Effects of AIT-082, a purine derivative, on tremor induced by arecoline or oxotremorine in mice

The effects of AIT-082, a hypoxanthine derivative, on tremor in mice were investigated. The mice received intragastric administration of AIT-082 for consecutive 60 days at doses of 150, 300 and 600 mg.kg(-1). The results showed that AIT-082 not only effectively inhibited the tremor induced by arecoline or oxotremorine, but also alleviated the tremor intensity and significantly shortened the tremor durations. The inhibition of tremor was perhaps associated with the central cholinergic nerve depressant effects as well as the stimulation of proliferation and differentiation of nerve cells.

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.

AUTOMATED MEASUREMENT OF FREEZING TIME TO CONTEXTUAL AND AUDITORY CUES IN FEAR CONDITIONING AS A SIMPLE SCREENING METHOD TO ASSESS LEARNING AND MEMORY ABILITIES IN RATS

In fear-conditioning paradigms, rats display a freezing response not only upon presentation of a conditioned stimulus (usually tone), but also when returned to a conditioning chamber (context) in which they received an unconditioned stimulus (usually a foot shock). These paradigms have intrinsic advantages for screening effects of chemicals on learning and memory, although the time-consuming monitoring of freezing time by human observers may be problematic. In this study, an automated apparatus was developed to optimize a fear-conditioning paradigm for screening. We developed an apparatus that records freezing time measured from body movements detected by passive infrared (PIR) sensors. The apparatus detected freezing time as accurately as the human scoring method, and these data were used to determine learning parameters (freezing time to context or to tone) and a non-learning parameter (freezing time to novel context) in the rats. Rats orally administered the neurotoxic compound trimethyltin (TMT) exhibited decreased freezing levels to context, but not to tone or to novel context. These results suggest that this automated method can be an effective part of a screening program.

Development of an affordable hi-resolution activity monitor system for laboratory animals

We describe a hardware and software system for recording and analyzing the spatial and temporal pattern of locomotor activity of laboratory animals. The system offers maximal spatial resolution 500-fold greater than existing light beam monitors. An infrared motion analysis systems (MacReflex, Qualysis) simultaneously tracks the location of up to 20 subjects (identified by reflective markers) to within 0.04 mm at a rate of up to 50 Hz. Macintosh software provides measures of distance traveled, amount of area traversed, number of position changes (microevents), average time between movements, number of left and right turns, number of forward movements and reversals, as well as temporal and spatial scaling exponents. This system was validated by comparing these parameters to direct observer scoring of video tapes and other commercially available activity monitors. Our findings show that applying reflective markers to the subjects does not significantly alter activity levels. The effect of pharmacological manipulation with d-amphetamine is provided to show the value of the different activity parameters. The main advantages of this system are very high spatial resolution, capacity to monitoring up to 20 animals simultaneously at reasonable cost, and lack of sensitivity of the system to ambient lighting. The main limitation is the need to apply reflective markers.

Motor function analysis of myelin mutant mice using a rotarod

We have examined motor control in normal and shiverer mutant mice using the rotarod assay, a forced motor activity which tests for balance and co-ordination. Shiverer mice carry a deletion of the myelin basic protein (MBP) gene, resulting in CNS dysmyelination and characteristic motor dysfunction. Homozygous mutant mice had a significant increase in cumulative falls from the rotarod relative to heterozygous mice. Non-acclimated animals of both genotypes showed progressive improvement in performance when tested on successive days. The rotarod test also discriminated shiverer mutants from animals that received gene therapy intervention. Shiverer animals carrying an MBP transgene showed gene-dosage-dependent improvements in motor function, and mutants which received thalamic transplants of wild type oligodendrocyte precursor cells showed improvement relative to sham operated and non-transplanted controls. Thus the rotarod is a sensitive measure of motor function in hypomyelinated mice, and may be useful for assessing the results of experimental manipulations including transgenic gene therapy and cell transplantation.

A revised rotarod procedure for measuring the effect of antinociceptive drugs on motor function in the rat

Tests of putative antinociceptive agents that rely on a motor response of an experimental animal to a noxious stimulus will give false positive results, and may be unethical, if the agent compromises motor function. We report a procedure for measuring potential effects of antinociceptive agents on motor function in the trained rat, using an 80 mm diameter rotarod. Rats were selected for ability to exercise on the rotarod and trained to increasing speeds. In test trials, we measured the time that trained rats could stay on the rod, rotating at 25 rpm, with a cut off at 60 min. Morphine administration decreased rotarod performance significantly at doses of 5.0 mg/kg (P less than 0.05, n = 10) and 7.5 mg/kg (P less than 0.005, n = 10). We also assessed the response to a noxious thermal stimulus by measuring tail flick latency following tail immersion in water at 49 degrees C. A significant dose-dependent increase in tail flick latency was found for dosages of morphine between 2.5 mg/kg and 7.5 mg/kg (P less than 0.005, n = 10). Our rotarod procedure, which incorporates selection, training, and a 60 min trial, provides a sensitive and consistent means of assessing motor function. Our results, implying that morphine indeed compromises motor function in rats at doses at which it is antinociceptive, confirm the necessity for investigating the motor effects of any putative antinociceptive agent.

Effects of mu receptor agonists and droperidol on motor coordination in mice

The effects of morphine, fentanyl, sufentanil and droperidol on motor coordination in mice were studied. Animals were trained to complete successfully the rotarod test before assessing the effects of drugs. Administration of analgesic doses of the mu agonists morphine, fentanyl and sufentanil did not inhibit motor coordination. Droperidol produced a dose related inhibition of motor coordination. When a subthreshold dose of droperidol was administered followed by an opiate, a significant inhibition of motor coordination was observed. The results indicate that although analgesic doses of mu opioid agonists do not affect motor coordination, their combination with droperidol results in motor incoordination. The mechanisms and/or opioid receptor sub-types involved in this in vivo interaction remain to be established.

Spontaneous running in wheels. A microprocessor assisted method for measuring physiological parameters during exercise in rodents

When examining physiological parameters during exercise in rodents most techniques use forced exercise on treadmills or forced swimming which undoubtedly will employ stress to the animals. This paper describes a convenient method to measure physiological parameters during spontaneous exercise in rodents. Hamsters and rats develop a spontaneous running pattern in wheels. The hamsters are reaching maximal activity almost immediately. In contrast, rats increase their running activity with time and need about 4 weeks to reach an average of about 7 km/day. The amount of running is measured by a microprocessor system. With this technique pain threshold, blood pressure and heart rate for example could be measured for extended periods of time, without changing the environment of the animals.

(+)-Amphetamine oral 'drug taking behavior' in naive and tolerant rats

The drinking behavior of naive rats changes predictably in a free choice experiment involving water vs. 0.02%, 0.01% and 0.003% (+)-amphetamine solutions: The higher the concentration of the amphetamine solution, the sooner a number of rats quit drinking it, and the less is ingested by those still drinking it. Physically dependent rats having undergone three withdrawals immediately reject (+)-amphetamine solution in a free choice test with water available. The avoidance of withdrawal symptoms does not motivate further self-administration. Therefore, (+)-amphetamine self-administered in drinking water is neither a reinforcer for naive nor for physically dependent rats in sustaining drug taking behavior. In acute and chronic experiments, the transition from increased motor activity to stereotypical behavior could be demonstrated and evidence was produced that tolerance develops to the (+)-amphetamine-induced increase in motor activity.

An assessment of the spontaneous activity of rats administered morphine, phencyclidine, or nicotine using automated and observational methods

The effects of morphine, phencyclidine, and nicotine on motor activity in rats were characterized using both observational and automated methods. Activity was scored observationally using a time-sampling method that tabulates discrete response categories (still, locomotion, rearing, sniffing, licking, gnawing, head down, swaying, grooming, falling). Behavior was assessed automatically using an activity monitor that records both the time and activity counts spent in large and small (less than 3 cm) movements, rearing, and resting. The following results using male Sprague-Dawley rats represent significant differences from saline-treated controls. Morphine (1-4 mg/kg SC) increased the incidence of locomotion, sniffing, swaying, and grooming depending on the time after drug injection. These changes corresponded to an increase in large and small movement counts and time as measured by the activity monitor. Phencyclidine (1.25-5 mg/kg SC) caused dose-related increases in the incidence of locomotion, sniffing, swaying, and falling, and induced greater large and small activity movement counts and time especially after the 5 mg/kg dose. Nicotine (0.033-0.33 mg/kg SC) decreased the incidence of rearing and increased the frequency of sniffing and grooming. These changes corresponded to a decrease of rearing activity and to a slight increase in small activity. The present data indicate that morphine, phencyclidine, and nicotine exert dose-related and time-related appearances of various categories of behavior in the rat, and that the data from the automated method complement the findings of the direct observational method.

Neurotransmitter receptors in brain regions of acrylamide- treated rats. I: Effects of a single exposure to acrylamide

A single oral dose of acrylamide (25 or 50 mg/kg) increased the level of striatal 3H-spiroperidol binding in six week old male rats. This enhanced dopamine receptor activity was specific since treatment caused no significant changes in glycine, serotonin, and muscarinic cholinergic binding. At the highest acrylamide dose tested (100 mg/kg), elevations of the medullary glycine and frontal cortical serotonin receptors were also found. Pretreatment of animals with a blocker of hepatic mixed function oxidase (SKF 525a) or a thiol blocker (methylmercuric chloride) prevented the acrylamide-induced elevation of striatal spiroperidol binding, indicating that the causative agent was a secondary metabolite of acrylamide. Apomorphine-induced motility was significantly attenuated by 24 hr predosing with acrylamide, suggesting a change in the sensitivity of the dopamine receptor. The behavioral relevance of observed biochemical changes was thus shown by the altered response of treated animals to apomorphine.

3,4,3',4'-Tetrachlorobiphenyl given to mice prenatally produces long-term decreases in striatal dopamine and receptor binding sites in the caudate nucleus

Pregnant CD-1 mice were given 32 mg/kg of 3,4,3',4'-tetrachlorobiphenyl (TCB) or corn oil vehicle, by gavage, on days 10--16 of gestation. At 1 year of age, the offspring were tested for spontaneous motor activity; the mice were then killed and dopamine (DA) levels and specific DA receptor binding were measured in the corpus striatum. Mice exposed to TCB in utero had elevated levels of motor activity, which were associated with decreased DA levels and DA receptor binding sites. The results indicate that in utero exposure to TCB might permanently alter the development of striatal synapses.

Effects of azaperone and acetylpromazine on social and environmental behaviour in sheep

1 Acetylpromazine (Acp, 0.05, 0.1 and 0.5 mg/kg) and azaperone (Azp, 1.0, 1.25 and 1.5 mg/kg) were given by intramuscular injection to separate groups of seven familiar Romney ewes. Thirty minutes after injection the sheep were led into a featureless arena and spatial distribution, activity and shade preference were monitored for 20 min by overhead photography. 2 Behavioural response was complex with both stimulant and depressant effects being seen. The response trends with increasing time for all three measures were significantly different for the two drugs. In particular, Azp tended to increase animal dispersion and Acp to decrease it, in agreement with earlier predictions. 3 The dosage range for Azp was adequate for reduction of individual movement and inter-animal distance but steady state effect was not reached in the time period studied. All doses of Azp initially caused disorientation, as measured by shade preference,, but this improved as sedation deepened. 4 The highest dose of Acp (0.5 mg/kg) achieved steady state effect on individual movement within the study period. The three doses of ACp caused either no change or a slight increase in inter-animal distance. Disorientation with Acp was less and briefer than that seen with Azp.

Sources of variation in locomotor activity and stereotypy in rats treated with d-amphetamine

Rats injected with doses of d-amphetamine 0--5.0 mg/kg were observed continuously in either an enclosed Y-maze or on an elevated Y-shaped platform. Patterns of increased walking and stereotypy were unaffected by the type of apparatus, but rearing remained totally suppressed at all dose levels on the elevated platform. In the second experiment, groups of rats where given single short tests in the enclosed Y-maze, which was novel to them. The stimulant actions of d-amphetamine on locomotion were obscured by high baseline levels of motor activity induced by the novel environment. Continuous measurements of habituated rats may provide a more sensitive means of evaluating stimulant actions of drugs in screening tests. The observed changes in patterns of onset and offset of increased locomotion and of stereotypy were consistent with the view that these types of behaviour are, to some extent, independently, mediated.

A simple method for modifying a standard activity wheel to increase sensitivity

A simple and highly sensitive method of automating the acquisition of activity wheel data on animals in isolation is described. As well as being inexpensive and quickly constructed the modification is entirely maintenance free.

Techniques used to assess the efficacy of psychotropic drugs: a critical review

Some relevant literature concerning the techniques used to assess psychotropic drug efficacy is evaluated and summarized, and the need for an objective dependent variable to assess behavioral changes associated with drug effects is indicated. The paper concludes that the most obvious basic requirements for the evaluation of psychotropic drugs at the human level are the development and maintenance of stable and reproducible baselines against which to assess drug-correlated changes. As of this date, such a measure has not been developed.

Experimental effects of amphetamine: supplementary report

As a supplement to a previous review, generalizations related to the experimental effects of amphetamine on food-motivated operant behavior, bodily activity and avoidance conditioning are evaluated in terms of recent evidence. Acceptance of generalizations related to the drug's action on such behaviors requires that one also accept numerous qualifications or limitations in terms of drug-dose factors, S variables, and task characteristics. However, the desirability of such generalizations is stressed.