Does prenatal methamphetamine exposure affect the drug-seeking behavior of adult male rats?

Behavioural Brain Research 224 (2011) 80–86

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Does prenatal methamphetamine exposure affect the drug-seeking behavior of adult male rats? ∗ ˇ Romana Slamberová , Barbora Schutová, Lenka Hrubá, Marie Pometlová Charles University in Prague, Third Faculty of Medicine, Department of Normal, Pathological and Clinical Physiology, Ke Karlovu 4, 120 00 Praha 2, Prague, Czech Republic

a r t i c l e

i n f o

Article history: Received 17 March 2011 Received in revised form 19 May 2011 Accepted 22 May 2011 Keywords: Methamphetamine Cocaine Amphetamine Conditioned place preference Drug-seeking behavior Prenatal drug exposure

a b s t r a c t Methamphetamine (MA) is one of the most frequently used illicit drugs worldwide and also one of the most common drugs abused by pregnant women. Repeated administration of psychostimulants induces behavioral sensitization in response to treatment of the same or related drugs in rodents. The effect of prenatal MA exposure on sensitivity to drugs in adulthood is not yet fully determined. Because our most recent studies demonstrated that prenatal MA (5 mg/kg) exposure makes adult rats more sensitive to acute injection of the same drug, we were interested whether the increased sensitivity corresponds with the increased drug-seeking behavior. The aim of the present study was to examine the effect of prenatal MA exposure on drug-seeking behavior of adult male rats tested in the conditioned place preference (CPP). The following psychostimulant drugs were used as a challenge in adulthood: MA (5 mg/kg), amphetamine (5 mg/kg) and cocaine (10 mg/kg). All psychostimulant drugs induced increased drug-seeking behavior in adult male rats. However, while MA and amphetamine-induced increase in drug-seeking behavior did not differ based on the prenatal drug exposure, prenatally MA-exposed rats displayed tolerance effect to cocaine in adulthood. In addition, prenatally MA-exposed rats had decreased weight gain after administration of MA or amphetamine, while the weight of prenatally MA-exposed rats stayed unchanged after cocaine administration. Defecation was increased by all the drugs (MA, amphetamine and cocaine), while only amphetamine increased the tail temperature. In conclusion, our results did not confirm our hypothesis that prenatal MA exposure increases drug-seeking behavior in adulthood in the CPP test. © 2011 Elsevier B.V. All rights reserved.

1. Introduction Cocaine, amphetamine and methamphetamine (MA), are psychostimulant drugs that are often abused worldwide. In addition, MA is one of the most common “hard” drug abused by pregnant women [33] that metabolizes slowly and its high is long-lasting (8–24 h) [33]. Therefore, the effect of maternal administration during gestation and its long-term effect on the progeny of the drug-abusing mothers are studied in our laboratory. Our previous works demonstrated impairing effects of prenatal MA exposure on postnatal sensorimotor development, exploratory behavior in adulthood, cognitive functions, nociception and seizure sensitivity [45,46,50–52,62]. Studies of others demonstrated that repeated administration of psychostimulants enhances locomotor activity in response to treatment of the same or related drugs tested in the open field in rodents [48]. This phenomenon is defined as behavioral sensitization or reverse tolerance. Once behavioral sensitization is established, it persists for several months [10]. In addition, there

∗ Corresponding author. Tel.: +420 224902713; fax: +420 224902750. ˇ E-mail address: [email protected] (R. Slamberová). 0166-4328/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.bbr.2011.05.021

are studies showing that abuse of one drug may increase sensitivity to abuse of another drug. This effect is called cross-sensitization [3,4,13,19,28,29,58]. Cross-sensitization between amphetamine and cocaine was first demonstrated with locomotor activity [5,44]. Systematic pretreatment with amphetamine was shown to enhance the acquisition [22] and escalation of cocaine selfadministration [14]. Valvassori et al. [58] found that rats chronically treated with methylphenidate in the adolescent period showed augmented locomotor sensitization to d-amphetamine. In addition, microinjections of amphetamine into the ventral tegmental area have been shown to increase cocaine self-administration under a progressive ratio procedure and to enhance reinstatement of cocaine-seeking [47]. Except for the sensitizing effect of the intermittent administration of psychostimulants in adulthood, there are studies showing that similar effects resulting in increased behavioral sensitivity may be induced by prenatal exposure to psychostimulants and that such effects may be long-term and last up to adulthood [30]. Our most recent studies demonstrated that prenatal MA exposure (5 mg/kg daily) increased the sensitivity to lower dose (1 mg/kg) of the same drug when tested in the open field, pain or seizure models and that this increase corresponds with the increased level of dopamine and its metabolites [6,45,46,53,54,62]. Increased

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predisposition to drug abuse in adulthood has been shown in prenatally cocaine-exposed [12,20,38], cannabinoid-exposed [59] and morphine-exposed offspring [16] relative to controls. They showed increased drug-seeking behavior in both “self-administration test” and “condition place preference test” (CPP). CPP is one of the most widespread drug reward tests because of its relative accessibility and easy use (for review see [57]). Based on Pavlovian conditioning principles, CPP reflects a preference for a context due to the contiguous association between the context and a drug-associated stimulus. It also presents important advantages, among which the possibility to reveal both reward and aversion, to test animals in a drug-free state and to allow simultaneous determination of locomotor activity [13]. The aforementioned studies suggest that prenatal drug exposure may induce “cross-sensitization” independently of the drugs that were the animals exposed to prenatally and in adulthood. Thus, it seems that prenatal drug exposure induces general predisposition to drug addiction in adulthood. To validate the hypothesis, that prenatal drug exposure is able to induce cross-sensitization, the present study investigates the effect of prenatal MA exposure on drug-seeking behavior tested in the CPP test. Three different psychostimulant drugs were used to induce conditioning in adulthood: MA (the same drug and dose as in prenatal period), amphetamine (5 mg/kg) and cocaine (10 mg/kg). 2. Methods 2.1. Prenatal and postnatal animal care Adult female Wistar rats (250–300 g) were delivered by Anlab (Prague, the Czech Republic) from Charles River Laboratories International, Inc. Animals were housed 4–5 per cage and left undisturbed for a week in a temperature-controlled (22–24 ◦ C) colony room with free access to food and water on a 12 h (light):12 h (dark) cycle with lights on at 06:00 h. One week after arrival females were smeared by vaginal lavage to determine the phase of the estrous cycle. The smear was examined by light microscopy. To ensure successful insemination, at the onset of estrous phase of the estrous cycle [56] female rats were housed with sexually mature males overnight. There were always, one female and one male in a cage. The next morning females were smeared for the presence of sperm and returned to their previous home cages. This was counted as gestational day (GD) 1. In total 24 dams were randomly assigned to a MA-treated, a saline-treated, or a control group. On GD 1 the daily injections started and continued to the day of delivery, which usually occurred on GD 22 (for details see [49]). d-methamphetamine HCl (Sigma–Aldrich) was injected subcutaneously (s.c.) in a dose of 5 mg/kg, saline was injected s.c. at the same time in the same volume as MA, and control females were not exposed to any injections. All dams were weighed daily throughout the entire gestation period, but the data showed no differences between treatment groups in weight gain during gestation period. The day of the delivery was counted as postnatal day (PD) 0. On PD 1, pups were weighed, tattooed for further identification and cross-fostered so that each mother received the same number of pups from each of the three treatments (for detailed information see [51]). Each of the 24 mothers raised 12 pups – two of each sex from each prenatal group (control, saline and MA). On PD 21, pups were weaned and group-housed by sex. Animals were left undisturbed until adulthood. In total 72 male rats were used in the present study (24 males per experiment). Always one male rat per group (control, saline- or MA-exposed) was used from each litter to avoid litter effects. Females were used in other experiments that will be part of another study.

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rats (n = 8). Thus, the total number of animals tested in the three experiments was 72. 2.3. Conditioned place preference (CPP) The CPP apparatus dimensions and general procedures were modified according to the work of Sanchez et al. [41]. The apparatus is made of plexiglass, with two main compartments measuring 25 cm × 25 cm × 25 cm (l × w × h) and one central (neutral) compartment measuring 15 cm × 25 cm × 25 cm. Central and main chambers were divided by removable doors. Walls of one of the main compartments were painted with 2.5-cm-wide alternating black and white horizontal lines, walls of the other main compartment were painted with 2.5-cm-wide alternating black and white vertical lines. The neutral compartment was made of gray opaque Plexiglas. The floor of both main compartments was made from wire mesh with different size of the meshes, while the central compartment had smooth plexiglass floor. The place conditioning procedure consisted of three phases: pre-exposure, conditioning, and the CPP test as in work of Mueller and Stewart [35] (see Fig. 1). Pre-exposure: On the Day 1, animals received a single pre-exposure test in which they were placed in the center choice chamber with the doors open to allow access to the entire apparatus for 15 min. The amount of entries and the total time spent in each chamber was monitored and used to assess unconditioned preferences. Conditioning: During the following conditioning phase (8 days), rats were assigned to receive drug pairings with one of the two chambers in a counterbalanced fashion (the ‘unbiased’ procedure). Half of each group started the experiment on the drugpaired side and half on the saline-paired side. On alternate days, rats received s.c. saline (1.0 ml/kg) or drug injections prior to being placed in the other chamber. After administration of drug or saline, animals were allowed to explore the specific chamber for 1 h. Half of each treatment group received s.c. drug injections on the 2nd, 4th, 6th and 8th days; the remaining subjects on the 3rd, 5th, 7th and 9th days. The center chamber was never used during conditioning and was blocked by the doors. CPP test: Two days after the last conditioning trial (Day 12), a test for CPP was given. Animals were placed in the center choice chamber with the doors opened and allowed free access to the entire apparatus for 15 min. The time spent in each chamber and the number of entries was recorded to assess individual preferences. No injections were given during the CPP test, maintaining the same procedure as that used during the pre-exposure test. 2.4. Measurements provided during the experiments Animals were weighed daily and the weight gain was compared between groups. Tail temperature was measured by laser thermometer after each session of the conditioning phase when drug was or was not given and the effect of prenatal exposure and drug in adulthood was statistically analyzed. In addition, tail temperature was measured also after the pre-exposure and CPP sessions. Number of boluses dropped was counted each day during the days of conditioning (with or without drug) and also during the phase of pre-exposure and CPP test. 2.5. Statistical analyses As there were no differences between the animals of the same prenatal exposure that were raised by mothers of different drug treatment, the raising mother (biological vs foster) was not taken as a factor for statistical analyses. Therefore, a Two-Way ANOVA (factors: prenatal exposure, chamber with or without drug) with Repeated Measure (time: before vs after conditioning) was used to analyze differences in the number of entries to chambers and the total time spent in the specific chamber. One-Way ANOVA (factor: prenatal exposure) with Repeated Measure (time: before vs after conditioning) was used to analyze weight gain during the experiment. Two-Way ANOVA (factors: prenatal exposure, days with or without drugs) was used to compare averages of tail temperature and averages of boluses dropped in the days with or without drug administration. One-Way ANOVA (factor: prenatal exposure) was used to see differences in the tail temperature and boluses dropped during the CPP testing on experimental day 12. Fisher LSD test was used for posthoc comparison. Differences were considered significant if p < 0.05 in all statistical analyses.

2.2. Dosages of psychostimulants Adult animals (PD 70–90) were used to test drug reward conditioning and how it is affected by prenatal drug exposure. Three experiments were conducted, each of which used a different drug for conditioning: (1) MA 5 mg/kg; (2) amphetamine 5 mg/kg; and (3) cocaine 10 mg/kg. All drugs were administered s.c. The dose of MA was the same as used prenatally, because lower dose was not sufficient in inducing conditioning (data not shown). The dose of amphetamine (5 mg/kg) was chosen based on the work of Timár et al. [55] showing that such a dose allowed to develop the positive place preference conditioning. While the dose of cocaine that was used in the study of Heyser et al. [21] was not sufficient to induce drug-seeking behavior in our experiment (data not shown), we used the dose of 10 mg/kg of cocaine in the present study similarly to the study of Carey and Gui [9]. There were always three groups based on the prenatal exposure used in each experiment: control without prenatal administration, prenatally saline-exposed rats and prenatally MA-exposed

3. Results 3.1. Methamphetamine (5 mg/kg) There was an increase in the number of entries to the chamber associated with the drug after conditioning [F(1, 42) = 7.4; p < 0.05], but this effect was not affected by prenatal drug exposure [F(2, 42) = 0.05; p = 0.95] (Fig. 2A). Also, there was an increase in the time spent in the chamber associated with drug after conditioning [F(1, 42) = 6.0; p < 0.05], but this increase was not influenced by prenatal drug exposure [F(2, 42) = 0.06; p = 0.94] (Fig. 2B).

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Table 1 The effect of prenatal MA exposure and MA conditioning in the CPP test. Prenatal exposure

Control Saline MA

Weight

Tail temperature

Before conditioning

After conditioning

374 ± 8 387 ± 8 352 ± 8* , #

466 ± 7## 475 ± 7## 444 ± 7* , # , ##

Boluses

Conditioning

CPP test

Days w/o MA

Days with MA

28.99 ± 0.16 28.48 ± 0.16 28.80 ± 0.16

28.48 ± 0.42 29.54 ± 0.42 28.78 ± 0.42

Conditioning

29.43 ± 0.96 29.29 ± 0.82 29 61 ± 0.88

CPP test

Days w/o MA

Days with MA

7.0 ± 0.5 1.4 ± 0.6* 1.3 ± 0.5*

6.9 ± 0.7 7.1 ± 0.7‡ 5.1 ± 0.6†

2.6 ± 0.8 2.4 ± 0.9 1.1 ± 0.7

Values are means ± SEM. Data of tail temperature and boluses during conditioning are presented as averages of all 4 days with or without drug administration. * p < 0.05 vs control animals. # p < 0.05 vs prenatally saline-exposed animals. ## p < 0.0001 vs weight before conditioning. † p < 0.01. ‡ p < 0.001 vs days without MA.

As shown in Table 1, animals gained weight during the experiment [F(1, 21) = 1278.9; p < 0.0001], but the weight of prenatally MA-exposed animals before and after conditioning was lower than the weight of controls or animals prenatally exposed to saline [F(2, 21) = 7.35; p < 0.01]. Table 1 further shows no differences in tail temperature between groups in response to prenatal MA exposure or MA administration during conditioning [F(2, 42) = 2.54; p = 0.09] or CPP test [F(2, 21) = 0.03; p = 0.97]. If boluses are taken into consideration, the data show that MA during conditioning increased the defecation only in animals prenatally exposed to MA or saline, but not in control animals [F(2, 42) = 12.08; p < 0.0001]. There were no differences in the number of boluses dropped during the CPP test when no MA was administered [F(2, 21) = 0.81; p = 0.46] (Table 1). 3.2. Amphetamine (5 mg/kg) There was an increase in the number of entries to the chamber associated with drug after conditioning [F(1, 42) = 6.50; p < 0.05],

but this effect was not affected by prenatal drug exposure [F(2, 42) = 2.08; p = 0.14] (Fig. 3A). For the time spent in the specific chamber, there was an increase in the chamber associated with drug after conditioning [F(1, 42) = 8.80; p = <0.01], but this increase was not influenced by prenatal drug exposure [F(2, 42) = 2.08; p = 0.14] (Fig. 3B). As shown in Table 2, prenatally MA-exposed animals were lighter than controls or prenatally saline-exposed animals [F(2, 21) = 6.84; p < 0.01]. While the animals gained some weight during the experiment [F(2, 21) = 19.15; p < 0.001], the weight gain did not differ based on the prenatal exposure [F(2, 21) = 1.03; p = 0.37]. Table 2 further shows increased tail temperature on the days when amphetamine was administered [F(1, 42) = 10.08; p < 0.01], this tail temperature was not however affected by prenatal exposure [F(2, 42) = 1.02; p = 0.34]. In addition, there were no tail temperature differences between prenatal groups in the day of CPP test [F(2, 21) = 0.27; p = 0.76]. The defecation increased on the days when amphetamine was administered [F(1, 42) = 44.15; p < 0.0001], but

Time-line: Preexposure Day

1

Conditioning (drug injection) 2

3

4

5

6

7

Break 8

9

10

11

CPP test 12

Fig. 1. Time-line of the methodological procedure.

Fig. 2. The effect of prenatal MA exposure and MA conditioning in the CPP test. (A) Number of entries to chambers during the CPP test; and (B) time spent in chambers during the CPP test. Values are means ± SEM. *p < 0.05 main effect of chamber; chamber with MA > chamber without MA.

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Table 2 The effect of prenatal MA exposure and amphetamine conditioning in the CPP test. Prenatal exposure

Weight Before conditioning

Control Saline MA

411 ± 14 407 ± 12 360 ± 9* , #

Tail temperature After conditioning

440 ± 10## 438 ± 10## 407 ± 7* , # , ##

Boluses

Conditioning

CPP test

Days w/o amphetamine

Days with amphetamine

28.95 ± 0.36 29.13 ± 0.40 28.76 ± 0.28

30.20 ± 0.34† 30.16 ± 0.42† 30.09 ± 0.38†

29.38 ± 0.26 29.60 ± 0.22 29 59 ± 0.24

Conditioning

CPP test

Days w/o amphetamine

Days with amphetamine

1.8 ± 0.5 1.4 ± 0.6 1.9 ± 0.5

5.1 ± 0.6‡ 4.9 ± 0.5‡ 5.1 ± 0.6‡

1.0 ± 0.6 0.8 ± 0.5 0.6 ± 0.5

Values are means ± SEM. Data of tail temperature and boluses during conditioning are presented as averages of all 4 days with or without drug administration. * p < 0.01 vs control animals. # p < 0.05 vs prenatally saline-exposed animals. ## p < 0.001 vs weight before conditioning. † p < 0.01. ‡ p < 0.0001 vs days without amphetamine.

this increase was not affected by prenatal exposure [F(2, 42) = 0.05; p = 0.95]. In addition, number of dropped boluses during the CPP test was not altered by prenatal exposure either [F(2, 21) = 0.13; p = 0.88] (Table 2).

p = 0.86]. If boluses are taken into consideration, the data show that cocaine during conditioning increased defecation in all animals regardless of prenatal exposure [F(1, 42) = 15.84; p < 0.001]. There were no differences in the number of boluses dropped during the CPP test when no cocaine was administered [F(2, 21) = 0.14; p = 0.87] (Table 3).

3.3. Cocaine (10 mg/kg) There was an increase in entries into both chambers (with or without drug) in animals prenatally exposed to MA relative to controls or prenatally saline-exposed rats [F(2, 42) = 5.92; p < 0.01], however, there was not an increase in the number of entries after cocaine conditioning [F(1, 42) = 1.55; p = 0.22] (Fig. 4A). In addition, while prenatally saline-exposed and control rats spent more time in the chamber associated with cocaine after conditioning, cocaine conditioning did not induce drug-seeking behavior in prenatally MA-exposed animals [F(2, 42) = 5.76; p < 0.05] (Fig. 4B). As shown in Table 3, prenatally MA-exposed animals were lighter than controls or saline-exposed animals [F(2, 21) = 7.81; p < 0.05]. In addition, while control and prenatally saline-exposed rats gained weight during the experiment [F(2, 21) = 8.04; p < 0.01], the weight of prenatally MA-exposed rats did not change significantly. Table 3 further shows no differences induced by cocaine administration or prenatal exposure in tail temperature during conditioning [F(2, 42) = 0.62; p = 0.54] or CPP test [F(2, 21) = 0.16;

4. Discussion The present data show no increase in the number of visits and in time spent in the chamber associated with drug that would be induced by prenatal MA exposure after conditioning to any of the psychostimulant drugs (MA, amphetamine and cocaine). Despite this fact, the method used in the present study seems to work properly, because animals after conditioning tend to prefer the chamber that was associated with drug administration, while there were no chamber preferences in the pre-exposure phase. Thus, the present study did not confirm our expectation, that prenatal MA exposure will induce increased drug-seeking behavior in male rats in adulthood. This is in disagreement with studies showing increased predisposition of drug abuse in prenatally cocaine-exposed adult rats [12,20,38]. They showed increased drug-seeking behavior in both “self-administration test” and “condition place preference test” (CPP). However note, that none of these studies examined

Fig. 3. The effect of prenatal MA exposure and amphetamine conditioning in the CPP test. (A) Number of entries to chambers during the CPP test; and (B) time spent in chambers during the CPP test. Values are means ± SEM. *p < 0.05; **p < 0.01 main effect of chamber; chamber with amphetamine > chamber without amphetamine. AM: amphetamine.

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Table 3 The effect of prenatal MA exposure and cocaine conditioning in the CPP test. Prenatal exposure

Control Saline MA

Weight

Tail temperature

Before conditioning

After conditioning

406 ± 10 408 ± 11 367 ± 10* , #

434 ± 7## 443 ± 8## 387 ± 8* , #

Boluses

Conditioning

CPP test

Days w/o cocaine

Days with cocaine

29.18 ± 0.36 29.43 ± 0.40 28.52 ± 0.28

29.02 ± 0.34 29.06 ± 0.42 28.90 ± 0.38

29.08 ± 0.36 28.93 ± 0.42 28.68 ± 0.34

Conditioning

CPP test

Days w/o cocaine

Days with cocaine

1.6 ± 0.5 2.5 ± 0.4 2.9 ± 0.5

4.5 ± 0.4† 3.7 ± 0.3† 5.3 ± 0.4†

0.5 ± 0.5 0.6 ± 0.4 0.9 ± 0.5

Values are means ± SEM. Data of tail temperature and boluses during conditioning are presented as averages of all 4 days with or without drug administration. * p < 0.05 vs control animals. # p < 0.05 vs prenatally saline-exposed animals. ## p < 0.0001 vs weight before conditioning. † p < 0.001 vs days without cocaine.

drug-seeking behavior in prenatally MA exposed rats, but used model of prenatal cocaine exposure with conditioning to cocaine or morphine in adulthood. These inconsistencies suggest that cocaine is more potent drug for causing long-term addiction than MA. The only difference in drug-seeking behavior between prenatally exposed groups was present in cocaine conditioning. Specifically, while control and prenatally saline-exposed animals did prefer the chamber associated with cocaine after conditioning period, there was no chamber preference in prenatally MA-exposed animals not only in pre-exposure session, but also in the CPP test. In other words, cocaine conditioning did not increase drug-seeking behavior in prenatally MA-exposed rats, while it induced it in controls and prenatally saline-exposed rats. This suggests that prenatal MA exposure rather decreased than increased drug-seeking behavior relative to control animals. Because prenatal MA exposure did not induce any differences in the preference of MA or amphetamine, but did induce difference in the preference of cocaine, it is possible that the mechanism of action of all psychostimulant drugs may play a role in this effect. Even though all the drugs (MA, amphetamine and cocaine) are known to affect noradrenergic, dopaminergic and serotoninergic systems, the ratio of involvement of these neurotrasmitter systems do differ between these psychostimulant drugs. While MA and amphetamine seem to affect most the noradrenergic, then the dopaminergic and at minimum the serotoninergic system, cocaine seems to affect serotoninergic system the most

[15,39,43]. It should be remarked that even though noradrenalin is released by amphetamine more from noradrenergic nerve terminals than dopamine from dopaminergic nerve terminals, the impact of the psychostimulant drugs on function is more accurately reflected based on the amount of the noradrenergic and dopaminergic innervations or relative abundance of the two neurotransmitters. Since dopamine is more abundant than noradrenalin, quantitatively the effect of amphetamine on behavior mediated to a greater extent by the drug’s effect on dopamine than on noradrenalin. However, because all the psychostimulant drugs affect all three neurotransmitters (noradrenalin, dopamine and serotonin) the ratio of the involvement of these neurotransmitters seems to be the most important. Thus, it is possible that the rate of involvement of these neurotransmitter systems in prenatal life with respect of the involvement of the other system(s) in adulthood may play a role in these findings. It is noteworthy, that the finding showing increased number of entries to both chambers (with or without drug) of prenatally MA-exposed rats relative to prenatally saline-exposed and control rats after cocaine conditioning may suggest increase in locomotion induced by repeated cocaine administration. Note, that this increase in locomotion was apparent only during the CPP, but not in the pre-exposure session. This suggestion is further supported by simple visual comparison (see Figs. 2–4) showing that the number of entries of prenatally MA-exposed rats conditioned to cocaine is

Fig. 4. The effect of prenatal MA exposure and cocaine conditioning in the CPP test. (A) Number of entries to chambers during the CPP test; and (B) time spent in chambers during the CPP test. Values are means ± SEM. *p < 0.05 chamber with cocaine > chamber without cocaine in control and prenatally saline-exposed animals. # p < 0.05 vs control rats in the same chamber. + p < 0.05; ++ p < 0.01 vs prenatally saline-exposed rats in the same chamber. COC: cocaine.

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higher than number of entries of prenatally MA-exposed rats conditioned to MA or amphetamine. This hypothesis is supported by studies of Carey and co-workers [7,8] demonstrating increase in locomotion after several injections of cocaine in a dose of 10 mg/kg. Therefore, future studies are planned to use other behavioral tests, such as open field, to examine the increase in locomotion in prenatally MA-exposed rats administered with cocaine in adulthood. Our present data also showed that prenatally MA-exposed animals had lower weight than control or prenatally saline-exposed animals. These data may be explained by known anorectic effect of psychostimulants [40]. Already our previous studies [23,51] and also studies of others [1,31,61] demonstrated that prenatal MA exposure induces decrease in birth weight in newborn rats which may last through the entire preweaning period. Because the tested animals in each experiment were animals of the same age, it seems that the effect of prenatal MA exposure on weight persists until adulthood. This suggestion is supported by studies of Martin et al. [32] and Williams et al. [61]. It should be noted that the weight gain did not differ based on prenatal drug exposure in MA and amphetamine conditioning and was about 25% in MA experiment and about 10% in amphetamine experiment, respectively. In contrast there was no significant weight gain in prenatally MA-exposed rats during the cocaine experiment, while controls and prenatally saline-exposed rats gained about 7% in the cocaine experiment. Note that the conditioning consists of 4 days of cocaine injections in a dose of 10 mg/kg and 4 days of saline injections. Similarly to the finding of locomotion and conditioning, the reciprocal effect of prenatal methamphetamine and cocaine in adulthood seems to be the most important finding of the present study also for the weight gain. What might be the explanation? There are studies showing that cocaine- and amphetamine-regulated transcript (CART) peptide via affecting the serotonin receptors plays an important role in decrease of food intake resulting in the anorectic effect of cocaine [2,25,36]. Because, as mentioned above, serotoninergic system is the key neurotransmitter system that plays a role in this mechanism of action of cocaine, the CART peptide might be a possible explanation also for our results [15,39,43]. Thus, it is possible that prenatal MA exposure impairs the expression and/or synthesis of the CART that results in changed response to cocaine in adulthood. Studies measuring the CART and food intake in the groups of MA, amphetamine and cocaine animals that were prenatally exposed to MA may shed light on this idea. The present study further shows some changes in tail temperature in the days when amphetamine was administered. Psychostimulants are known to increase the metabolism and also the body temperature [27,34,42]. So our finding that only amphetamine but not MA or cocaine induced the increase of the tail temperature was surprising. One explanation might be in the doses used in the present study. Another explanation might be in the sympathomimetic effect of the psychostimulant drugs. As mentioned above, the ratio of amphetamine, MA and cocaine effect on noradrenergic, dopaminergic and serotoninergic system differs. Studies [15,39,43] demonstrating that the biggest influence on noradrenergic system has amphetamine relative to MA or cocaine would explain the increase of the tail temperature. This is however only a speculation that has to be further examined. The data further showed increase in defecation in days with drug administration which would suggest increased stress response. This is supported by findings demonstrating that psychostimulants increase stress response and the level of stress hormones, effect of which seems to be associated with the CART peptide [17,18,24,26]. However, the present data show some differences in the effect of psychostimulants on defecation. Specifically, while amphetamine and cocaine increased the number of boluses dropped during the 1-h conditioning in all animals regardless of prenatal exposure, MA induced this increase in defecation only in prenatally saline- and

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MA-exposed rats but did not change it in control animals. However, it should be noted that in control animals, there was increased defecation also in days without MA administration (number of boluses 7.0 ± 0.5). The finding that the increased defecation was present only in control animals without drug exposure during the MA conditioning (about 7 boluses in average) and not in the experiments with amphetamine and cocaine conditioning (about 1–2 boluses in average) was very surprising and suggested possible mistake in measurements. However, when we rechecked the data in more details, we found that the increase in defecation started on 2nd day and higher. However, if saline was injected on Day 1, the number of dropped boluses was 0–2, thereby, did not differ from the control groups in amphetamine or cocaine experiments. These findings suggest that stress induced by administration of MA persisted longer than stress induced by administration of amphetamine and cocaine, because it persisted even in the days without MA. The difference between prenatally saline-exposed and control animals in defecation in days without drugs in MA conditioning might be explained by prenatal stress induced by prenatal repeated saline injection. It was repeatedly suggested that maternal saline (placebo) injections during gestation period is considered as a mild stressor that may induce long-lasting changes in stress response in adulthood [11,37,60]. Thus, it is possible that prenatally salineexposed animals in the present study are more resistant against stress in adulthood and therefore drop less boluses in the MA CPP test than controls. It is also possible that the higher stress response of prenatally MA-exposed animals that were conditioned to MA in adulthood might affect their drug-seeking behavior in the CPP test. 5. Conclusion In conclusion, our results did not confirm our hypothesis that in the CPP test, prenatal MA exposure increases drug-seeking behavior in adulthood. However, we present some novel data shedding the light on several important questions and unresolved problems. Acknowledgments This study was supported by grant # 305/09/0126 from Grant Agency of the Czech Republic, grant # NS10509-3/2009 from Internal Agency of the Ministry of Health of the Czech, and by Research Goal # MSM 0021620816 from Ministry of Education, Youth and Sports. The procedures for animal experimentation utilized in this report was reviewed and approved by the Institutional Animal Care and Use Committee and is in agreement with the Czech Government Requirements under the Policy of Humans Care of Laboratory Animals (No. 246/1992) and with the regulations of the Ministry of Agriculture of the Czech Republic (No. 311/1997). References [1] Acuff-Smith KD, Schilling MA, Fisher JE, Vorhees CV. Stage-specific effects of prenatal d-methamphetamine exposure on behavioral and eye development in rats. Neurotoxicol Teratol 1996;18(2):199–215. [2] Aja S, Sahandy S, Ladenheim EE, Schwartz GJ, Moran TH. Intracerebroventricular CART peptide reduces food intake and alters motor behavior at a hindbrain site. Am J Physiol Regul Integr Comp Physiol 2001;281(6):R1862–7. [3] Arnold JC. The role of endocannabinoid transmission in cocaine addiction. Pharmacol Biochem Behav 2005;81(2):396–406. [4] Bartoletti M, Gaiardi M, Gubellini C, Bacchi A, Babbini M. Cross-sensitization to the excitatory effect of morphine in post-dependent rats. Neuropharmacology 1985;24(9):889–93. [5] Bonate PL, Swann A, Silverman PB. Behavioral sensitization to cocaine in the absence of altered brain cocaine levels. Pharmacol Biochem Behav 1997;57(4):665–9. [6] Bubeníková-Valeˇsová V, Kaˇcer P, Syslová K, Rambousek L, Janovsky´ M, Schutová B, et al. Prenatal methamphetamine exposure affects the mesolimbic dopaminergic system and behavior in adult offspring. Int J Dev Neurosci 2009;27(6):525–30.

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[7] Carey R, Gui J. A simple and reliable method for the positive identification of Pavlovian conditioned cocaine effects in open-field behavior. J Neurosci Methods 1997;73(1):1–8. [8] Carey RJ, Damianopoulos EN. Cocaine conditioning and sensitization: the habituation factor. Pharmacol Biochem Behav 2006;84(1):128–33. [9] Carey RJ, Gui J. Cocaine conditioning and cocaine sensitization: what is the relationship? Behav Brain Res 1998;92(1):67–76. [10] Cornish JL, Kalivas PW. Cocaine sensitization and craving: differing roles for dopamine and glutamate in the nucleus accumbens. J Addict Dis 2001;20(3):43–54. [11] Drago F, Di Leo F, Giardina L. Prenatal stress induces body weight deficit and behavioural alterations in rats: the effect of diazepam. Eur Neuropsychopharmacol 1999;9(3):239–45. [12] Estelles J, Rodriguez-Arias M, Maldonado C, Aguilar MA, Minarro J. Gestational exposure to cocaine alters cocaine reward. Behav Pharmacol 2006;17(5–6):509–15. [13] Fattore L, Deiana S, Spano SM, Cossu G, Fadda P, Scherma M, et al. Endocannabinoid system and opioid addiction: behavioural aspects. Pharmacol Biochem Behav 2005;81(2):343–59. [14] Ferrario CR, Robinson TE. Amphetamine pretreatment accelerates the subsequent escalation of cocaine self-administration behavior. Eur Neuropsychopharmacol 2007;17(5):352–7. [15] Fleckenstein AE, Gibb JW, Hanson GR. Differential effects of stimulants on monoaminergic transporters: pharmacological consequences and implications for neurotoxicity. Eur J Pharmacol 2000;406(1):1–13. [16] Gagin R, Kook N, Cohen E, Shavit Y. Prenatal morphine enhances morphineconditioned place preference in adult rats. Pharmacol Biochem Behav 1997;58(2):525–8. [17] Grace CE, Schaefer TL, Herring NR, Skelton MR, McCrea AE, Vorhees CV, et al. (+)Methamphetamine increases corticosterone in plasma and BDNF in brain more than forced swim or isolation in neonatal rats. Synapse 2008;62(2):110–21. [18] Harris DS, Reus VI, Wolkowitz OM, Mendelson JE, Jones RT. Repeated psychological stress testing in stimulant-dependent patients. Prog Neuropsychopharmacol Biol Psychiatry 2005;29(5):669–77. [19] He S, Grasing K. Chronic opiate treatment enhances both cocaine-reinforced and cocaine-seeking behaviors following opiate withdrawal. Drug Alcohol Depend 2004;75(2):215–21. [20] Heyser CJ, Goodwin GA, Moody CA, Spear LP. Prenatal cocaine exposure attenuates cocaine-induced odor preference in infant rats. Pharmacol Biochem Behav 1992;42(1):169–73. [21] Heyser CJ, Miller JS, Spear NE, Spear LP. Prenatal exposure to cocaine disrupts cocaine-induced conditioned place preference in rats. Neurotoxicol Teratol 1992;14(1):57–64. [22] Horger BA, Giles MK, Schenk S. Preexposure to amphetamine and nicotine predisposes rats to self-administer a low dose of cocaine. Psychopharmacology (Berl) 1992;107(2–3):271–6. ˇ R, Pometlová M, Rokyta R. Effect of metham[23] Hrubá L, Schutová B, Slamberová phetamine exposure and cross-fostering on sensorimotor development of male and female rat pups. Dev Psychobiol 2009;51(1):73–83. [24] Chaki S, Kawashima N, Suzuki Y, Shimazaki T, Okuyama S. Cocaine- and amphetamine-regulated transcript peptide produces anxiety-like behavior in rodents. Eur J Pharmacol 2003;464(1):49–54. [25] Jean A, Conductier G, Manrique C, Bouras C, Berta P, Hen R, et al. Anorexia induced by activation of serotonin 5-HT4 receptors is mediated by increases in CART in the nucleus accumbens. Proc Natl Acad Sci USA 2007;104(41):16335–40. [26] Koylu EO, Balkan B, Kuhar MJ, Pogun S. Cocaine and amphetamine regulated transcript (CART) and the stress response. Peptides 2006;27(8):1956–69. [27] Krasnova IN, Cadet JL. Methamphetamine toxicity and messengers of death. Brain Res Rev 2009;60(2):379–407. [28] Leri F, Flores J, Rajabi H, Stewart J. Effects of cocaine in rats exposed to heroin. Neuropsychopharmacology 2003;28(12):2102–16. [29] Liu Y, Morgan D, Roberts DC. Cross-sensitization of the reinforcing effects of cocaine and amphetamine in rats. Psychopharmacology (Berl) 2007;195(3):369–75. [30] Malanga CJ, Kosofsky BE. Does drug abuse beget drug abuse? Behavioral analysis of addiction liability in animal models of prenatal drug exposure. Brain Res Dev Brain Res 2003;147(1–2):47–57. [31] Martin JC. Effects on offspring of chronic maternal methamphetamine exposure. Dev Psychobiol 1975;8(5):397–404. [32] Martin JC, Martin DC, Radow B, Sigman G. Growth, development and activity in rat offspring following maternal drug exposure. Exp Aging Res 1976;2(3):235–51. [33] Marwick C. NIDA seeking data on effect of fetal exposure to methamphetamine. JAMA 2000;283(17):2225–6. [34] Mohaghegh RA, Soulsby ME, Skinner RD, Kennedy RH. The interaction between the central and peripheral nervous systems in mediating the thermic effect of methamphetamine. Ann N Y Acad Sci 1997;813:197–203. [35] Mueller D, Stewart J. Cocaine-induced conditioned place preference: reinstatement by priming injections of cocaine after extinction. Behav Brain Res 2000;115(1):39–47. [36] Muller CP, Carey RJ, Huston JP. Serotonin as an important mediator of cocaine’s behavioral effects. Drugs Today (Barc) 2003;39(7):497–511.

[37] Peters DA. Prenatal stress: effects on brain biogenic amine and plasma corticosterone levels. Pharmacol Biochem Behav 1982;17(4):721–5. [38] Rocha BA, Mead AN, Kosofsky BE. Increased vulnerability to self-administer cocaine in mice prenatally exposed to cocaine. Psychopharmacology (Berl) 2002;163(2):221–9. [39] Rothman RB, Baumann MH, Dersch CM, Romero DV, Rice KC, Carroll FI, et al. Amphetamine-type central nervous system stimulants release norepinephrine more potently than they release dopamine and serotonin. Synapse 2001;39(1):32–41. [40] Rothman RB, Blough BE, Baumann MH. Appetite suppressants as agonist substitution therapies for stimulant dependence. Ann N Y Acad Sci 2002;965:109– 26. [41] Sanchez CJ, Bailie TM, Wu WR, Li N, Sorg BA. Manipulation of dopamine d1like receptor activation in the rat medial prefrontal cortex alters stress- and cocaine-induced reinstatement of conditioned place preference behavior. Neuroscience 2003;119(2):497–505. [42] Sharma HS, Sjoquist PO, Ali SF. Drugs of abuse-induced hyperthermia, bloodbrain barrier dysfunction and neurotoxicity: neuroprotective effects of a new antioxidant compound H-290/51. Curr Pharm Des 2007;13(18):1903–23. [43] Shoblock JR, Sullivan EB, Maisonneuve IM, Glick SD. Neurochemical and behavioral differences between d-methamphetamine and d-amphetamine in rats. Psychopharmacology (Berl) 2003;165(4):359–69. [44] Shuster L, Yu G, Bates A. Sensitization to cocaine stimulation in mice. Psychopharmacology (Berl) 1977;52(2):185–90. ˇ [45] Schutová B, Hrubá L, Pometlová M, Deykun K, Slamberová R. Cognitive functions and drug sensitivity in adult male rats prenatally exposed to methamphetamine. Physiol Res 2009;58(5):741–50. ˇ [46] Schutová B, Hrubá L, Pometlová M, Rokyta R, Slamberová R. Responsiveness to methamphetamine in adulthood is altered by prenatal exposure in rats. Physiol Behav 2010;99(3):381–7. [47] Suto N, Austin JD, Tanabe LM, Kramer MK, Wright DA, Vezina P. Previous exposure to VTA amphetamine enhances cocaine self-administration under a progressive ratio schedule in a D1 dopamine receptor dependent manner. Neuropsychopharmacology 2002;27(6):970–9. [48] Suzuki T, Fukuoka Y, Mori T, Miyatake M, Narita M. Behavioral sensitization to the discriminative stimulus effects of methamphetamine in rats. Eur J Pharmacol 2004;498(1–3):157–61. ˇ R, Charousová P, Pometlová M. Methamphetamine administration [49] Slamberová during gestation impairs maternal behavior. Dev Psychobiol 2005;46(1):57–65. ˇ [50] Slamberová R, Mikulecká A, Pometlová M, Schutová B, Hrubá L, Deykun K. The effect of methamphetamine on social interaction of adult male rats. Behav Brain Res 2010;214(2):423–7. ˇ R, Pometlová M, Charousová P. Postnatal development of rat pups is [51] Slamberová altered by prenatal methamphetamine exposure. Prog Neuropsychopharmacol Biol Psychiatry 2006;30(1):82–8. ˇ [52] Slamberová R, Rokyta R. Occurrence of bicuculline-NMDA- and kainic acidinduced seizures in prenatally methamphetamine-exposed adult male rats. Naunyn Schmiedebergs Arch Pharmacol 2005;372(3):236–41. ˇ [53] Slamberová R, Schutová B, Bernáˇsková K, Matˇejovská I, Rokyta R. Challenge dose of methamphetamine affects kainic acid-induced seizures differently depending on prenatal methamphetamine exposure, sex, and estrous cycle. Epilepsy Behav 2010;19(1):26–31. ˇ [54] Slamberová R, Schutová B, Matˇejovská I, Bernáˇsková K, Rokyta R. Effects of a single postnatal methamphetamine administration on NMDA-induced seizures are sex- and prenatal exposure-specific. Naunyn Schmiedebergs Arch Pharmacol 2009;380(2):109–14. [55] Timár J, Gyarmati Z, Barna L, Knoll B. Differences in some behavioural effects of deprenyl and amphetamine enantiomers in rats. Physiol Behav 1996;60(2):581–7. [56] Turner CD, Bagnara JT. Endocrinology of the ovary. In: Turner CD, Bagnara JT, editors. General endocrinology. Philadelphia: W.B. Saunders Company; 1976. p. 450–95. [57] Tzschentke TM. Measuring reward with the conditioned place preference paradigm: a comprehensive review of drug effects, recent progress and new issues. Prog Neurobiol 1998;56(6):613–72. [58] Valvassori SS, Frey BN, Martins MR, Reus GZ, Schimidtz F, Inacio CG, et al. Sensitization and cross-sensitization after chronic treatment with methylphenidate in adolescent Wistar rats. Behav Pharmacol 2007;18(3):205–12. [59] Vela G, Martin S, Garcia-Gil L, Crespo JA, Ruiz-Gayo M, Javier Fernandez-Ruiz J, et al. Maternal exposure to delta9-tetrahydrocannabinol facilitates morphine self-administration behavior and changes regional binding to central mu opioid receptors in adult offspring female rats. Brain Res 1998;807(1–2):101–9. [60] Ward HE, Johnson EA, Salm AK, Birkle DL. Effects of prenatal stress on defensive withdrawal behavior and corticotropin releasing factor systems in rat brain. Physiol Behav 2000;70(3–4):359–66. [61] Williams MT, Blankenmeyer TL, Schaefer TL, Brown CA, Gudelsky GA, Vorhees CV. Long-term effects of neonatal methamphetamine exposure in rats on spatial learning in the Barnes maze and on cliff avoidance, corticosterone release, and neurotoxicity in adulthood. Brain Res Dev Brain Res 2003;147(1–2):163–75. ˇ R. Perinatal effect [62] Yamamotová A, Hrubá L, Schutová B, Rokyta R, Slamberová of methamphetamine on nociception in adult Wistar rats. Int J Dev Neurosci 2011;29(1):85–92.