Nicotine Exposure in a Phencyclidine-Induced Mice Model of Schizophrenia: Sex-Selective Medial Prefrontal Cortex Protein Markers of the Combined Insults in Adolescent Mice.

Tobacco misuse as a comorbidity of schizophrenia is frequently established during adolescence. However, comorbidity markers are still missing. Here, the method of label-free proteomics was used to identify deregulated proteins in the medial prefrontal cortex (prelimbic and infralimbic) of male and female mice modelled to schizophrenia with a history of nicotine exposure during adolescence. Phencyclidine (PCP), used to model schizophrenia (SCHZ), was combined with an established model of nicotine minipump infusions (NIC). The combined insults led to worse outcomes than each insult separately when considering the absolute number of deregulated proteins and that of exclusively deregulated ones. Partially shared Reactome pathways between sexes and between PCP, NIC and PCPNIC groups indicate functional overlaps. Distinctively, proteins differentially expressed exclusively in PCPNIC mice reveal unique effects associated with the comorbidity model. Interactome maps of these proteins identified sex-selective subnetworks, within which some proteins stood out: for females, peptidyl-prolyl cis-trans isomerase (Fkbp1a) and heat shock 70 kDa protein 1B (Hspa1b), both components of the oxidative stress subnetwork, and gamma-enolase (Eno2), a component of the energy metabolism subnetwork; and for males, amphiphysin (Amph), a component of the synaptic transmission subnetwork. These are proposed to be further investigated and validated as markers of the combined insult during adolescence.

Neonatal phencyclidine as a model of sex-biased schizophrenia symptomatology in adolescent mice.

Sex-biased differences in schizophrenia are evident in several features of the disease, including symptomatology and response to pharmacological treatments. As a neurodevelopmental disorder, these differences might originate early in life and emerge later during adolescence. Considering that the disruption of the glutamatergic system during development is known to contribute to schizophrenia, we hypothesized that the neonatal phencyclidine model could induce sex-dependent behavioral and neurochemical changes associated with this disorder during adolescence. C57BL/6 mice received either saline or phencyclidine (5, 10, or 20 mg/kg) on postnatal days (PN) 7, 9, and 11. Behavioral assessment occurred in late adolescence (PN48-50), when mice were submitted to the open field, social interaction, and prepulse inhibition tests. Either olanzapine or saline was administered before each test. The NMDAR obligatory GluN1 subunit and the postsynaptic density protein 95 (PSD-95) were evaluated in the frontal cortex and hippocampus at early (PN30) and late (PN50) adolescence. Neonatal phencyclidine evoked dose-dependent deficits in all analyzed behaviors and males were more susceptible. Males also had reduced GluN1 expression in the frontal cortex at PN30. There were late-emergent effects at PN50. Cortical GluN1 was increased in both sexes, while phencyclidine increased cortical and decreased hippocampal PSD-95 in females. Olanzapine failed to mitigate most phencyclidine-evoked alterations. In some instances, this antipsychotic aggravated the deficits or potentiated subthreshold effects. These results lend support to the use of neonatal phencyclidine as a sex-biased neurodevelopmental preclinical model of schizophrenia. Olanzapine null effects and deleterious outcomes suggest that its use during adolescence should be further evaluated.

Maternal protein restriction during the lactation period disrupts the ontogenetic development of behavioral traits in male Wistar rat offspring.

Neonatal undernutrition in rats results in short- and long-term behavioral and hormonal alterations in the offspring. It is not clear, however, whether these effects are present since the original insult or if they develop at some specific age later in life. Here, we assessed the ontogenetic profile of behavioral parameters associated with anxiety, exploration and memory/learning of Wistar rat offspring that were subjected to protein malnutrition during lactation. Dams and respective litters were separated into two groups: (1) protein-restricted (PR), which received a hypoproteic chow (8% protein) from birth to weaning [postnatal day (PN) 21]; (2) control (C), which received normoproteic chow. Offspring's behaviors, corticosterone, catecholamines, T3 and T4 levels were assessed at PN21 (weaning), PN45 (adolescence), PN90 (young adulthood) or PN180 (adulthood). PR offspring showed an age-independent reduction in the levels of anxiety-like behaviors in the Elevated Plus Maze and better memory performance in the Radial Arm Water Maze. PR offspring showed peak exploratory activity in the Open Field earlier in life, at PN45, than C, which showed theirs at PN90. Corticosterone was reduced in PR offspring, particularly at young adulthood, while catecholamines were increased at weaning and adulthood. The current study shows that considerable age-dependent variations in the expression of the observed behaviors and hormonal levels exist from weaning to adulthood in rats, and that protein restriction during lactation has complex variable-dependent effects on the ontogenesis of the assessed parameters.

Lifetime caffeine and adolescent nicotine exposure in mice: effects on anxiety-like behavior and reward.

Caffeine consumption occurs throughout life, while nicotine use typically begins during adolescence, the period when caffeine-nicotine epidemiological association begins in earnest. Despite that, few studies in animal models parallel the pattern of coexposure that occurs in humans. Therefore, the neurobehavioral consequences of the association between these drugs remain unclear. Here, we exposed Swiss mice to lifetime caffeine. Caffeine solutions of 0.1 g/L (CAF0.1), 0.3 g/L (CAF0.3), or water (CTRL) were used as the sole liquid source, being offered to progenitors until weaning and, after that, directly to the offspring until the last day of adolescent behavioral evaluation. The open field test was used to evaluate acute effects of nicotine, of lifetime caffeine and of their interaction on locomotion and anxiety-like behavior, while the conditioned place preference test was used to assess the impact of caffeine on nicotine (0.5 mg/Kg, i.p.) reward. Frontal cerebral cortex dopamine content, dopamine turnover, and norepinephrine levels, as well as hippocampal serotonin 1A receptor expression were assessed. CAF0.3 mice exhibited an increase in anxiety-like behavior when compared to CAF0.1 and CTRL ones, but nicotine coexposure mitigated the anxiogenic-like caffeine-induced effect. Distinctively, caffeine had no effect on locomotion and failed to interfere with both nicotine-induced hyperactivity and place preference. There were no significant effects on dopaminergic and serotonergic markers. In conclusion, although caffeine did not affect nicotine reward, considering the strong association between anxiety disorders and tobacco consumption, caffeine-induced anxiety-like behavior advises limiting its consumption during development, including adolescence, as caffeine could be a risk factor to nicotine use.

Adolescent nicotine potentiates the inhibitory effect of raclopride, a D2R antagonist, on phencyclidine-sensitized psychotic-like behavior in mice.

The association between schizophrenia and nicotine addiction becomes evident during adolescence. Here, to investigate interactive events that might underlie the early establishment of this comorbidity, we used phencyclidine-evoked locomotor sensitization, a proxy model of psychotic behavior, and nicotine minipump infusions in adolescent mice. Considering the involvement of dopamine D2 receptors in both schizophrenia and addiction, we further tested their role by exposing mice to raclopride. Adolescent mice that were either exposed to nicotine (24 mg/Kg/day) or not, received single daily raclopride (0.5 mg/kg, s.c.) or saline followed by phencyclidine injections (10 mg/Kg, s.c.) during open field testing for 6 consecutive days (Acquisition phase, ACQ). Phencyclidine and nicotine challenges (Sensitization Test, ST) were carried out after a 5-day withdrawal. Ambulation escalated in response to repeated phencyclidine exposure during ACQ and was increased after phencyclidine challenge, evidencing development and expression of locomotor sensitization. Raclopride prevented phencyclidine-evoked development of sensitization. However, raclopride pre-exposure during ACQ only shortened its expression in phencyclidine-challenged mice. Nicotine failed to interfere with phencyclidine stimulatory effects during ACQ but potentiated raclopride inhibition during the first ACQ days. During ST, nicotine history shortened the expression of phencyclidine-evoked sensitization. Nicotine challenge had no impact on locomotion, which is consistent with a lack of nicotine/phencyclidine cross-sensitization. In conclusion, our results show that nicotine does not worsen, and may even ameliorate phencyclidine-sensitized psychotic-like behavior in adolescent mice. The potentiation of raclopride-mediated inhibition further suggests that nicotine transiently improves the therapeutic efficacy of medication on psychotic symptoms through mechanisms that converge on D2 receptors.

Beneficial effects of whole-body vibration exercise for brain disorders in experimental studies with animal models: a systematic review.

Brain disorders have been a health challenge and is increasing over the years. Early diagnosis and interventions are considered essential strategies to treat patients at risk of brain disease. Physical exercise has shown to be beneficial for patients with brain diseases. A type of exercise intervention known as whole-body vibration (WBV) exercise gained increasing interest. During WBV, mechanical vibrations, produced by a vibrating platform are transmitted, to the body. The purpose of the current review was to summarize the effects of WBV exercise on brain function and behavior in experimental studies with animal models. Searches were performed in EMBASE, PubMed, Scopus and Web of Science including publications from 1960 to July 2021, using the keywords "whole body vibration" AND (animal or mice or mouse or rat or rodent). From 1284 hits, 20 papers were selected. Rats were the main animal model used (75%) followed by mice (20%) and porcine model (5%), 16 studies used males species and 4 females. The risk of bias, accessed with the SYRCLE Risk of Bias tool, indicated that none of the studies fulfilled all methodological criteria, resulting in possible bias. Despite heterogeneity, the results suggest beneficial effects of WBV exercise on brain functioning, mainly related to motor performance, coordination, behavioral control, neuronal plasticity and synapse function. In conclusion, the findings observed in animal studies justifies continued clinical research regarding the effectiveness and potential of WBV for the treatment of various types of brain disorders such as trauma, developmental disorders, neurogenetic diseases and other neurological diseases.

Does nicotine exposure during adolescence modify the course of schizophrenia-like symptoms? Behavioral analysis in a phencyclidine-induced mice model.

The first symptoms of schizophrenia (SCHZ) are usually observed during adolescence, a developmental period during which first exposure to psychoactive drugs also occurs. These epidemiological findings point to adolescence as critical for nicotine addiction and SCHZ comorbidity, however it is not clear whether exposure to nicotine during this period has a detrimental impact on the development of SCHZ symptoms since there is a lack of studies that investigate the interactions between these conditions during this period of development. To elucidate the impact of a short course of nicotine exposure across the spectrum of SCHZ-like symptoms, we used a phencyclidine-induced adolescent mice model of SCHZ (2.5mg/Kg, s.c., daily, postnatal day (PN) 38-PN52; 10mg/Kg on PN53), combined with an established model of nicotine minipump infusions (24mg/Kg/day, PN37-44). Behavioral assessment began 4 days after the end of nicotine exposure (PN48) using the following tests: open field to assess the hyperlocomotion phenotype; novel object recognition, a declarative memory task; three-chamber sociability, to verify social interaction and prepulse inhibition, a measure of sensorimotor gating. Phencyclidine exposure evoked deficits in all analyzed behaviors. Nicotine history reduced the magnitude of phencyclidine-evoked hyperlocomotion and impeded the development of locomotor sensitization. It also mitigated the deficient sociability elicited by phencyclidine. In contrast, memory and sensorimotor gating deficits evoked by phencyclidine were neither improved nor worsened by nicotine history. In conclusion, our results show for the first time that nicotine history, restricted to a short period during adolescence, does not worsen SCHZ-like symptoms evoked by a phencyclidine-induced mice model.

Forced swimming stress increases natatory activity of lead-exposed mice.

Recent evidence points to the relationship between lead toxicity and the function of the hypothalamic-pituitary-adrenal axis, which suggests that lead exposure could influence how an individual cope with stress. Here we test this hypothesis by investigating the behavioral effects of lead exposure in mice during the forced swimming test (FST), a parading in which animals are exposed to a stressful situation and environment. Swiss mice received either 180 ppm or 540 ppm of lead acetate (Pb) in their ad-lib water supply for 60-90 days, starting at postnatal day 30. Control (Ctrl) mice drank tap water. At the end of the exposure period, mice were submitted to a 5-min session of FST or to an open-field session of the same duration. Data from naïve animals showed that corticosterone levels were higher for animals tested in the FST compared to animals tested in the open-field. Blood-lead levels (BLL) in Pb-exposed mice ranged from 14.3 to 106.9 µg/dL. No differences were observed in spontaneous locomotion between Ctrl and Pb-exposed groups in the open-field. However, in the FST, Pb-treated mice displayed higher swimming activity than Ctrl ones and this effect was observed even for animals with BLL higher than 20 µg/dL. Furthermore, significant differences in brain glutathione levels, used as an indicator of led toxicity, were only observed for BLL higher than 40 µg/dL. Overall, these findings suggest that swimming activity in the FST is a good indicator of lead toxicity and confirm our prediction that lead toxicity influences behavioral responses associated to stress.

Sex- and age-dependent differences in nicotine susceptibility evoked by developmental exposure to tobacco smoke and/or ethanol in mice.

Either tobacco smoking or alcohol consumption during pregnancy sex-selectively increases susceptibility to drugs of abuse later in life. Considering that pregnant smoking women are frequently intermittent consumers of alcoholic beverages, here, we investigated whether a short-term ethanol exposure restricted to the brain growth spurt period when combined with chronic developmental exposure to tobacco smoke aggravates susceptibility to nicotine in adolescent and adult mice. Swiss male and female mice were exposed to tobacco smoke (SMK; research cigarettes 3R4F, whole-body exposure, 8 h/daily) or ambient air during the gestational period and until the tenth postnatal day (PN). Ethanol (ETOH, 2 g/Kg, 25%, i.p.) or saline was injected in the pups every other day from PN2 to PN10. There were no significant differences in cotinine (nicotine metabolite) and ethanol serum levels among SMK, ETOH and SMK + ETOH groups. During adolescence (PN30) and adulthood (PN90), nicotine (NIC, 0.5 mg/Kg) susceptibility was evaluated in the conditioned place preference and open field tests. NIC impact was more evident in females: SMK, ETOH and SMK + ETOH adolescent females were equally more susceptible to nicotine-induced place preference than control animals. At adulthood, SMK and SMK + ETOH adult females exhibited a nicotine-evoked hyperlocomotor profile in the open field, with a stronger effect in the SMK + ETOH group. Our results indicate that ethanol exposure during the brain growth spurt, when combined to developmental exposure to tobacco smoke, increases nicotine susceptibility with stronger effects in adult females. This result represents a worsened outcome from the early developmental dual exposure and may predispose nicotine use/abuse later in life.

Mood-related behavioral and neurochemical alterations in mice exposed to low chlorpyrifos levels during the brain growth spurt.

Organophosphates are among the most used pesticides. Particularly, chlorpyrifos (CPF) is responsible for a number of deleterious effects on brain development, which may program behavioral changes later in life. Here, we investigated whether a regimen of early low level CPF exposure that did not result in a significant inhibition of acetylcholinesterase (AChE) had deleterious effects on mood-related behaviors, as well as on cholinergic and serotonergic biomarkers in the mice brain. From the 3rd to 9th postnatal day (PN), male and female Swiss mice were subcutaneously injected with CPF. Mice were submitted to a battery of behavioral tests from PN60 to PN63: open field, elevated plus maze and forced swimming tests. The cholinergic and serotonergic biomarkers were assessed at PN10 and PN63. Our data indicated that early CPF exposure increased anxiety-like behavior in females and altered decision-making behavior in both sexes. Most biochemical alterations were sex-dependent and restricted to females. At PN10, CPF female mice showed increased serotonin and choline transporter binding in cerebral cortex. Distinctively, in adult females, the effects indicated a hypoactive state: CPF exposure reduced 5-HT1a receptor binding in cerebral cortex, as well as serotonin transporter binding and choline acetyltransferase activity in brainstem. Our results indicate that CPF exposure during the brain growth spurt deregulates serotonergic and cholinergic biomarkers. The effects are consistent with impaired synaptic function, may be related to long-term mood disorders and point out to higher female susceptibility.

Ethanol exposure during the brain growth spurt period increases ethanol-induced aggressive behavior in adolescent male mice.

Ethanol exposure during development is associated with deficient social behavior, such as aggressive behavior, and ethanol consumption is associated with violent crimes, thus raising the possibility that individuals with fetal alcohol spectrum disorder may exhibit exacerbated social deficits in response to ethanol exposure. The present study evaluated the effects of ethanol exposure during the brain growth spurt period (i.e., a critical time period during which ethanol's effects are augmented) on aggressive behavior and ethanol-induced aggression during adolescence. From postnatal Day 2 (PD2) to PD8, Swiss mice received either ethanol (5 g/kg, i.p.) or saline on alternate days. On PD39, aggressive behavior was assessed using the resident-intruder paradigm in male mice, and social dominance was investigated using the tube dominance test in both males and females. Testis structure and testosterone levels were evaluated in male mice. Early ethanol exposure increased the gonadosomatic index and the number of Leydig cells. The thickness of the seminiferous tube decreased. No difference in testosterone levels was found. The ethanol-exposed resident mice exhibited increased number and duration of aggressive episodes only when challenged with a low ethanol dose (1 g/kg) before confrontation. Female mice early-exposed to ethanol won more confrontations in the tube dominance test. The present findings suggest a critical brain growth spurt period that is susceptible to ethanol-induced alterations of social dominance behavior in females. Although basal levels of aggression were unaffected, early ethanol exposure resulted in greater susceptibility to ethanol-induced aggression in adolescent male mice.

Ethanol exposure during the brain growth spurt affects social behavior and increases susceptibility to acute ethanol effects during adolescence in male mice.

The brain is particularly vulnerable to ethanol effects during its growth spurt. Outcomes of early ethanol exposure such as hyperactivity have been extensively investigated; however, persons with fetal alcohol spectrum disorder frequently have social impairments and are heavy drinkers. Despite that, scant information is available regarding the neurobiological basis of these latter behavioral issues. Here, Swiss mice exposed to ethanol (Etoh, 5 g/kg i.p., alternate days) or saline during the brain growth spurt [postnatal day (PN) 2 to 8] were used to assess social behavior after an ethanol challenging during adolescence. At PN39, animals were administered with a single ethanol dose (1 g/Kg) or water by gavage and were then evaluated in the three-chamber sociability test. We also evaluated corticosterone serum levels and the frontal cerebral cortex serotoninergic system. Etoh males showed reductions in sociability. Ethanol challenging reverted these alterations in social behavior, reduced corticosterone levels, and increased the 5-HT2 receptor binding of male Etoh mice. No alterations were observed in 5-HT and 5-HIAA contents. These data support the idea that ethanol exposure during the brain growth spurt impacts social abilities during adolescence, alters ethanol reexposure effects, and suggests that stress response and serotoninergic system play roles in this phenomenon.

Lifelong exposure to caffeine increases anxiety-like behavior in adult mice exposed to tobacco smoke during adolescence.

Caffeine and tobacco smoke are among the most frequently self-administered licit psychoactive drugs in the world. Both drugs affect anxiety levels, however, little is known on the impact of the dual exposure in the adolescent brain, the period during which smoking begins. Considering that anxiety is a relevant factor for smoking maintenance and relapse, we investigated the effects of lifelong exposure to caffeine on anxiety levels of Swiss mice exposed to tobacco smoke during adolescence. Caffeine was administrated during all prenatal and postnatal life (CAF, 0.1 g/l to drink). From postnatal day 30-45, animals were exposed to tobacco smoke (SMK, whole body exposure, 8 h/day) generated from research cigarettes type 3R4F (nicotine = 0.73 mg/per cigarette). Four groups were analyzed: (1) CAF + SMK exposure; (2) SMK exposure; (3) CAF exposure; (4) Control. Anxiety levels were assessed in the elevated plus maze at the end of smoke exposure (PN45), at short- (PN55) and long-term (PN75) withdrawal. Caffeine exposure reduced decision making time (time in center of maze) during adolescence (PN45 and PN55). In addition, caffeine increased anxiety-like behavior during long-term tobacco smoke withdrawal. The present study provides experimental evidence that caffeine and tobacco smoke during adolescence interact resulting in emotional dysregulation during tobacco smoke withdrawal. Particularly, increased anxiety-like behavior during long-term withdrawal in CAF + SMK animals demonstrates late-emergent effects. In this sense, our data suggest that lifelong caffeine exposure may be an important factor in tobacco relapse.

Tobacco smoke and ethanol during adolescence: Both combined- and single-drug exposures lead to short- and long-term disruption of the serotonergic system in the mouse brain.

The impairment of the serotonergic system contributes to nicotine and ethanol effects on mood, suggesting that this system is targeted by each of these drugs and that co-exposure possibly worsens the disruption. Here, we tested this hypothesis in an adolescent mice model of tobacco smoke and/or ethanol exposure. From postnatal day (PN) 30-45, Swiss mice were exposed to one of the following: 1) tobacco smoke (SMK; research cigarettes 2R1F, whole-body exposure, 8 h/daily); 2) ethanol (ETOH; 2 g/kg i.p., every other day); 3) SMK + ETOH; 4) Control (VEH). At PN45 (end-of-exposure), hippocampal serotonin transporter (5 H TT) binding was increased in SMK and decreased in ETOH male mice. At PN50 (short-term deprivation), cortical 5 H TT was reduced in all drug-exposed mice. In the hippocampus, similar deficits were identified in females. In both brain regions, the effects of SMK + ETOH deprivation on 5 H TT were equivalent to the damage caused by either drug. At PN50, hippocampal 5 H T1A receptor binding was reduced in ETOH and SMK + ETOH mice. Similar results were observed in the male cortex. In females, deficits were identified in SMK mice. In both brain regions, SMK + ETOH 5 H T1A deficits reflected the summation of SMK and ETOH outcomes. At PN75 (long-term deprivation), there was a late-emergent increase in cortical 5 H T1A binding in SMK mice, while cortical 5 H T2 receptor binding was similarly increased in SMK and SMK + ETOH groups. Adolescent SMK and/or ETOH serotonergic impairment is sex-dependent and most evident during short-term deprivation. SMK + ETOH deprivation evokes serotonergic disruption that is at least equivalent to that caused by either drug alone.

Hyperactivity and memory/learning deficits evoked by developmental exposure to nicotine and/or ethanol are mitigated by cAMP and cGMP signaling cascades activation.

Pregnant smoking women are frequently episodic drinkers. Here, we investigated whether ethanol exposure restricted to the brain growth spurt period when combined with chronic developmental exposure to nicotine aggravates memory/learning deficits and hyperactivity, and associated cAMP and cGMP signaling disruption. To further investigate the role of these signaling cascades, we verified whether vinpocetine (a phosphodiesterase inhibitor) ameliorates the neurochemical and behavioral outcomes. Swiss mice had free access to nicotine (NIC, 50 µg/ml) or water to drink during gestation and until the 8th postnatal day (PN8). Ethanol (ETOH, 5 g/kg, i.p.) or saline were injected in the pups every other day from PN2 to PN8. At PN30, animals either received vinpocetine (20 mg/kg, i.p.) or vehicle before being tested in the step-down passive avoidance or open field. Memory/learning was impaired in NIC, ETOH and NIC + ETOH mice, and vinpocetine mitigated ETOH- and NIC + ETOH-induced deficits. Locomotor hyperactivity identified in ETOH and NIC + ETOH mice was ameliorated by vinpocetine. While cyclic nucleotides levels in cerebral cortex and hippocampus were reduced by NIC, ETOH and NIC + ETOH, this outcome was more consistent in the latter group. As observed for behavior, vinpocetine normalized NIC + ETOH nucleotides levels. pCREB levels were also increased in response to vinpocetine, with stronger effects in the NIC + ETOH group. Exposure to both drugs of abuse worsens behavioral and neurochemical disruption. These findings and the amelioration of deleterious effects by vinpocetine support the idea that cAMP and cGMP signaling contribute to nicotine- and ethanol-induced hyperactivity and memory/learning deficits.

Maternal undernutrition during lactation alters nicotine reward and DOPAC/dopamine ratio in cerebral cortex in adolescent mice, but does not affect nicotine-induced nAChRs upregulation.

Early undernutrition causes long lasting alterations that affect the response to psychoactive drugs. Particularly, undernutrition during lactation affects the acute locomotor response to nicotine during adolescence, but the reward effect of continued exposure to nicotine remains unknown. The goal of this study was to investigate the effects of undernutrition during lactation on the nicotine susceptibility indexed via conditioned place preference (CPP), on dopamine content and turnover and on nicotine-induced nicotinic cholinergic receptor (nAChR) upregulation in the cerebral cortex, midbrain and hippocampus of adolescent mice. The impact of undernutrition and nicotine exposure on stress-related hormones and leptin was also investigated. From postnatal day 2 (PN2) to weaning (PN21), dams were randomly assigned to one of the following groups: Control (C) - free access to standard laboratory diet (23% protein); Protein Restricted (PR) - free access to isoenergenetic diet (8% protein); Calorie Restricted (CR) - access to standard laboratory diet in restricted quantities (mean ingestion of PR). PR and CR groups showed less mass gain and less visceral fat mass. While C and CR were equally susceptible to nicotine-induced place preference conditioning, PR failed to show a conditioning pattern. In contrast, all groups presented a nicotine-evoked nAChR upregulation in the cerebral cortex. While dopamine and DOPAC levels did not differ between groups, the DOPAC/dopamine ratio was increased in CR animals. No differences in endocrine parameters were observed. Taken together, our results indicate that undernutrition during lactation programs for brain alterations later in life. Our data also suggest that early undernutrition does not affect the rewarding associative properties of nicotine at adolescence.

Tobacco and alcohol use during adolescence: Interactive mechanisms in animal models.

There is a strong association between tobacco smoking and the consumption of alcoholic beverages. When compared to the effects of either drug on its own, the combined use may lead to worsened outcomes, such as less successful quitting attempts and increased likelihood of developing mood disorders. Co-consumption most frequently begins during adolescence, a developmental period that is characterized by an increased risk for substance use disorders. However, to date, most studies that have contributed to the current state of knowledge on the mechanisms that underlie tobacco or alcohol use/abuse, and their consequences, adopted adult animal models. Besides, the available literature hardly addresses the effects of co-exposure, irrespective of age. Since adolescence is a period of transition between infancy and adulthood that is characterized by unique brain maturational events and behavioral traits, the mechanisms that drive drug use/abuse in adolescents differ in several aspects from those proposed to underlie adult consumption. This review summarizes and consolidates recent findings on common molecular targets and neuropharmacological mechanisms of action associated with nicotine/tobacco smoke and ethanol co-exposure in animal models, highlighting the effects that culminate in behavioral dysfunctions. To that effect, we discuss the role of mesocorticolimbic system maturation events, cross-tolerance and cross-reinforcement, stress, and sex differences in the context of adolescent co-exposure, identifying gaps in knowledge regarding the interactions between these habit-forming drugs. Finally, we suggest future directions for research on epigenetic mechanisms associated with nicotine and ethanol co-exposure as well as on potential pharmacological therapies for co-addiction.

Energy drink enhances the behavioral effects of alcohol in adolescent mice.

Mixing alcohol with energy drinks has become increasingly popular among teenagers and young adults due to the prevailing view that the stimulant properties of energy drinks decrease the depressant effects of alcohol. Surprisingly, in spite of energy drinks being heavily marketed to and consumed by adolescents, there is scarcely available preclinical data on the neurobehavioral effects of energy drinks mixed with alcohol during adolescence. Thus, here we examine the effects of the combined exposure to alcohol and energy drink on adolescent mice using a variety of behavioral tasks to assess locomotor activity, righting reflex and motor coordination. At postnatal day 40, male and female Swiss mice were assigned to the following experimental groups: alcohol diluted in energy drink (Ed+Etoh), alcohol diluted in water (Etoh) or controls (Ctrl: energy drink or water). Alcohol and energy drink (Red Bull) concentrations were 4g/kg and 8ml/kg, respectively, and all solutions were administered via oral gavage. When compared to Etoh mice, Ed+Etoh animals displayed greater locomotor activity and increased anxiety-like behaviors in the open-field, lost their righting reflexes sooner and displayed poorer motor coordination in the rotarod. Collectively, our findings indicate that alcohol-induced deficits in adolescent mice are worsened by energy drink and go against the view that the stimulant properties of energy drinks can antagonize the adverse effects of alcohol.

A ten fold reduction of nicotine yield in tobacco smoke does not spare the central cholinergic system in adolescent mice.

The tobacco industry has gradually decreased nicotine content in cigarette smoke but the impact of this reduction on health is still controversial. Since the central cholinergic system is the primary site of action of nicotine, here, we investigated the effects of exposure of adolescent mice to tobacco smoke containing either high or low levels of nicotine on the central cholinergic system and the effects associated with cessation of exposure. From postnatal day (PN) 30 to 45, male and female Swiss mice were exposed to tobacco smoke (whole body exposure, 8h/day, 7 days/week) generated from 2R1F (HighNic group: 1.74mg nicotine/cigarette) or 4A1 (LowNic group: 0.14mg nicotine/cigarette) research cigarettes, whereas control mice were exposed to ambient air. Cholinergic biomarkers were assessed in the cerebral cortex and midbrain by the end of exposure (PN45), at short- (PN50) and long-term (PN75) deprivation. In the cortex, nicotinic cholinergic receptor upregulation was observed with either type of cigarette. In the midbrain, upregulation was detected only in HighNic mice and remained significant in females at short-term deprivation. The high-affinity choline transporter was reduced in the cortex: of HighNic mice by the end of exposure; of both HighNic and LowNic females at short-term deprivation; of LowNic mice at long-term deprivation. These decrements were separable from effects on choline acetyltransferase and acetylcholinesterase activities, suggesting cholinergic synaptic impairment. Here, we demonstrated central cholinergic alterations in an animal model of tobacco smoke exposure during adolescence. This system was sensitive even to tobacco smoke with very low nicotine content.

Locomotor response to acute nicotine in adolescent mice is altered by maternal undernutrition during lactation.

Undernutrition during brain development causes long lasting alterations in different neurotransmitter systems that may alter responses to psychoactive drugs. Despite the recognized effects of early undernutrition on the cholinergic system, no evidence that demonstrates the influence of this insult on nicotine susceptibility has been reported. We investigated the effects of protein/calorie restriction during lactation on the susceptibility to nicotine in adolescent mice. Dams were randomly assigned to one of the following groups: Control (C, 20 litters)--free access to standard laboratory diet (23% protein); Protein Restricted (PR, 12 litters)--free access to a isoenergetic, 8% protein diet; Calorie Restricted (CR, 12 litters)--access to standard laboratory diet in restricted quantities (mean ingestion of PR: pair-fed group). Undernutrition extended from postnatal day 2 (PN2) to weaning (PN21). At PN30, animals either received an i.p. injection of nicotine (0.5mg/Kg) or saline and were immediately placed in open field (OF). After the OF, adrenal glands and serum were collected for the analyses of stress-related endocrine parameters and leptin concentration. PR and CR offspring showed less body mass gain and visceral fat mass. PR offspring presented reduced serum leptin concentration. In the OF, nicotine increased locomotor activity of C and PR, but not of CR. CR and PR offspring showed decreased adrenal catecholamine content, which was not dependent on nicotine exposure. Our results indicate that early undernutrition interferes with nicotine-elicited locomotor effects in adolescent mice and suggest that endocrine parameters alterations in malnourished animals do not influence the behavioral response to nicotine.