Effects of olanzapine on anxiety-related behaviour in male and female rats assessed after 21-24 and 42-45 days of chronic treatment.

Olanzapine can decrease anxiety and impair memory, but there is limited information about length of treatment or sex differences in its effectiveness. Therefore, effects of 21-24 and 41-45 days of treatment and sex differences on anxiety-related behaviour and spatial memory were assessed in PVG/c (PVG/c is the internationally recognised way of referring to this rat strain) male and female rats. From 70 days after birth (PND70), all rats received no drug or 6, 11 or 15 mg/kg/day olanzapine via drinking water. From PND91, they were given four daily tests in an open field, light-dark box, zero maze and Y maze, and then again 21 days later from PND112. At PND91-94, all olanzapine doses decreased open-field ambulation and walking, and 6 and 15 mg/kg/day decreased rearing, increased immobility while 15 mg/kg/day decreased shuttles in the light/dark box (all suggesting higher anxiety). At PND112-115, 11 mg/kg/day increased open-field ambulation, walking, rearing, centre occupancy and light/dark-box shuttles and light-side entries while decreasing open-field immobility and corner occupancy (all suggesting lower anxiety). There were also several results in the open field and light/dark box suggesting olanzapine decreased anxiety for males but increased it for females. A significant olanzapine-related preference for the novel Y-maze arm either improved spatial memory, or decreased anxiety. Olanzapine thus appeared anxiogenic after 21 days' treatment, becoming anxiolytic after 42 days. This could depend on the sex of the rats (females more responsive to lower doses), and the dose (11 mg/kg/day being most effective). Therefore, while olanzapine was generally anxiolytic, it also had some treatment length- and sex-related anxiogenic effects.

Sex still matters: has the prevalence of male-only studies of drug effects on rodent behaviour changed during the past decade?

During the past 10 years, for a number of biomedical disciplines, including behavioural pharmacology, there have been appeals to include both sexes in animal studies of processes that are not sex specific. In 2007, a survey of experimental studies of drug or other chemical effects on rodent behaviour, published in five prominent journals over 20 months (February 2005 to September 2006, inclusive), revealed that 85% of these conducted with rats and 78% of these conducted with mice involved males only. This was in spite of the evidence of sex differences in responsiveness to an increasing number of compounds. To see if the situation has improved, the survey was repeated with the same journals for a comparable period namely, February 2016 to September 2017 (inclusive). Even though there have been repeated appeals for biomedical research that is not sex specific to involve both sexes, it was apparent that little has changed since 2005-2006, as 82% of rat and 75% of mouse studies were again conducted with males only. However, there was an increase in studies with mice, which may be owing to a greater interest in genetic factors. The male-only situation could be rectified by appropriate funding agencies and journals that publish behavioural pharmacological research insisting that both sexes must be included in research that is not sex specific along with valid scientific justification for single-sex studies, as now typifies some other disciplines.

Treatment with 1-benzylpiperazine (BZP) during adolescence of male and female hooded rats exposed to environmental enrichment: Subsequent behavioral outcomes.

From 30 days after birth until the completion of the study, male and female rats were caged in same-sexed twos or threes either with (enriched cages, EC) or without several objects for them to explore (standard cages, SC). From 41 to 50 days of age (late adolescence), they received a daily intraperitoneal injection of saline, or 10 or 20 mg/kg of the monoaminergic agonist drug of abuse, 1-benzylpiperazine (BZP). Ten days later (PND60+), their behavior was observed over several days in an open field, an elevated plus maze, a light-dark box and (to assess short-term memory) a Y maze in which one of the arms had been changed in brightness between two trials. These tests were repeated from 40 days after PND60+, namely PND100+. While open-arm occupancy at PND100+ in the plus maze was lower following both doses of the drug for SC rats only, other examples of BZP-related heightened anxiety were confined to EC rats. This suggested that enrichment had enhanced rather than reduced any anxiogenic effects of the drug treatment. There was no plausible evidence of BZP-associated impaired spatial memory required to recognize the changed novel Y-maze arm. Instead, changes in novelty preferences or neophobia-related anxiety were most likely. While there were also some examples of sex and age differences in the later effects of BZP, in most cases these were evident at both ages following treatment with both BZP doses. A number of overall BZP, cage, sex and age differences, independent of enrichment effects, were also observed.

Sex-dependent modification by chronic caffeine of acute methamphetamine effects on anxiety-related behavior in rats.

For fourteen days, male and female PVG/c hooded rats were provided continuously with either pure drinking water, or water containing caffeine in a quantity approximating a daily dose of 31.1 mg/kg. Then at intervals of 3 days, they were administered 1, 2 mg/kg methamphetamine (MA) or saline before being tested for anxiety-related behavior in a zero maze or a light/dark box, or their short-term spatial memory was assessed in a Y maze following introduction of a novel brightness change in one of the arms. Each rat experienced each type of apparatus with the same acute MA or saline treatment while still exposed to chronic caffeine or pure drinking water. While chronic caffeine on its own did not affect any behavioral measure, acute MA was anxiolytic for male rats suggested by increased entries and occupancy of zero-maze enclosed areas, and decreased emergence latencies and increased entries into the light/dark-box light compartment. Females were less affected than males by MA in both types of apparatus unless they also consumed caffeine. For male rats, choices of the Y-maze novel arm were affected by neither caffeine nor MA, but for females provided with unadulterated water, such choices were reduced by 1 mg/kg MA but increased for those exposed to caffeine, thereby suggesting either impaired or improved memory respectively. However, changes in anxiety could also explain these results. Overall, results generated in the three types of apparatus supported potentiation by caffeine of any effects of MA on anxiety for females only.

Effects of acute caffeine on anxiety-related behavior in rats chronically exposed to the drug, with some evidence of possible withdrawal-reversal.

For 20days male and female PVG/c hooded rats were provided with caffeinated (approximately 50mg/kg/day) or unadulterated drinking water, and then their anxiety-related behavior was observed in an open field and elevated plus maze. Their choices of a brightness change were also observed in a Y maze to assess any caffeine effects on spatial memory. 24h later, all rats were tested again following an intraperitoneal injection of 50mg/kg acute caffeine, or vehicle. Earlier chronic caffeine decreased ambulation, walking, rearing, center occupancy and increased immobility in the open field thereby suggesting increased anxiety. However, occupancy of the plus-maze open arms and the Y-maze novel arm were increased by caffeine for male rats, but decreased for females probably because of sex differences in control levels of the response rather than to drug effects on anxiety and memory respectively. Following caffeine withdrawal, acute caffeine had the opposite effect to chronic treatment namely, increased open-field ambulation, walking, center occupancy and decreased immobility and defecation for caffeine-naïve rats that were suggestive of decreased anxiety. Similar but more consistent effects (plus decreased emergence latencies from a darkened start box into the open field) also typified the caffeine-experienced rats which in this case may have been accentuated by caffeine withdrawal-reversal. There was no evidence of either chronic or acute caffeine affecting spatial memory measured in the Y maze. There were also examples of lower overall activity and higher anxiety in male rats, than in females, and some sex-dependent caffeine effects.

Increased anxiety and impaired spatial memory in young adult rats following adolescent exposure to methylone.

This study investigated the possibility that treatment of adolescent rats with the substituted cathinone, 3,4-methylenedioxymethcathinone (methylone), might result in heightened anxiety and/or impaired memory during early adulthood, as has been shown for other designer drugs. For 10 consecutive days from 35days after birth (PND35-44, early adolescence) or 45days after birth (PND45-54, late adolescence), male and female PVG/c rats were administered saline or 8.0mg/kg methylone via intraperitoneal injection. When 90days old (early adulthood), their anxiety-related behavior was recorded in an open field and a light/dark box. Acoustic startle amplitude was also measured as well as their spatial memory which was determined by their ability to detect which arm of a Y maze had changed in brightness between an acquisition and a retention trial. Previously methylone-treated rats showed increased anxiety-related behavior only in the open field as reflected in decreased ambulation, and increased corner occupancy and defecation. In the latter two cases, the increases depended on the age of treatment. Also, for defecation, only male rats were affected. In addition, methylone-treated rats displayed signs of impaired spatial memory, independent of anxiety, through their reduced ability to detect a novel changed Y-maze arm. The results of the study suggested some possible consequences in adulthood of methylone use during adolescence. There were also several examples of female rats exhibiting higher overall frequencies of activity and anxiety-related responding than males that were consistent with them being the more active and less anxious of the two sexes.

Strain-dependent effects of acute caffeine on anxiety-related behavior in PVG/c, Long-Evans and Wistar rats.

To assess the possibility that acute caffeine's behavioral action might depend on rats' strain, effects of 50mg/kg of the drug were observed on activity, anxiety-related behavior and habituation learning in male and female rats from three different strains, namely PVG/c, Long-Evans and Wistar. All subjects were tested in an open field, an elevated plus maze and a light-dark box. For the three strains combined, increased occupancy of the center of the open field and entries of the open plus-maze arms with caffeine suggested caffeine-induced anxiolysis, whereas increased grooming in the open field, decreased rearing in the plus maze and increased risk assessment in the light-dark box were consistent with anxiogenesis. Caffeine also reduced open-field rearing only for PVG/c rats, and entries into and occupation of the light side of the light-dark box only for Long-Evans rats, and increased total defecation in the three types of apparatus for all three strains combined. Overall, caffeine appeared to be mainly anxiogenic. The drug also increased open-field ambulation for PVG/c rats and walking for all rats, but decreased open-field ambulation and entries into the plus maze closed arms for Wistar rats alone. In general, Wistar rats appeared to be the least and Long-Evans the most anxious of the three strains investigated. Caffeine also decreased within-session habituation of open-field ambulation for PVG/c rats alone, thereby suggesting strain-dependent interference with non-associative learning and short-term memory. Several overall sex differences were also observed that supported female rats being more active and less anxious than males.

Drug-, dose- and sex-dependent effects of chronic fluoxetine, reboxetine and venlafaxine on open-field behavior and spatial memory in rats.

In an effort to address the need to include both sexes in studies of effects of the SSRI fluoxetine, the NRI reboxetine and the SNRI venlafaxine on anxiety-related behavior and memory along with the use of chronic drug administration, male and female PVG/c rats were fed diets containing two doses of each drug for 21 days. The rats' anxiety level was then assessed in an open field. Short-term spatial memory for a brightness change in a Y maze was also measured. While there was little evidence of anxiolytic effects of any of the drugs, both fluoxetine and, to a lesser extent, venlafaxine appeared to be mainly anxiogenic in their action depending on both dose and sex. Reboxetine was relatively ineffective in this respect. Ability to locate the Y-maze arm that had changed (from white to black) seemed to be impaired for male (but not female) rats by both fluoxetine and venlafaxine and, to a much lesser extent, by reboxetine. Given the relative ineffectiveness of reboxetine in either test, it is possible that the effects of the other two drugs on both anxiety and memory were mainly due to their serotonin reuptake inhibiting properties. The differences that occurred between males and females in responsiveness to all three drugs supported the long-held view that both sexes should be investigated in studies of this sort, especially in view of reports of sex differences in effects of clinically prescribed antidepressants.

Evidence for anxiolytic effects of acute caffeine on anxiety-related behavior in male and female rats tested with and without bright light.

Male and female PVG/c rats were observed in an open field (OF) and an elevated plus maze (EPM) either with or without a bright light stressor (600-692 lx) following an intraperitoneal injection of saline, 25 or 50mg/kg of caffeine. One week later, the same rats were observed under the same drug and lighting conditions but in the opposite apparatus to that experienced earlier. Either the higher or both doses of caffeine decreased anxiety as indicated by increased OF rearing and decreased grooming, immobility and corner occupancy (in the presence of bright light). A similar interpretation applied to caffeine-related increased entries into and observations in the EPM open arms for males only, and increased entries into the open arms for females alone in the presence of bright light. Bright light increased anxiety as shown by longer latencies of emergence into the OF and decreased ambulation and, for males only, decreased center occupancy and increased corner occupancy. Fewer entries into the open arms in the presence of bright light for females only also suggested heightened anxiety. Apart from one OF and one EPM measure, bright light did not appear to markedly influence the effects of caffeine which were concluded to be primarily anxiolytic, with males being more affected than females. Although the central mechanisms responsible for caffeine's anxiolytic action remain to be established, it is possible that antagonism of A2A adenosine receptors might somehow be involved.

Increased anxiety-related behavior in male and female adult rats following early and late adolescent exposure to 3,4-methylenedioxymethamphetamine (MDMA).

Subsequent behavioral effects in adulthood of daily exposure to MDMA during early or late adolescence were assessed in both male and female rats. From either postnatal day (PND) 35 (early adolescence) or PND45 (late adolescence), PVG/c rats of each sex were exposed via intraperitoneal injections to saline or 10mg/kg MDMA for 10 consecutive days. They were regularly weighed during treatment and again on PND90. At this age, their anxiety-related behavior was determined from frequencies of ambulation, rearing, grooming, defecation and occupancy of the center and corners of an open field, as well as entries into and time spent in the light compartment of a light-dark box. Spatial and working memories were assessed by preferences for a novel Y-maze arm, and by recognition of a novel object. MDMA-exposed rats gained less weight during treatment than saline controls but were heavier on PND90 depending on their sex or age when treated. As shown by decreased open-field ambulation (for males only) and increased defecation plus fewer entries into the light compartment of the light-dark box and entries into both arms of a Y maze, MDMA exposure increased adult anxiety-related behavior particularly for rats treated during late adolescence. There was no evidence of any effects on either spatial or working memory.

Anxiolytic effects of environmental enrichment attenuate sex-related anxiogenic effects of scopolamine in rats.

In groups of four same-sexed animals, PVG/c hooded rats were housed for 4.5 months in standard or enriched cages containing several objects that could be explored and manipulated. On separate occasions, each rat then experienced two consecutive daily trials in an open field, a light-dark box or a Y maze with arm inserts that enabled an acquisition trial comprising one black and one white arm to be changed for a retention trial consisting of two black arms. Before their trials in the open field and light-dark box, and following each acquisition trial in the Y maze, the rats received an intraperitoneal injection of 2 mg/kg scopolamine or isotonic saline. In the open field, enrichment led to higher levels of ambulation, walking, rearing and occupancy of the center of the apparatus and shorter emergence latencies from the dark into the light compartment of the light-dark box accompanied by more entries of this compartment. Enrichment also increased entries of and time spent in the changed (or novel) Y-maze arm only for male rats treated with scopolamine. The drug decreased rearing and increased grooming in the open field as well as increasing emergence latencies and decreasing entries of and the time spent on the light compartment of the light-dark box. The main results were interpreted as enrichment having attenuated anxiogenic effects of the behavioral testing and the action of scopolamine for male (but not female) rats in their choices of the novel arm in the Y maze.

Subsequent anxiety-related behavior in rats exposed to low-dose methadone during gestation, lactation or both periods consecutively.

In order to assess the long-term behavioral consequences of exposing rats to methadone during gestation, lactation or both periods consecutively, pregnant Wistar dams were provided with drinking water containing approximately 2.39 mg/kg/day methadone. Soon after birth, litters of offspring were assigned to methadone-naïve foster mothers. Half of these foster mothers were then provided with drinking water containing methadone (approximately 2.86 mg/kg/day), while the other half received unadulterated water. Maternal weight gain, pregnancy duration, litter sizes, sex ratios and average pup weights were recorded. Following weaning on postnatal day (PND) 28, individual rats were weighed and inspected for physical abnormalities and stress reactions at PND20, 60 and 120. At these same ages, observations were also made of the rats' behavior in an emergence apparatus, and an open field. Apart from a smaller number of full-term pregnancies, there were no effects of any type of methadone treatment on physical measurements recorded at any age. Nor were there any behavioral effects of gestational methadone experienced on its own. However, methadone experienced during lactation (without gestational exposure) decreased emergence speed at PND30, and for all testing ages combined, increased open-field ambulation (males only), walking, rearing and occupancy of the center of the apparatus. Exposure to methadone during both gestation and lactation decreased emergence latencies at PND30 and, for all ages combined, decreased ambulation (males only), center occupancy and defecation. The subsequent behavioral effects of methadone were largely confined to lactational exposure and, when combined with gestational exposure, suggested increased anxiety.

Prolonged treatment with vitamins C and E separately and together decreases anxiety-related open-field behavior and acoustic startle in hooded rats.

Adult male and female hooded rats (about 110 days old) consumed vitamins C and E separately and combined together in their drinking water and were assessed for anxiety approximately 50 and then 80 days later in an open field and an acoustic startle apparatus. They were tested when 160+ days old, and then again at 190+ days. For both testing ages combined, the vitamins and their combination increased open-field ambulation and occupancy of the four center squares of the apparatus, while also accordingly decreasing occupancy of the four corners. Treatment with vitamins C and E separately and combined together also decreased acoustic startle amplitude. While there were several significant overall sex and testing age differences, there was no evidence that the vitamin treatment effects were dependent on the operation of either variable. There was also no evidence of synergism between vitamins C and E in their effects. It was suggested that decreases in anxiety produced by the vitamins may have arisen from their antioxidant properties, attenuation of cortisol activity or some as yet undetermined effects on anxiety-related brain structures and neurotransmitters.

Adult anxiety-related behavior of rats following consumption during late adolescence of alcohol alone and in combination with caffeine.

During late adolescence (postnatal days, PNDs, 45-55), male and female hooded rats were exposed to alcohol (1.14-1.33 g/kg/day), caffeine (27.03-27.22 mg/kg/day) or alcohol and caffeine together (1.20-1.34 g/kg/day alcohol plus 23.85-26.48 mg/kg/day caffeine) via their drinking water. The rats' anxiety-related behavior was then assessed on reaching mid adulthood at PND120 in a light-dark box and an open field. For males only, alcohol alone led to increased entries of the light-dark box and (compared with water- or caffeine-exposed subjects) open-field rearing. Alcohol and caffeine combined also increased entries of the light-dark box light compartment and open-field ambulation for males only. The drug combination led to more male ambulation than for alcohol alone, and higher occupancy of the center squares of the apparatus than for males in any other group. Although alcohol alone had no subsequent effects on female behavior, alcohol and caffeine combined led to fewer entries of and less time spent in the light-dark box side then females in any other group. The drug combination also led to less female ambulation in the open field compared with either water- or caffeine-exposed females. The results were interpreted as sex-related potentiation by caffeine of alcohol's developmental effects that resulted in lower levels of adult anxiety in male, but higher levels in females. The possible significance of this outcome for humans, especially females, was discussed.

Enhanced habituation and decreased anxiety by environmental enrichment and possible attenuation of these effects by chronic alpha-tocopherol (vitamin E) in aging male and female rats.

Middle-aged 330-day-old male and female hooded rats were group-housed for nearly 5 months in either standard cages, or in cages containing objects. Each cage also provided either pure water, or a solution of vitamin E (DL-alpha-tocopherol acetate) for drinking. Records were kept of averages for each cage of the rats' body weights and the volume of fluid/100g average body weight drunk. The average daily dose of tocopherol was approximately 162 and 173mg/kg for males and females respectively. Males (but not females) kept in enriched cages weighed less than those from standard cages. They also drank less fluid than females who also drank more tocopherol solution than males. When 490+days old, for rats provided with water, enrichment led to decreased open-field ambulation and increased within-session decrements in the response (habituation). Enrichment also led to decreased occupancy of the center of the apparatus for males only and, for all rats combined, increased grooming behavior. It was concluded that the effects of enrichment on aged rats were due to increased within-session habituation to novelty and decreased anxiety similar to what has been suggested for younger animals. Tocopherol appeared to interfere with effects of enrichment possibly because of pro-oxidant-related increased anxiety.

A comparison of 1-benzylpiperazine and methamphetamine in their acute effects on anxiety-related behavior of hooded rats.

Following i.p. treatment with saline, 10 or 20 mg/kg 1-benzylpiperazine, or 1 or 2 mg/kg methamphetamine, hooded rats were observed in an open field, a light-dark box and (24 h after exposure to the drugs) a Y maze with one novel and one familiar arm. Both drugs increased open-field rearing and ambulation, but only methamphetamine increased and decreased respectively occupancy of center squares and corners, while stereotyped head movements were increased by 20 mg/kg benzylpiperazine. Time spent in and entries of the light compartment of the light-dark box were decreased by benzylpiperazine but not methamphetamine, and entries of the novel Y-maze arm were decreased by methamphetamine for male rats only. Although most behavior emitted in the open field and light-dark box following treatment with methamphetamine could be ascribed to the drug's locomotor stimulant effect, increased stereotypy with the high dose probably interfered with this action for benzylpiperazine. However, both drugs may have led to some anxiety-related novelty avoidance in the Y maze. Overall, the patterns of results for the two drugs revealed more similarities than differences (with methamphetamine possibly being more effective than benzylpiperazine) and thus supported the view that, because of commonalities in their neurochemical effects, benzylpiperazine may have similar abuse and dependence risks to methamphetamine.

Increased emotional reactivity in rats following exposure to caffeine during adolescence.

From 45 to 55 days after birth, male and female rats were treated via daily intraperitoneal injections with either isotonic saline, or 15 or 30 mg/kg caffeine. When 72-82 and 112-122 days old, their activity and emotional reactivity were assessed by means of frequencies of rearing, ambulation, immobility, defecation and urination recorded in an open field, as well as their occupancy of corners and center squares of the field, and their partial emergence and latencies to fully emerge from a small darkened chamber into a brightly lit arena. Rats treated with caffeine were probably more emotionally reactive than untreated controls as suggested by more immobility and defecation and urination. There were also effects on rearing and ambulation that might have arisen from increased impulsivity. Further evidence of caffeine treatment-induced higher emotional reactivity was found in the heavier adrenal glands of a small number of 10 months-old males. This occurred in the absence of any caffeine treatment effects on spatial reference memory measured by ability to identify a novel Y-maze arm. Changes between the two testing ages in rearing and emergence latencies, and sex-dependent changes in ambulation, defecation and corner and center squares occupancy, along with immobility for 30 mg/kg caffeine-treated subjects, were discussed in the light of possible changes in emotional reactivity. Sex differences in open-field rearing and ambulation, and testing age-dependent sex differences in corner and center squares occupancy were ascribed to higher emotional reactivity in males.

An intra-species demonstration of the independence of distance and time in turn alternation of the terrestrial isopod, Porcellio scaber.

In a study of turn alternation in the terrestrial isopod Porcellio scaber (woodlouse), smaller individuals (<11 mm long) took significantly longer to traverse a 60-mm open-ended post-forced-turn runway following a 90 degrees forced turn, than larger subjects (>11 mm long). However, there were no significant differences between the two groups in their probability of alternating, or in the magnitude of alternating turns as reflected in the size of the free-turn angles they turned on emerging from the runway. Nor was there a significant relationship for either group between the time taken to traverse the runway and either the probability of alternating or the size of a free-turn angle. In a second experiment, significant alternation occurred after woodlice emerged from runways that were 30 and 60 mm long, but not when they were 100 or 145 mm long. Their free-turn angles also became smaller as the runway length increased. Overall, the results of the three experiments supported the long-held view that, for reasons not yet understood, distance and time cannot necessarily be equated in the determination of invertebrate turn alternation.

Sex does matter: comments on the prevalence of male-only investigations of drug effects on rodent behaviour.

Despite abundant evidence of sex differences in the effects of drugs on nonsexual behaviour in rats and mice, most researchers continue to investigate male animals exclusively. This was evident from a survey of all relevant research reports published during the period February 2005-September 2006 (inclusive) in recent issues of five representative behavioural pharmacological journals. Reasons for excluding female animals from most studies are discussed along with attempts to justify the use of either male or female animals only, and the value of including both sexes (especially when a drug effect is poorly understood). Although there are other factors that can influence the effects of drugs, such as strain, age and social density, the sex of experimental animals is the easiest to control and thus is well suited to inclusion in pharmacological investigations. It is accordingly suggested that, as has been recommended many times in the past, animals' sex should play a more important part in future research than is still currently the case.

Rats' responsiveness to tactile changes encountered in the dark, and the role of mystacial vibrissae.

This study aimed to assess male and female rats' ability to utilize egocentric cues for detecting a change in tactile stimulation encountered in the dark (and possible sex differences). It also investigated the role of mystacial vibrissae in tactile discrimination in this particular setting. Hooded rats of both sexes were accordingly exposed, in the dark, to Y-maze arms with either two rough (sandpaper) or two smooth floors (Perspex), or one rough and one smooth floor. One of the floors was then changed to the opposite type of surface and the rats' ability to locate and explore this changed (or novel) arm in the dark was measured. Both sexes were able to complete this task successfully thereby suggesting that they had used egocentric body cues, rather than visual or olfactory cues for locating the position of the novel arm. Because rats with all their mystacial vibrissae removed were not seriously disadvantaged in locating and exploring the tactually novel arm, it appeared that their ability to discriminate between the tactile properties of the maze arms was not crucially reliant on their whiskers and allied trigeminal system, and may have also involved tactile receptors in their paws. It was concluded that rats of both sexes were able to utilize egocentric cues in detecting a tactile change, and did not rely exclusively on mystacial vibrissae for discriminating between the tactile properties of the maze-arm floors.