Digiscan Activity Research Articles

Age-series characteristics of locomotor activities in spontaneously hypertensive rats: A comparison with the Wistar–Kyoto strain

This study was to investigate the behavioral specificities of spontaneously hypertensive rats (SHR) and compare them with Wistar–Kyoto (WKY) controls using a 1-year longitudinal study of locomotor activity. Rat locomotor activity was examined every week at 4–12 weeks of age and every month at 4–12 months of age using an Automated Digiscan Activity Monitor system. Six behavioral variables were collected and analyzed: horizontal activity (HA), total distance (TD), movement time (MT), vertical activity (VA), stereotypy count (SC), and margin time (MGT). In general, a significant weekly and monthly age-dependent change ( p < 0.01) in SHR was shown in the HA, TD, VA, SC and MT variables, whereas MGT showed no significant differences ( p > 0.05). However, except for the first observations, SHR was significantly hyperactive relative to WKY for HA, VA, TD, MT and SC ( p < 0.01) before 6 months of age. MGT in SHR were significantly lower than those of WKY ( p < 0.01) before 3 months of age. Only for VA, SHR was more hyperactive than WKY ( p < 0.01) and sustained for 12 months in age. From the present results, by extending the observations of locomotor activity testing from 4 weeks to 12 months of life, we were able to observe an interesting strain difference between SHR and WKY in the development pattern of spontaneous activity levels.

Influence of a natural stressor (predator odor) on locomotor activity in the meadow vole (Microtus pennsylvanicus): modulation by sex, reproductive condition and gonadal hormones.

Sex differences in a variety of non-reproductive behaviors have been indicated to occur in seasonally breeding polygynous promiscuous rodents such as the meadow vole, Microtus pennsylvanicus. The present study was designed to assess the effects of reproductive and hormonal status on the locomotor responses of meadow voles following brief exposure to the odors of a natural predator, the Red fox (Vulpes vulpes). Adult male and female meadow voles, which are seasonal photoperiodically-induced breeders, were housed in either mixed sex pairs under a long, reproductively stimulatory photoperiod (simulating breeding: long light cycle, paired: LLC + P) or in same-sex pairs under a short, reproductively inhibitory photoperiod (simulated non-breeding: short light cycle, non-paired: SLC-NP). On 2 consecutive days following 1 day of baseline activity monitoring, voles were exposed individually for 3 min to fox odor and a novel pungent control odor (extract of almond). The levels of various measures of activity that were displayed by the voles were assessed by an automated Digiscan activity monitoring system. LLC + P (simulated breeding) voles displayed higher basal levels of activity relative to SLC + NP (simulated non-breeding) voles, with males displaying greater activity than females. LLC + P (simulated breeding) males displayed a significant reduction in activity levels following exposure to fox odor relative to control odor. The reductions in activity following fox odor exposure were related to plasma testosterone levels such that a larger behavioral response (i.e. greater reduction) was associated with higher levels of testosterone. Furthermore, dividing males into high and low testosterone groups based on the median levels of testosterone revealed that high but not low testosterone males displayed reductions in activity following exposure to fox odor relative to control odor. No changes in activity levels following exposure to fox odor were noted in SLC-NP males, and either SLC-NP or LLC + P females. These results show that this sexually dimorphic non-reproductive behavior is significantly influenced by reproductive condition and gonadal hormone levels.

Blockade of cannabinoid (CB1) receptors by 141716 selectively antagonizes drug-induced reinstatement of exploratory behaviour in gerbils.

A cannabinoid hypothesis of schizophrenia has been proposed according to which cognitive dysfunction could be associated with dysregulation of an endogenous cannabinoid system. The present study investigated whether SR 141716, a selective CB1 receptor antagonist, was able to reduce the hyperactivity induced in gerbils by various stimulant drugs known to produce or exacerbate schizophrenic symptoms. Cocaine, d-amphetamine, morphine, and Win 55212-2 were administered intraperitoneally (IP) either immediately before placing the animals in the test apparatus (non-habituated gerbils) or after a 2- to 3-h habituation period in the actimeter (habituated gerbils). SR 141716 was given IP 30 min before the injection of stimulant drugs. Horizontal activity was recorded every 10 min for 1 h in Digiscan activity monitor. SR 141716 (0.3-3 mg/kg) dose-dependently suppressed the enhanced locomotor activity induced by each stimulant drug in habituated gerbils, but not in non-habituated animals. Clozapine, an atypical antipsychotic compound, but not haloperidol, shared with SR 141716, the ability to differentially affect drug-induced hyperactivity in habituated versus non-habituated gerbils. The activation of cannabinoid systems is a required, permissive element in the ability of cocaine, d-amphetamine, morphine, and Win 55212-2 to reinstate behaviour, i.e., to override stimulus satiation.

Individual Differences in Radial Maze Performance and Locomotor Activity in the Meadow Vole, Microtus pennsylvanicus

Individual differences in the radial maze performance and locomotor activity of wild-caught and first-generation laboratory-born meadow voles are described. Based on their patterns of response in an eight-arm radial maze the essentially wild voles fell into three behavioral categories: 1) strict algorithmic (i.e., they systematically chose the next adjacent arm to their previous choice); 2) nonalgorithmic (i.e., they ran the maze without any consistent or definable pattern); and 3) nonrunners (i.e., nonperformers of the task who remained relatively immobile in the arms of the maze). The algorithmic and nonalgorithmic voles further differed in their responses to an interference manipulation of the radial maze task. Algorithmic individuals displayed a marked performance deficit, while the nonalgorithmic individuals showed minimal disruption to a 1-min delay interruption of the maze task. Measurements of several aspects of locomotor activity using the automated Digiscan activity monitoring system revealed that the algorithmic individuals also displayed significantly greater levels of activity than the nonalgorithmic or nonrunners, with no significant difference in activity between the latter two groups. These findings suggest that the algorithmic voles were relatively inflexible in their behavior, while the nonalgorithmic individuals were more flexible in their maze performance and likely in their use of spatial and nonspatial information. These individual differences in laboratory measures of learning behavior and locomotor activity in meadow voles are consistent with the polymorphism that is proposed to occur in the wild.

Effect of Olivocochlear Bundle Lesion on Locomotor Activity in Rats

HSIEH, Y.-L., T.-J. CHEN, C.-H. LIN AND S.-S. CHEN. Effect of olivocochlear bundle lesion on locomotor activity in rats. Physiol Behav 64(2) 179–184, 1998. This study was conducted to investigate the effect of olivocochlear bundle (OCB) lesion on spontaneous locomotor activity in Wistar rats. The OCB is an auditory efferent pathway which originates from the superior olivary complex in the brainstem and terminates within the cochlea. It has an inhibitory effect on the auditory end organs. In the present study, the OCB was damaged at the floor of the fourth ventricle using radiofrequency current. The rats’ locomotor activities were then monitored weekly for 2 months using an automated Digiscan activity monitor system. Six behavioral variables were collected and analyzed: horizontal activity (HA), total distance (TD), movement time (MT), vertical activity (VA), stereotypy count (SC), and margin time (MGT). Significant time-dependent increases were noted for HA, TD, VA, and SC following OCB lesion. These results of increasing exploratory and stereotyped behaviors may be caused by the rat experiencing more auditory stimulation than before due to OCB dysfunction and may cause the rat to become more curious to explore its surroundings.

Plasma Testosterone Levels Are Related to Various Aspects of Locomotor Activity in Wild-Caught Male Meadow Voles ( Microtus pennsylvanicus)

PERROT-SINAL, T. S., D. INNES, M. KAVALIERS AND K.-P. OSSENKOPP. Plasma testosterone levels are related to various aspects of locomotor activity in wild-caught male meadow voles (Microtus pennsylvanicus). Physiol Behav 64(1) 31–36, 1998. The relationship between plasma testosterone levels and locomotor activity in wild-caught sexually mature male meadow voles ( Microtus pennsylvanicus) was assessed in the laboratory. Several aspects of locomotor activity were monitored for 1 h on two consecutive days using the automated Digiscan activity monitoring system. Plasma testosterone levels were determined immediately following the second day of activity monitoring. Significant Pearson correlations were obtained between plasma testosterone levels and total distance traveled [ r(10) = 0.55, p < 0.05] and amount of time spent in movement [ r(10) = 0.55, p < 0.05] on the second day. The wild voles showed a reduction in activity levels from the first to the second day of activity monitoring, which is indicative of habituation to a novel environment. This study provides direct evidence for a significant correlation between laboratory measures of behavioral activity and plasma testosterone levels in a wild-caught rodent. These findings indicate that previous assessments of hormone–behavior relationships in laboratory-bred rodents are consistent with the relationship between hormones and behavior in wild rodents.

Cadmium exposure attenuates the initiation of behavioral sensitization to cocaine

Employing a paired-watering procedure to control for differential fluid intake confounds, adult male rats were exposed in the home cage to water containing 100 ppm cadmium chloride, or a control solution containing no added cadmium chloride. On Day 61 of exposure to their respective watering regimens, half the animals from each condition received 12 repeated daily i.p. injections of 10 mg/kg cocaine-HCI, or saline. Locomotor activity (total distance traveled) was recorded in Digiscan Activity Monitors for a 20-min baseline period prior to each injection, and for a 40-min period post-injection. On Day 13 of testing, all animals received saline injections only in the test chambers, in an effort to evaluate the role of conditioned cues in the expression of cocaine sensitization. On Day 14–16 of testing, all animals received successive daily challenges of 10, 20, and 40 mg/kg cocaine in the test chamber. The results indicated that the initiation (development) of behavioral sensitization to 10 mg/kg cocaine was attenuated in cadmium-exposed rats. Moreover, the supersensitivity to higher doses of cocaine during dose-effect testing that was registered by control animals pretreated with cocaine, was not evident in cadmium-exposed pretreatment animals. These data suggests that environmental contaminants may alter drug responsiveness, and thereby may influence patterns of drug selection and use.

Chronic exposure to lead attenuates cocaine-induced behavioral activation

Adult, male rats were exposed to a diet containing 500 ppm (0.05%) lead for 105 days before testing for cocaine-related changes in activity using a Digiscan activity system. Behavioral testing occurred on 6 successive test days. Activity was recorded for 20 min prior to and 40 min after IP injections of either 10, 20, or 40 mg/kg cocaine HCl, with saline injections on the day preceding each drug test day. Cocaine-induced behavioral activation was evident in control diet animals for all three doses (10, 20, and 40 mg/kg). While 10 mg/kg cocaine HCl did not produce behavioral activation in lead-treated animals, both 20 and 40 mg/kg did result in increased activity comparable to that observed in control counterparts.

Sodium arsanilate-induced vestibular dysfunction in meadow voles ( Microtus pennsylvanicus): effects on posture, spontaneous locomotor activity and swimming behavior

Vestibular dysfunction was chemically induced in male meadow voles (Microtus pennsylvanicus) by intratympanic injections (30 mg per side) of sodium arsanilate (atoxyl). The control group received intratympanic injections of isotonic saline. After a one-week recovery period the voles were behaviorally assayed for integrity of their labyrinthine systems. All subjects were tested for the presence of the air-righting reflex and body rotation-induced nystagmus. Three weeks later a multivariate assessment of spontaneous motor activity of the voles was carried out in the automated Digiscan Activity Monitor. In addition, the swimming behavior of the voles was examined. Voles with vestibular dysfunction exhibited pronounced postural abnormalities (head dorsiflexion), were not able to swim with their nose above the water for a 1 min test period, and displayed disorientation and thrashing movements. In the Digiscan activity test the atoxyl-treated voles displayed significantly more activity in the horizontal measures (Ps less than 0.01), including greater distance travelled per movement and greater speed of movements, relative to the control animals. The labyrinthectomized group also spent significantly (P less than 0.05) less time in vertical movements and exhibited significantly more time in stereotypic behavior (P less than 0.01), relative to controls. Atoxyl-treated voles also showed significantly less thigmotaxis (wall-hugging) than the control animals (P less than 0.01). In general, changes in spontaneous behavior observed in the sodium arsanilate-treated voles were consistent with the presence of postural and balance abnormalities and a redirecting of exploratory vertical movements toward horizontal locomotion to the extent that these animals were clearly hyperactive in this dimension. The multivariate behavioral assessment available in the Digiscan Activity Monitoring system, thus seems to be especially useful in the examination of behavioral components affected by vestibular dysfunction.

Effects of cadmium on cocaine-induced changes in activity.

Adult male rats were exposed to a diet that contained 100 parts per million added cadmium or a control diet for 72 days before being tested in a Digiscan activity monitor. During the 1-hr test period, each animal's baseline activity levels were recorded for 20 min. Animals then received intraperitoneal injections of 0, 10, 20, or 40 mg/kg cocaine HCl, and their activity levels were recorded for the remaining 40 min of the test session. The results showed that the 10, 20, and 40 mg/kg doses of cocaine produced behavioral activation in the control-diet animals. For cadmium-treated animals, cocaine-induced behavioral changes at the 10 mg/kg dose were not observed, but increased activity was evident at the two higher doses.

Sodium arsanilate-induced vestibular dysfunction in rats: Effects on open-field behavior and spontaneous activity in the automated digiscan monitoring system

Vestibular dysfunction was chemically induced in Long-Evans rats by intratympanic injections (30 mg per side) of sodium arsanilate (atoxyl). Following a one-week recovery period the rats were behaviorally assayed for integrity of the labyrinthine systems. All subjects were tested for presence of the air-righting reflex, the contact-righting reflex (by lightly holding a sheet of Plexiglas against the soles of the rat's feet), and body rotation-induced nystagmus. All animals were then tested for their ability to remain on a small (15 × 15 cm) platform. Next, the subjects were given two 10-min open-field tests during which ambulation, rearing, grooming, and defecation responses were recorded. Four to five weeks later all rats were tested twice (60 min per session) in the automated Digiscan Activity Monitor which provides a multivariate assessment of spontaneous motor activity. The rats with vestibular dysfunction (Group VNX) took significantly less time to fall off the platform ( p<0.01). They also exhibited significantly more open-field ambulation but fewer rearing responses ( ps<0.01). An examination of group correlation coefficients for open-field variables and the platform test scores revealed some interesting group differences ( ps<0.05). In the Digiscan tests the atoxyl-treated rats exhibited fewer number of horizontal movements, but increased speed for these movements ( ps<0.05). Vertical movements did not differ significantly in incidence, but these movements were greatly reduced in duration ( p<0.001). In general, changes in spontaneous behavior observed in the sodium arsanilate-treated rats were consistent with a loss in ability to balance on the two hind feet (during rearing or grooming) and a redirecting of exploratory vertical movement sequences toward horizontal locomotion, especially in the open-field test. The multivariate behavioral assessment available in the Digiscan Activity Monitoring system seems to be especially useful in the examination of behavioral components affected by vestibular dysfunction.

Behavioral antagonism between lead and cadmium

Adult male rats were exposed to one of four dietary conditions for a period of 60 days. Group Control-Diet received a diet containing no added lead or cadmium, group Lead-Diet received a diet that contained 500 ppm added lead, group Cadmium-Diet received a diet that contained 100 ppm added cadmium, and group Lead-Cadmium-Diet received a diet that contained both 500 ppm added lead and 100 ppm added cadmium. Subsequent to exposure, animals were tested in a Digiscan activity monitor. Animals were then sacrificed and metal concentrations were determined in blood and brain. The results from this experiment showed that lead alone increased movement and vertical activity. Cadmium alone decreased movement and increased rest time. Cotreatment with lead and cadmium failed to produce behavioral differences relative to controls; thus, it seems that the changes in activity caused by one metal are antagonized by the other. Results from the analyses of residues in tissues revealed that blood lead concentrations were lower in the cotreatment condition than the lead along condition. However, brain residue accumulations were not different for these two exposure conditions. There was no evidence that the presence of lead attenuated increases in cadmium residues in blood or brain. Overall, the residue data agree with a central, as contrasted with a peripheral, account of lead/cadmium interaction effects, at least as relates to behavior. Because lead and cadmium were additive with regard to producing decreased body weights, it seems that the toxic effect of these metals is antagonized by cotreatment in some instances, and augmented in others.

The effects of cocaine on multivariate locomotor behavior and defecation

The present study utilized a multifactorial open-field analysis (Digiscan activity) to assess behavioral changes induced by various doses of cocaine known to stimulate locomotion. The measures that were implemented included ambulation, rearing, stereotypic behavior, rotational movements and changes in defecation levels. Thirty-two male Sprague-Dawley rats were habituated to Digiscan-16 Animal Activity Monitors (Omnitech Electronics, Columbus, OH) before being injected with 0.0, 10, 20 or 30 mg/kg cocaine. Rats were kept on a reversed light/dark schedule and tested in the middle of the dark cycle. It was found that cocaine consistently increased activity measures; most prominently affecting the rotational and ambulatory indices. Interestingly, this ‘activity print’ appeared to be dose-dependent and specific to cocaine. Open-field defecation levels were compared to home-cage levels as an additional behavioral correlate. Defecation decreased under all doses of cocaine as compared to control levels (saline injection). This result is attributed to cocaine's weakly sympathomimetic effect.

The quinolinic acid model of Huntington's disease: Locomotor abnormalities

In contrast to other excitotoxins, such as kainic acid, quinolinic acid (QA) may spare a specific population of striatal neurons that is also spared in Huntington's disease (HD). Although several histological and biochemical experiments support the use of QA as a model for HD, to date no behavioral experiments have been performed to examine the suitability of this model. The present study explored the behavioral effects of bilateral intrastriatal microinjections of four doses (75, 150, 225, 300 nmol) of QA in the male rat. Using a multidimensional analysis of spontaneous locomotion (Digiscan activity) and a record of metabolic indicators, such as weight loss, a dose-dependent effect was found. The 75-nmol dose had no significant effect on locomotion or feeding behavior. In contrast, the 150- and 225-nmol doses induced hyperactivity and weight loss, whereas the 300-nmol dose was lethal. The results obtained suggest that striatal injections of 150–225 nmol of QA induce behavioral deficits qualitatively similar though quantitatively less than those which are seen after similar injection of 3 nmol of kainic acid and which have been reported to be comparable to the symptomatology of HD. Together with QA's possible greater histological selectivity, the present results support the use of QA-induced striatal lesions as a behavioral model of Huntington's disease.

Ro15-4513 enhances and attenuates motor stimulant effects of ethanol in rats

The actions of the imidazobenzodiazepine, Ro15-4513 (2.5 mg/kg IP), ethanol (0.50 g/kg, 0.75 g/kg, 1.25 g/kg), and Ro15-4513 in combination with ethanol were assessed using low activity male Charles River (CD) rats. Horizontal (ambulatory) and nonhorizontal (rearing, grooming, etc.) activity were measured in the open field with a Digiscan activity system. When Ro15-4513 was given alone, animals responded in a manner similar to that of the control animals. Ethanol alone, however, resulted in a significant enhancement of activity, with the effect being most pronounced at 0.50 g/kg for horizontal activity and 1.25 g/kg for nonhorizontal activity. A potentiation of the ethanol-induced stimulant effect was observed following pretreatment with Ro15-4513 on the horizontal activity measure for the 1.25 g/kg ethanol group. An attenuation of activity was observed for this group on the nonhorizontal activity measure. Ro15-4513, however, did not affect the stimulation produced by the other doses of ethanol on the nonhorizontal measure. The results suggest that possibility of distinct neurochemical mechanisms in the mediation of horizontal and nonhorizontal activity and that, perhaps, GABA-benzodiazepine mechanisms may play different roles in mediating their ETOH-induced stimulant effect.

“In vivo” studies on the interactions between excitotoxins and gangliosides

In contrast to other excitotoxins, such as kainic acid, quinolinic acid (QA) may spare a specific population of striatal neurons that is also spared in Huntington's disease (HD). Although several histological and biochemical experiments support the use of QA as a model for HD, to date no behavioral experiments have been performed to examine the suitability of this model. The present study explored the behavioral effects of bilateral intrastriatal microinjections of four doses (75, 150, 225, 300 nmol) of QA in the male rat. Using a multidimensional analysis of spontaneous locomotion (Digiscan activity) and a record of metabolic indicators, such as weight loss, a dose-dependent effect was found. The 75-nmol dose had no significant effect on locomotion or feeding behavior. In contrast, the 150- and 225-nmol doses induced hyperactivity and weight loss, whereas the 300-nmol dose was lethal. The results obtained suggest that striatal injections of 150–225 nmol of QA induce behavioral deficits qualitatively similar though quantitatively less than those which are seen after similar injection of 3 nmol of kainic acid and which have been reported to be comparable to the symptomatology of HD. Together with QA's possible greater histological selectivity, the present results support the use of QA-induced striatal lesions as a behavioral model of Huntington's disease.

The catalepsy test: its ups and downs.

The typical catalepsy test consists of placing an animal into an unusual posture and recording the time taken to correct this posture. This time is regarded as an index of the intensity of catalepsy. Catalepsy is a robust behavior, and the lack of standardization does not usually hinder its actual detection. However, the intensity of the cataleptic effect is influenced by minor methodological differences, and thus interpretation and comparison of results across laboratories are difficult. The behavioral catalepsy test can use any of several different apparatus, including wire grids, parallel bars, platforms, or pegs, to situate the animals in unusual positions. The most common, however, is the "bar test," and despite its wide use in psychopharmacological research, even parameters of this test are not standardized. The present article reviews the wide variety of parameters chosen by investigators that measure catalepsy. The methodological issues of repeated testing, scaling of scores, apparatus, animal weight, maximal test duration, behavioral criteria, and other influences are discussed. In addition, a brief review of the neuropharmacological basis of catalepsy is also included. Finally, it is argued that a universal, standardized bar test be adopted by researchers. New data on a novel automated bar test in the Digiscan Activity Monitoring System is presented.

Digiscan activity: automated measurement of thigmotactic and stereotypic behavior in rats.

Visual measures of stereotypy, margin time (thigmotaxis or wall-hugging), and center time were correlated with automated measures using a revised 16 beam version of the Digiscan Animal Activity Monitor System. Rats were injected with d-amphetamine (1.25, 2.5, 5.0 and 10.0 mg/kg), scopolamine (1.25 and 2.5 mg/kg) or saline and drugs were found to increase center time and decrease margin time in a dose-dependent manner, with the maximum effect occurring with 1.25 and 2.5 mg/kg, respectively. At higher doses, an opposite effect was observed. Extremely high correlations between visual and automated recordings of both margin time and center time were found. Since thigmotaxic or wall-hugging behavior has been used as an indicator of emotionality in rats, the results of the present study suggest that these two locomotor variables may be useful additions to the Digiscan multivariate analysis of locomotor behavior. It was also found that a redefinition of stereotypic behavior improved its correlation with visual measurements compared to earlier studies.