes in corresponding sensory areas during adulthood, studies have not examined practice-related improvement in older adults and the corresponding changes in neural activity. Methods We used event-related potentials (ERPs) to investigate the effects of age on rapid learning-related changes in listeners’ ability to identify two phonetically different vowels presented simultaneously. Results During the first hour of testing, young and older listeners showed comparable behavioral improvement in identifying both vowels. In young adults, learning was paralleled by enhanced amplitudes of early (130 ms) and late (320 ms) ERP waves over the right temporal lobe, as well as an increased negative wave over the midline parietal region, peaking at about 400 ms after sound onset. The practice-related changes over the right temporal lobe were not present in older adults whereas the learning effect observed over the parietal region was present in both young and older adults. In older adults, behavioral improvement was also associated with reduced N1 amplitude recorded at inferior and posterior temporal/occipital scalp sites while no such changes were observed in young adults. Conclusions Age-related differences in neural activity during learning suggest that neural networks supporting behavioral improvements in speech segregation and identification change during the course of aging. Significance This research highlights the role of practice on concurrent sound perception and may facilitate the development of training programs that may help older listeners to parse the auditory scene into component sound sources.

Changes in Auditory Cortex Parallel Rapid Perceptual Learning

Learning perceptual skills is characterized by rapid improvements in performance within the first hour of training (fast perceptual learning) followed by more gradual improvements that take place over several daily practice sessions (slow perceptual learning). Although it is widely accepted that slow perceptual learning is accompanied by enhanced stimulus representation in sensory cortices, there is considerable controversy about the neural substrates underlying early and rapid improvements in learning perceptual skills. Here we measured event-related brain potentials while listeners were presented with 2 phonetically different vowels. Listeners' ability to identify both vowels improved gradually during the first hour of testing and was paralleled by enhancements in an early evoked response ( approximately 130 ms) localized in the right auditory cortex and a late evoked response ( approximately 340 ms) localized in the right anterior superior temporal gyrus and/or inferior prefrontal cortex. These neuroplastic changes depended on listeners' attention and were preserved only if practice was continued; familiarity with the task structure (procedural learning) was not sufficient. We propose that the early increases in cortical responsiveness reflect goal-directed changes in the tuning properties of auditory neurons involved in parsing concurrent speech signals. Importantly, the neuroplastic changes occurred rapidly, demonstrating the flexibility of human speech segregation mechanisms.

Locomotor suppressive and anxiolytic-like effects of urocortin 3, a highly selective type 2 corticotropin-releasing factor agonist

Murine urocortin 3 (mUcn 3), a member of the corticotropin releasing factor (CRF) peptide family, was recently identified. Of known agonists, this neuropeptide displays the highest degree of selectivity in binding to the CRF 2 receptor. These experiments sought to test the hypothesis that CRF 2 receptors have a role in modulating stress by examining intracerebroventricular (i.c.v.) administration of mUcn 3 in animal models of activation and anxiety. To investigate the effects of mUcn 3 on motor activity, rats were injected with mUcn 3 (0, 0.1, 1.0 or 10 μg, i.c.v.) 10 min prior to testing and activity was monitored for 6 h. To determine changes in novelty-induced exploration, rats were injected with mUcn 3 (0, 0.1, 1.0 or 10 μg, i.c.v.) 10 min prior to testing and examined in the elevated plus maze. Finally, delayed effects of mUcn 3 were tested in rats injected with 1.0 μg of mUcn 3 or vehicle 30 or 60 min prior to testing in the elevated plus maze. Injections of mUcn 3 significantly decreased locomotor activity in rats during the first hour of testing. In the elevated plus maze, mUcn 3 injections significantly increased open arm preference compared to vehicle when tested using a 10-min pretreatment interval. mUcn treated rats tested in the elevated plus maze following the delayed pretreatment interval did not differ from controls. These data demonstrate that injection of mUcn 3 leads to acute locomotor suppressive effects and decreases in stress-like behaviors, indicating an anxiolytic-like action for mUcn 3, and suggests a possible role of the CRF 2 receptor in the regulation of stress-related behavior.

Automated measurement of age-related changes in the locomotor response to environmental novelty and home-cage activity

The likelihood to explore in an open-field environment decreases with age. Older animals tend to be less active and explore less both in novel and home-cage environments. The locomotor performance (fine movements, ambulatory movements, and rearing) of male Fischer 344 (F344) rats that were 6 ( n=6) or 22 ( n=6) months of age was evaluated by continuous automated counting of photobeam interruptions, every 30 min, during 60 consecutive hours, in standard polycarbonate cages. Novel environment performance was determined by photobeam interruption counting during the first hour in the new cage. The remaining 59 h were evaluated as home-cage activity. A significant age-related decrease in ambulatory and fine motor activity was seen during the first hour of testing (novel environment). In addition, aged rats showed a decreased number of ambulatory and fine movements in home-cage activity, predominately during the dark portion of the light cycle and during or around both light-switch periods (05:00 and 17:00). No differences were seen in rearing behavior. These findings provide a more detailed analysis and additional evidence of the activity decreases and rhythmic changes seen in aged F344 rats under uninterrupted testing conditions.

Commercially available folic acid supplements and their compliance with the British Pharmacopoeia test for dissolution.

A recent report suggested that some folic acid preparations available in the United States failed to meet the specifications for dissolution specified by the US Pharmacopoeia (USP), of 70 per cent drug release in the first hour of testing. The Teratology Society recommends that women of childbearing age should take a daily supplement of 400 microg folic acid when they are trying to conceive, to reduce the risk of foetal neural tube defects. The consequence of this failure to meet the USP requirements may be that an inadequate dose of folate may be absorbed and thus the expected level of protection against neural tube defects not afforded. The purpose of the present study was to examine a number of brands of folic acid (400 microg), available commercially in the United Kingdom, for compliance with the British Pharmacopoeia (BP) test for dissolution. Ten tablets (or capsules) from each of 11 brands were tested using dissolution apparatus compliant with BP requirements, using 0.1 M sodium hydroxide as the dissolution medium. The results indicated that four of the brands failed to release 70 per cent of the nominal drug content in the first hour of test and thus did not comply with the test. Two of the seven brands that passed the test went on to release more than 150 per cent of the nominal 400 microg drug content. These results highlight the problems of dose uniformity and the potential health risks of slow dissolution and under-dosing in commercially available folic acid dosage forms.

Social influences on the amount of food eaten by Norway rats

A naive observer Norway rat offered a choice between two foods, after it interacts with a demonstrator rat fed one of those foods, increases its preference for whichever food the demonstrator rat ate. It is not known whether interaction with a demonstrator rat would also increase the amount that an observer rat would eat if it were given access only to the food the demonstrator had eaten. In this study, each observer rat interacted with a demonstrator rat fed a food, either familiar or unfamiliar to the observer, and the observer was then offered a weighed sample of the food that the demonstrator had eaten. It was found that, during the first hour of testing, observer rats that had interacted with demonstrators fed an unfamiliar food, increased their intake of that food roughly four-fold. Observer rats that interacted with demonstrator rats fed a familiar food however, did not increase their food intake. Socially enhanced intake of unfamiliar food was seen only during the first hour that observers had access to food and was compensated for during the next 23h of feeding. This short-term increase in observer intake of unfamiliar foods appeared to result from socially-induced motivation to ingest unfamiliar foods rather than from socially-induced reduction in neophobia.

Neuronal Fos activation in olfactory bulb and forebrain of male rats having erections in the presence of inaccessible estrous females

Volatile odors from estrous female rats are necessary and sufficient to induce non-contact penile erections in male rats. It is not known whether these pheromones are detected by the accessory as opposed to the main olfactory system or whether they are processed by forebrain regions that receive olfactory inputs. Using nuclear Fos immunoreactivity as a marker of neuronal activation, we asked how the detection and processing of distal cues from inaccessible estrous females, which elicited non-contact penile erections, compared with the processing of sensory cues from soiled estrous bedding which did not elicit non-contact penile erections. In Experiment 1, groups of sexually experienced males were given one of five treatments. A control group was placed on clean bedding. A second group displayed non-contact penile erections when exposed to the smell, sight and sound of an estrous female restrained behind a permeable barrier. A third group was exposed to the same stimuli as the second (an estrous female) but failed to exhibit non-contact penile erections during the first hour of testing. A fourth group was placed on soiled estrous bedding, and a fifth group was allowed two ejaculations with an estrous female. All males were perfused with 4% paraformaldehyde 2 h after the onset of these respective treatments, and their brains were later processed for Fos immunoreactivity. Non-contact penile erections were observed in males that were exposed to distal cues from an estrous female but not in males exposed to soiled estrous bedding. Males that displayed non-contact penile erections or that were exposed to estrous bedding showed significantly more neuronal Fos immunoreactivity than clean-bedding controls in the nucleus accumbens core and shell, anterior and posterior medial amygdala, bed nucleus of the stria terminalis and the medial preoptic nucleus. Even greater neuronal Fos responses occurred in these regions in mated males. In Experiment 2 these same treatments were given to another cohort of sexually experienced males. Increased neuronal Fos immunoreactivity was observed in the granule and mitral cell layers of the accessory olfactory bulb of males that were either mated or exposed to estrous bedding, but not in males that displayed non-contact penile erections in response to distal cues from an estrous female. The volatile odors which presumably caused non-contact penile erections failed to stimulate significant neuronal Fos immunoreactivity in five main olfactory bulb sites examined. Even so, it seems likely that these pheromones are detected via the main olfactory system and are subsequently processed by the same projection circuit that responds to other pheromones present in estrous bedding that are incapable of eliciting non-contact penile erections.

Hyperphagia in pre-fed rats following oral δ 9-THC

WILLIAMS, C.M., P.J. ROGERS AND T.C. KIRKHAM. Hyperphagia in pre-fed rats following oral Δ 9-THC. PHYSIOL BEHAV 65(2) 343–346, 1998.—Using a pre-feed paradigm, the effects of orally-administered Δ 9- tetrahydrocannabinol (THC) on low baseline levels of nocturnal feeding were assessed. Following 2-h access to a palatable wet mash diet at dark onset, adult male Lister hooded rats (Charles River) were treated with either sesame seed oil vehicle or Δ 9- tetrahydrocannabinol (0.063, 0.12, 0.25, 0.5, 1.0, or 2.0 mg/kg). One hour later, rats were allowed ad libitum access to standard chow, and intakes were monitored over the subsequent 24 h. Doses of 0.5, 1.0, and 2.0 mg/kg produced substantial hyperphagia during the first hour of testing. Subsequently, rats compensated for their overconsumption so that 24-h intakes were similar in all conditions. The data confirm anecdotal reports of the orexigenic actions of exogenous cannabinoids and suggest a critical role for endogenous cannabinoid systems in the regulation of appetite .

Selective Antagonist for the Melanocortin 4 Receptor (HS014) Increases Food Intake in Free-Feeding Rats

Recently, we discovered a cyclic analogue of MSH (melanocyte stimulating hormone), HS014, which is the first selective antagonist of the MC4 receptor. We have here studied the effects of this peptide on food intake in non-deprived male rats. Vehicle or five doses of HS014 (0.1-10 nmol) were administered ICV at midday. HS014 (0.33-3.3 nmol) significantly and in a dose-dependent manner increased food intake for the first 1 h. At 4 h after the injections, food intake was also significantly increased in rats treated with 1 and 3.3 nmol of HS014, whereas the lowest dose tested (0.1 nmol) was without effect. Cumulative food intake increased to 100% at 4 h after the injections. The highest dose of HS014 (10 nmol) induced sedation and inhibited feeding for first hour of testing. However, this dose also increased food consumption later. These data demonstrate that attenuation of central melanocortinergic tone with HS014 induces disinhibition of feeding and provides additional evidence for the hypothesis that activation of the MC4 receptor inhibits food intake. HS014 may be a useful tool for elucidating the role of the MC receptor subtypesin vivo.This is the first report demonstrating an increase in daytime food intake in free-feeding animals caused by a MC receptor active agent.

Sex differences in the locomotor-activating effects of amphetamine: Role of circulating testosterone in adulthood

The effects of circulating testosterone (T) on sex differences in locomotor activity elicited by both acute and repeated amphetamine (AMPH) administration were evaluated in adult rats. Male and female rats were gonadectomized in adulthood and implanted with Silastic capsules containing either T or cholesterol (CHOL). In the preexposure period, locomotor activity in response to IP injections of either AMPH (1.5 or 1.3 mg/kg) or saline (1.0 ml/kg) was measured for 2 h, every third day on five occasions. In a subsequent test for sensitization, all animals received AMPH (0.75 or 0.65 mg/kg). Results indicate that regardless of the presence of circulating T, females showed higher levels of activity in response to AMPH than males. In male animals, T suppressed AMPH-induced activity on the first day of the preexposure period, but this effect was lost with repeated testing. In female animals, T enhanced AMPH-induced activity during the first hour of testing. The presence of circulating T did not influence the degree of sensitization in either sex as determined by the difference between AMPH preexposed and SAL preexposed animals on the test day for sensitization.

Food puzzle for singly caged primates.

To enhance environmental complexity for singly caged pigtailed macaques (Macaca nemestrina), we designed a food puzzle to promote foraging. The puzzles, made of clear plastic tubing and loaded with peanuts in the shell, were suspended from linked chains and attached to the fronts of the cages. Animals manipulated the puzzles by reaching through a cage opening. Upon presentation of loaded puzzles, most animals attempted to remove the peanuts. More peanuts were removed within an hour after the puzzle was loaded than at any other time during the day. Young adult animals showed no sex differences in number of peanuts removed and were more proficient than middle-aged animals in removing peanuts during the first hour of testing. Middle-aged females were more proficient than middle-aged males. The food puzzle enhanced the animals' cage environment by providing a goal-oriented activity that they could control. © 1992 Wiley-Liss, Inc.