Eva Macúchová

Do the effects of prenatal exposure and acute treatment of methamphetamine on anxiety vary depending on the animal model used

The aim of the present study was an evaluation of prenatal exposure to acute methamphetamine (MA) treatment on manifestations of anxiety. Anxiety was evaluated in adult animals in three different experimental models: the Elevated plus-maze (EPM), Social interaction test (SIT) and Ultrasound vocalization (USV). Female rats were administered saline (S) or MA (5 mg/kg) daily throughout their entire gestation period. The male progeny, in adulthood, were administered with challenge dose of S or MA (1 mg/kg) prior to evaluation of anxiety. The study demonstrated that prenatal MA exposure increased the anxiogenic effect on evaluated behaviour patterns in the USV model and to a lesser degree in the EPM model. In addition, the acute MA challenge in adulthood decreased the time spent during social interaction suggesting an anxiogenic effect in the SIT model as well. On the other hand, some of the evaluated parameters (e.g. the number of head-dipping in the EPM and number of dropped boluses in the SIT) also suggest MA-induced anxiolytic effects. Sensitization to a MA challenge was apparent in several parameters of the EPM (e.g. increased number of entries to the closed arms, increased stretched attend postures and increased approach-avoid conflicts) and SIT (total social interaction and following). The present data demonstrate that prenatal MA exposure and adult challenge of the same drug have diverse effects on animal behaviour that depends on the type of anxiety model used.

Gender differences in the effect of adult amphetamine on cognitive functions of rats prenatally exposed to methamphetamine.

Psychostimulants have been shown to affect brain regions involved in the process of learning and memory consolidation. It has been shown that females are more sensitive to the effects of drugs than males. The aim of our study was to investigate how prenatal methamphetamine (MA) exposure and application of amphetamine (AMP) in adulthood would affect spatial learning of adult female and male rats. Mothers of the tested offspring were exposed to injections of MA (5mg/kg) or saline (SA) throughout the entire gestation period. Cognitive functions of adult rats were evaluated in the Morris Water Maze (MWM) tests. Adult offspring were injected daily with AMP (5mg/kg) or SA through the period of MWM testing. Our data from the MWM tests demonstrates the following. Prenatal MA exposure did not change the learning ability of adult male and female rats. However, AMP administration to adult animals affected cognitive function in terms of exacerbation of spatial learning (increasing the latency to reach the hidden platform, the distance traveled and the search error) only in female subjects. There were sex differences in the speed of swimming. Prenatal MA exposure and adult AMP treatment increased the speed of swimming in female groups greater than in males. Overall, the male subjects showed a better learning ability than females. Thus, our results indicate that the adult AMP treatment affects the cognitive function and behavior of rats in a sex-specific manner, regardless of prenatal exposure.

Does Prenatal Methamphetamine Exposure Induce Cross-sensitization to Cocaine and Morphine in Adult Male Rats?

The aim of the present study was to examine the cross-sensitization induced by prenatal methamphetamine (MA) exposure to challenge dose of cocaine or morphine. Rat mothers received a daily injection of MA (5 mg/kg) or saline throughout the gestation period. Adult male offspring (prenatally MA- or saline-exposed) were divided to groups with challenge doses of saline (1 ml/kg), cocaine (5 mg/kg) or morphine (5 mg/kg). Behavior in unknown environment was examined in Laboras, nociception in Plantar test, and active drug-seeking behavior in conditioned place preference (CPP). Our data demonstrate that cocaine increased the exploratory activity in Laboras test in prenatally saline-exposed, but decreased it in prenatally MA-exposed rats. An analgesic effect of cocaine was demonstrated only by the tail withdrawal and it was independent of the prenatal drug exposure. CPP test showed that prenatal MA exposure induced rather tolerance than sensitization to cocaine. In contrast to cocaine effects, morphine decreased rearing activity in both, prenatally MA-exposed and saline-exposed rats, and locomotion only in prenatally MA-exposed rats in the Laboras. In the Plantar test, the results demonstrated that morphine had an analgesic effect in prenatally saline-exposed rats but this effect was suppressed in prenatally MA-exposed rats. In the CPP test morphine induced drug-seeking behavior, which however was not affected by prenatal drug exposure. Thus, our data demonstrate that there is a cross-effect between prenatal MA exposure and the challenge dose of other drug in adulthood, however drug-seeking behavior is not increased by prenatal MA exposure as we expected.

How various drugs affect anxiety-related behavior in male and female rats prenatally exposed to methamphetamine

Different forms of anxiety‐related behavior have been reported after a single drug use of many abused substances, however, less is known about how males and females are affected differently from exposure to various drugs. Furthermore, chronic prenatal methamphetamine (MA) exposure was shown to predispose the animal to an increased sensitivity to drugs administrated in adulthood. Using the Elevated plus‐maze test (EPM), the first aim of the present study was to examine how male and female rats are affected by acute drug treatment with subcutaneously (s.c.) administrated (a) MA (1 mg/kg); (b) drugs with a similar mechanism of action to MA: amphetamine (AMP, 1 mg/kg), cocaine (COC, 5 mg/kg), 3,4‐methylenedioxymethamphetamine (MDMA, 5 mg/kg); and (c) drugs with different mechanisms of action: morphine (MOR, 5 mg/kg), and Δ 9‐tetrahydrocannabinol (THC, 2 mg/kg). The second aim was to determine if prenatally MA‐exposed (5 mg/kg) animals show an increased sensitivity to adult drug treatment. The parameters analyzed were divided into two categories: anxiety‐related behavior and anxiety‐unrelated/exploratory behavior. Our results showed in female rats a decreased percentage of the time spent in the closed arms (CA) after MA, and an increased percentage of the time spent in the open arms (OA) after MA, AMP, and COC treatment, indicating an anxiolytic‐like effect. In females, MDMA and THC treatment increased the percentage of the time spent in the CA. An increased percentage of the time spent in the CA was also seen after MOR treatment in females as well as in males, indicating an anxiogenic‐like effect. As far as the interaction between prenatal MA exposure and adult drug treatment is concerned, there was no effect found. In conclusion, it seems that: (a) in some cases female rats are more vulnerable to acute drug treatment, in terms of either anxiogenic‐ or anxiolytic‐like effects; (b) prenatal MA exposure does not sensitize animals to the anxiety‐related effects of any of the drugs.

Effect of Amphetamine on Adult Male and Female Rats Prenatally Exposed to Methamphetamine

The aim of the present study was to examine the cross-sensitization induced by prenatal methamphetamine (MA) exposure to adult amphetamine (AMP) treatment in male and female rats. Rat mothers received a daily injection of MA (5 mg/kg) or saline throughout the gestation period. Adult male and female offspring (prenatally MA- or saline-exposed) were administered with AMP (5 mg/kg) or saline (1 ml/kg) in adulthood. Behaviour in unknown environment was examined in open field test (Laboras), active drug-seeking behaviour in conditioned place preference test (CPP), spatial memory in the Morris water maze (MWM), and levels of corticosterone (CORT) were analyzed by enzyme immunoassay (EIA). Our data demonstrate that in Laboras test, AMP treatment in adulthood increased general locomotion (time and distance travelled) regardless of the prenatal exposure and sex, while AMP increased exploratory activity (rearing) only in prenatally MA-exposed animals. AMP induced sensitization only in male rats, but not in females when tested drug-seeking behaviour in the CPP test. In the spatial memory MWM test, AMP worsened the performance only in females, but not in males. On the other hand, males swam faster after chronic AMP treatment regardless of the prenatal drug exposure. EIA analysis of CORT levels demonstrated higher level in females in all measurement settings. In males, prenatal MA exposure and chronic adult AMP treatment decreased CORT levels. Thus, our data demonstrated that adult AMP treatment affects behaviour of adult rats, their spatial memory and stress response in sex-specific manner. The effect is also influenced by prenatal drug exposure.

Effects of psychostimulants on social interaction in adult male rats.

Psychostimulants are known to have a huge impact on different forms of social behaviour. The aim of the present study was to compare the effects of three different psychostimulants [amphetamine, cocaine and 3,4 methylenedimethoxyamphetamine (MDMA)] on social interaction (SI) in adult male rats. The SI test was performed in a familiar arena and under low-stress environmental conditions. Experimental animals received amphetamine (0.5, 1.0, 1.5 mg/kg), cocaine (0.5, 1.0, 1.5, 2.5, 5.0, 10.0 mg/kg) or MDMA (2.5, 5.0, 10 mg/kg) and control animals received saline (1 ml/kg) 45 min before the SI test. Time spent in SI (individual patterns of social behaviour) and nonsocial activities (locomotion and rearing) were video recorded and then analysed offline, with the following results: (a) all doses of amphetamine decreased SI. Specifically, all doses of amphetamine decreased mutual sniffing, and the higher doses also decreased allo-grooming and following behaviours. (b) The higher doses of cocaine decreased SI, especially mutual sniffing, allo-grooming and climbing over. Cocaine at the dose of 5.0 mg/kg increased genital investigation compared with lower doses. (c) All doses of MDMA decreased mutual sniffing and climbing over; the two higher doses decreased allo-grooming behaviour, and only the highest dose decreased following. The two higher doses of amphetamine and all the doses of MDMA increased locomotion and rearing; cocaine did not affect locomotion, but increased rearing at higher doses. In conclusion, the results confirm the well-known finding that psychostimulants suppress SI, but also show novel differences in the effects of psychostimulants on specific patterns of SI.

The influence of methamphetamine on maternal behavior and development of the pups during the neonatal period

Since it enters breast milk, methamphetamine (MA) abuse during lactation can not only affect the quality of maternal behavior but also postnatal development of pups. The aim of the present study was to examine the effect of injected MA (5 mg/kg) on maternal behavior of rats and the differences in postnatal development, during postnatal days (PD) 1–11, of pups when the pups were directly exposed (i.e., injected) to MA or received MA indirectly via breast milk. Maternal behavior was examined using observation test (PD 1–22) and pup retrieval test (PD 1–12). The following developmental tests were also used: surface righting reflex (PD 1–12), negative geotaxis (PD 9), mid‐air righting reflex (PD 17), and the rotarod and beam‐balance test (PD 23). The weight of the pups was recorded during the entire testing period and the day of eye opening was also recorded. MA‐treated mothers groomed their pups less and returned the pups to the nest slower than control dams. The weight gain of pups indirectly exposed to MA was significantly slower. In addition, pups indirectly exposed to MA were slower on the surface righting reflex (on PD 1 and PD 2) and the negative geotaxis test. In females, indirect exposure to MA led to earlier eye opening compared to controls. At the end of lactation, males who received MA indirectly via breast milk performed worse on the balance beam test compared to males who received MA directly. However, direct exposure to MA improved performance on rotarod relative to controls. Our results suggest that indirect MA exposure, via breast milk, has a greater impact than direct MA exposure.

Sex differences in the strategies of spatial learning in prenatally-exposed rats treated with various drugs in adulthood

HighlightsCocaine, MDMA, THC, and morphine affect the cognitive functions of rats in a sex‐specific manner.Females are more sensitive to the effect of long‐drug treatment than males.Drug‐treated females demonstrate alterations in search strategies in the Morris Water Maze.Alterations in the effect of adult drug treatment are seen with reference to prenatal drug exposure. Abstract In the present study we investigated the sex differences in the effect of adult long‐term drug treatment on cognitive functions of Wistar rats, which were prenatally exposed to MA (5 mg/kg) or saline. Cognitive functions were tested as an ability of spatial learning in the Morris Water Maze (MWM), which consisted of three types of tests: “Place Navigation Test”; “Probe Test”, and “Memory Recall Test”. Adult animals were injected daily, after completion of the last trial, either with saline or cocaine (COC; 5 mg/kg), MDMA (3,4‐methylenedioxy‐methamphetamine; 5 mg/kg), morphine (MOR; 5 mg/kg), or delta‐9‐tetrahydrocannabinol (THC; 2 mg/kg). Results revealed worsened MWM performance in female rats after drug treatment in adulthood. Not only were traditionally investigated parameters affected by drug treatment (latency of platform acquisition, search strategy, distance traveled), but also strategies used by animals (thigmotaxis, scanning). Analyses of search strategies observed in the Place Navigation Test, as well as in the Memory Recall Test, demonstrated variations in the percentage of time spent in thigmotaxis and scanning in females after treatment with COC, MDMA, MOR, and THC. Although we did not see a sensitizing effect of prenatal MA, in some cases the effect of drug treatment in adulthood differed depending on the prenatal drug exposure. The data presented in this study demonstrates that exposure to drugs with various mechanisms of action alters spatial abilities of female rats in the MWM. Alterations in the effect of adult drug treatment with reference to prenatal drug exposure were also found in the present study.

How methamphetamine exposure during different neurodevelopmental stages affects social behavior of adult rats

Social behavior involves complex of different forms of interactions between individuals that is essential for healthy mental and physical development throughout lifespan. Psychostimulants, including methamphetamine (MA), have neurotoxic effect, especially, if they are targeting CNS during its critical periods of development. The present study was aimed on evaluation of changes in social interactions (SI) following scheduled prenatal/neonatal MA treatment in combination with acute application in adulthood. Eight groups of male and eight groups of female rats were tested in adulthood: rats, whose mothers were exposed to MA (5mg/ml/kg) or saline (SA, 1ml/kg) during the first half of gestation (ED 1-11), the second half of gestation (ED 12-22) and neonatal period (PD 1-11). To do this, we compared indirect neonatal applications via the exposed dams with group of rat pups that received MA or SA directly through injections. In adulthood, half animals from each group were injected with MA (1mg/kg), second half with saline 45min prior to the Social Interaction Test. Females and males were observed for social and nonsocial activities of two unfamiliar individuals of the same sex and treatment in a familiar Open field arena. The present study demonstrated that prenatal/neonatal MA exposure leads to decrease the time spent in genital investigation, following and nonsocial activity. Acute dose of MA leads to a decrease in all SI patterns and to an increase in nonsocial activities relative to acute SA. Females were more active than males. Animals exposed to prenatal/neonatal treatment during the second half of gestation (ED 12-22) and throughout lactation period (PD 1-11 indirect/direct) had fewer SI and greater exploratory behavior than animals exposed during the first half of gestation (ED 1-11).