Do prenatally methamphetamine-exposed adult male rats display general predisposition to drug abuse in the conditioned place preference test?

Impact of altered environment and early postnatal methamphetamine exposure on serotonin levels in the rat hippocampus during adolescence

BACKGROUND

Methamphetamine (MA) is a highly abused psychostimulant across all age groups including pregnant women. Because developing brain is vulnerable by the action of drugs, or other noxious stimuli, the aim of our study was to examine the effect of early postnatal administration of MA alone or in combination with enriched environment (EE) and/or stress of separate housing, on the levels of serotonin (5HT) in the hippocampus of male rat pups at three stages of adolescence (postnatal day (PND) 28, 35 and 45). MA (5 mg/kg/ml) was administered subcutaneously (sc) to pups (direct administration), or via mothers' milk between PND1 and PND12 (indirect administration). Controls were exposed saline (SA). Pups were exposed to EE and/or to separation from the weaning till the end of the experiment.

RESULTS

On PND 28, in sc-treated series, EE significantly increased the muted 5HT in SA pups after separation and restored the pronounced inhibition of 5HT by MA. No beneficial effect of EE was present in pups exposed to combination of MA and separation. 5HT development declined over time; EE, MA and separation had different effects on 5HT relative to adolescence stage.

CONCLUSIONS

Present study shows that MA along with environment or housing affect 5HT levels, depending on both the age and the method of application (direct or indirect). These findings extend the knowledge on the effects of MA alone and in combination with different housing conditions on the developing brain and highlight the increased sensitivity to MA during the first few months after birth.

The Adverse Effects of Prenatal METH Exposure on the Offspring: A Review

Abuse of methamphetamine (METH), an illicit psychostimulant, is a growing public health issue. METH abuse during pregnancy is on the rise due to its stimulant, anorectic, and hallucinogenic properties. METH can lead to multiple organ toxicity in adults, including neurotoxicity, cardiovascular toxicity, and hepatotoxicity. It can also cross the placental barrier and have long-lasting effects on the fetus. This review summarizes neurotoxicity, cardiovascular toxicity, hepatotoxicity, toxicity in other organs, and biomonitoring of prenatal METH exposure, as well as the possible emergence of sensitization associated with METH. We proposed the importance of gut microbiota in studying prenatal METH exposure. There is rising evidence of the adverse effects of METH exposure during pregnancy, which are of significant concern.

Prenatal opioid exposure and vulnerability to future substance use disorders in offspring

The heightened incidence of opioid use during pregnancy has resulted in unprecedented rates of neonates prenatally exposed to opioids. Prenatal opioid exposure (POE) results in significantly adverse medical, developmental, and behavioral outcomes in offspring. Of growing interest is whether POE contributes to future vulnerability to substance use disorders. The effects of POE on brain development is difficult to assess in humans, as the timing, dose, and route of drug exposure together with complex genetic and environmental factors affect susceptibility to addiction. Preclinical models of POE have allowed us to avoid methodological difficulties and confounding factors of POE in humans. Here, we review the effects of maternal opioid exposure on the developing brain with an emphasis on the neurobiological basis of drug addiction and on preclinical models of POE and their limitations. These studies have indicated that POE increases self-administration of drugs, reward-driven behaviors in the conditioned place paradigm, and locomotor sensitization. While addiction is multifaceted and vulnerability to drug addiction is still inconclusive in human studies of prenatally exposed infants, animal studies do provide a noteworthy corroboration of negative behavioral outcomes.

Intracerebroventricular microinjection of the 5-HT1F receptor agonist LY 344864 inhibits methamphetamine conditioned place preference reinstatement in rats

Relapse following a prolonged period of drug cessation is a key barrier in the treatment of methamphetamine (METH) addiction, for which pharmacological treatment exhibits little efficacy. Previous studies have suggested that this process involves alterations in levels of serotonin (5-HT) in the brain. Although the 5-HT1F receptor has been implicated in the reward pathway, its physiological functions remain unknown. In the present study, we examined the effect of the 5-HT1F agonist LY 344864 on the reinstatement of METH-seeking behavior in rats using a conditioned place preference (CPP) paradigm. The CPP paradigm was first used to determine the effective doses of LY and METH. Four groups were then conditioned with METH (5 mg/kg; i.p.), while the sham group received saline. METH-induced CPP was subsequently extinguished. On the 13th day of extinction, the rats received either METH (0, 1, or 2.5 mg/kg; i.p.) plus vehicle or priming METH plus LY (2 μg/5 μL; i.c.v.). On reinstatement day, preference scores were calculated as the difference in time spent in the drug-paired and vehicle-paired compartments. Rats conditioned with the lowest effective dose of METH (5 mg/kg) exhibited significant differences in pre- and post-testing preference scores. Preference scores were significantly higher in the saline + METH group than in the control group. Furthermore, preference scores were significantly higher in rats that had received priming METH treatment, and pre-treatment with LY significantly attenuated the reinstatement of METH-seeking behavior. These findings suggest that future studies should evaluate the therapeutic potential of 5-HT1F agonists for preventing relapse in individuals with METH addiction.

Differential behavioral effects of nicotine in adult male and female rats with a history of prenatal methamphetamine exposure

The goal of the current study was to assess the effects of prenatal methamphetamine (MA)/saline exposure on nicotine-induced stimulant and aversive effects in both male and female adult rats. The aversive effects of nicotine were assessed using the nicotine-induced conditioned taste aversion model (0.4mg/kg, base), while the stimulant effects of nicotine were measured by assessing changes in spontaneous locomotor activity after subcutaneous administration of different doses of nicotine (0, 0.1 & 0.4mg/kg, base). The aversive effects of nicotine were significantly decreased in male, but not in female rats with a history of prenatal MA exposure compared to respective saline controls. No influence of prenatal MA exposure was observed on nicotine-induced increase in locomotor activity in either male or female rats. In conclusion, males with a history of prenatal MA exposure may be more vulnerable to nicotine addiction due to a decrease in nicotine-induced aversive effects.

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

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 (5mg/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; 5mg/kg), MDMA (3,4-methylenedioxy-methamphetamine; 5mg/kg), morphine (MOR; 5mg/kg), or delta-9-tetrahydrocannabinol (THC; 2mg/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.

Prenatal morphine exposure during late embryonic stage enhances the rewarding effects of morphine and induces the loss of membrane-bound protein kinase C-α in intermediate medial mesopallium in the chick

The susceptibility to drug abuse may be associated with the structural and/or functional changes in the reward-related brain regions induced by drug exposure during sensitive periods of embryonic development. Previously, we have found that prenatal morphine exposure during embryonic days 17-20 may be crucial for developing the susceptibility to morphine reward after hatching. However, the underlying structure and cellular mechanisms need further investigation. In the present study, the chicks of a few days old, which were prenatally exposed to morphine during E17-20, obviously showed higher preference for the morphine-paired chamber and hyperactivity during the expression of morphine conditioned place preference (CPP), and the reduction in membrane-bound of PKCα of the bilateral intermediate medial mesopallium (IMM) assayed immunologically. These results indicate that the decreased expression of PKCα in IMM may participate in the development of the susceptibility to the rewarding effects of morphine in chicks prenatally exposed to morphine, and provide further support for the cross-species evolutionary concordance among amniotes.

The Effect of Prenatal Methamphetamine Exposure on Recognition Memory in Adult Rats

The use of methamphetamine (MA) among pregnant women is an increasing world-wide health problem. Prenatal MA exposure may cause changes in foetus but the exact effects have remained unclear. The aim of this study is to present the effect of prenatal MA exposure on recognition memory in adult rats. Adult female Wistar rats were injected daily with D-methamphetamine HCl (MA; 5 mg/kg, s.c.) during the entire gestation period. Control females were treated with saline in the same regime. Adult male offspring was administrated acutely by MA (1 mg/kg i.p.) or saline 30 minutes before beginning of an experiment. For testing recognition memory two tasks were chosen: Novel Object Recognition Test (NORT) and Object Location Test (OLT). Our results demonstrate that prenatally MA-exposed animals were worse in NORT independently on an acute administration of MA in adulthood. Prenatally MA-exposed rats did not deteriorate in OLT, but after acute administration of MA in adulthood, there was significant worsening compared to appropriate control. Prenatally saline-exposed offspring did not deteriorate in any test even after acute administration of MA. Our data suggest that prenatal MA exposure in rats cause impairment in recognition memory in adult offspring, but not in spatial memory. In addition, acute administration of MA to controls did not deteriorate either recognition or spatial memory.

Neurobehavioral Effects from Developmental Methamphetamine Exposure

Intrauterine methamphetamine exposure adversely affects the neurofunctional profile of exposed children, leading to a variety of higher order cognitive deficits, such as decreased attention, reduced working-memory capability, behavioral dysregulation, and spatial memory impairments (Kiblawi et al. in J Dev Behav Pediatr 34:31-37, 2013; Piper et al. in Pharmacol Biochem Behav 98:432-439 2011; Roussotte et al. in Neuroimage 54:3067-3075, 2011; Twomey et al. in Am J Orthopsychiatry 83:64-72, 2013). In animal models of developmental methamphetamine, both neuroanatomical and behavioral outcomes critically depend on the timing of methamphetamine administration. Methamphetamine exposure during the third trimester human equivalent period of brain development results in well-defined and persistent wayfinding and spatial navigation deficits in rodents (Vorhees et al. in Neurotoxicol Teratol 27:117-134, 2005, Vorhees et al. in Int J Dev Neurosci 26:599-610, 2008; Vorhees et al. in Int J Dev Neurosci 27:289-298, 2009; Williams et al. in Psychopharmacology (Berl) 168:329-338, 2003b), whereas drug delivery during the first and second trimester equivalents produces no such effect (Acuff-Smith et al. in Neurotoxicol Teratol 18:199-215, 1996; Schutova et al. in Physiol Res 58:741-750, 2009a; Slamberova et al. in Naunyn Schmiedebergs Arch Pharmacol 380:109-114, 2009, Slamberova et al. in Physiol Res 63:S547-S558, 2014b). In this review, we examine the impact of developmental methamphetamine on emerging neural circuitry, neurotransmission, receptor changes, and behavioral outcomes in animal models. The review is organized by type of effects and timing of drug exposure (prenatal only, pre- and neonatal, and neonatal only). The findings elucidate functional patterns of interconnected brain structures (e.g., frontal cortex and striatum) and neurotransmitters (e.g., dopamine and serotonin) involved in methamphetamine-induced developmental neurotoxicity.

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.

Prenatal exposure to methylphenidate affects the dopamine system and the reactivity to natural reward in adulthood in rats

BACKGROUND

Methylphenidate (MPH) is a commonly-used medication for the treatment of children with Attention-Deficit/Hyperactivity Disorders (ADHD). However, its prescription to adults with ADHD and narcolepsy raises the question of how the brain is impacted by MPH exposure during pregnancy. The goal of this study was to elucidate the long-term neurobiological consequences of prenatal exposure to MPH using a rat model.

METHODS

We focused on the effects of such treatment on the adult dopamine (DA) system and on the reactivity of animals to natural rewards.

RESULTS

This study shows that adult male rats prenatally exposed to MPH display elevated expression of presynaptic DA markers in the DA cell bodies and the striatum. Our results also suggest that MPH-treated animals could exhibit increased tonic DA activity in the mesolimbic pathway, altered signal-to-noise ratio after a pharmacological stimulation, and decreased reactivity to the locomotor effects of cocaine. Finally, we demonstrated that MPH rats display a decreased preference and motivation for sucrose.

CONCLUSIONS

This is the first preclinical study reporting long-lasting neurobiological alterations of DA networks as well as alterations in motivational behaviors for natural rewards after a prenatal exposure to MPH. These results raise concerns about the possible neurobiological consequences of MPH treatment during pregnancy.