Effects of prenatal exposure to the CB-1 receptor agonist WIN 55212-2 or CO on the GABAergic neuronal systems of rat cerebellar cortex

Effects of prenatal alcohol and delta-9-tetrahydrocannabinol exposure via electronic cigarettes on motor development

BACKGROUND

Prenatal alcohol exposure can lead to a wide range of neurological and behavioral deficits, including alterations in motor domains. However, much less is known about the effects of prenatal cannabis exposure on motor development, despite cannabis being the most consumed illicit drug among women. Cannabis use among pregnant women has become increasingly popular given the widespread perception that consumption is safe during pregnancy. Moreover, alcohol and cannabis are commonly used together, even among pregnant women. Yet few studies have explored the potential consequences of combined prenatal exposure on behavioral domains.

METHODS

Using our previously established model, during gestational days 5 to 20, four groups of pregnant Sprague-Dawley rats were exposed to vaporized alcohol, delta-9-Tetrahydrocannabinol (THC) via electronic (e-) cigarettes, the combination of alcohol and THC, or a vehicle. Following birth, offspring were tested on early sensorimotor development, adolescent motor coordination, and adolescent activity levels.

RESULTS

Prenatal THC e-cigarette exposure delayed sensorimotor development early in life and impaired motor coordination later in early adolescence; combined prenatal alcohol and THC exposure did not have additive effects on sensorimotor development. However, combined prenatal exposure produced hyperactivity among male offspring.

CONCLUSIONS

Prenatal cannabis exposure may lead to impaired motor skills throughout early development and combined exposure with alcohol during gestation may lead to hyperactivity in early adolescence. These findings have important implications for informing pregnant women of the risks to the fetus associated with prenatal cannabis exposure, with and without alcohol, and could influence public policy.

The effects of prenatal nicotine and THC E-cigarette exposure on motor development in rats

RATIONALE

In the USA, nicotine and cannabis are the most common licit and illicit drugs used among pregnant women. Importantly, nicotine and cannabis are now being combined for consumption via e-cigarettes, an increasingly popular delivery device. Both nicotine and tetrahydrocannabinol (THC), the primary psychoactive component of cannabis, cross the placenta barrier. However, the consequences of prenatal cannabis use are not well understood, and less is known about potential combination effects when consumed with nicotine, especially via e-cigarettes.

OBJECTIVE

The present study used a rodent model to examine how prenatal e-cigarette exposure to nicotine, THC, and the combination impacts motor development among offspring.

METHODS

Pregnant Sprague-Dawley rats were exposed to nicotine (36 mg/mL), THC (100 mg/mL), the combination, or vehicle via e-cigarette inhalation from gestational days (GD) 5-20. One sex pair per litter was tested on an early sensorimotor development task (postnatal days [PD] 12-20) and a parallel bar motor coordination task (PD 30-32).

RESULTS

Combined prenatal exposure to nicotine and THC delayed sensorimotor development, even though neither drug produced impairments on their own. In contrast, prenatal exposure to either nicotine or THC impaired motor coordination, whereas combined exposure exacerbated these effects, particularly among females.

CONCLUSIONS

These data illustrate that prenatal exposure to either nicotine or THC may alter motor development, and that the combination may produce more severe effects. These findings have important implications for pregnant women as we better understand the teratogenic effects of these drugs consumed via e-cigarettes.

Effects of Cannabinoid Exposure during Neurodevelopment on Future Effects of Drugs of Abuse: A Preclinical Perspective

The endocannabinoid system plays a central role in the earliest stages of embryonic, postnatal and adolescent neurodevelopment. Aberrant activity of this system at key developmental phases has been shown to affect neural development. The aim of this review is to synthesise and analyse preclinical insights within rodent populations, focusing on the effects that perinatal (embryonic, gestational and early postnatal developmental stages) and adolescent (postnatal day 21–60) cannabinoid exposure impose across time on the subsequent activity of various drugs of abuse. Results in rodents show that exposure to cannabinoids during the perinatal and adolescent period can lead to multifaceted behavioural and molecular changes. In the perinatal period, significant effects of Δ⁹-THC exposure on subsequent opiate and amphetamine reward-related behaviours were observed primarily in male rodents. These effects were not extended to include cocaine or alcohol. In adolescence, various cannabinoid agonists were used experimentally. This array of cannabinoids demonstrated consistent effects on opioids across sex. In contrast, no significant effects were observed regarding the future activity of amphetamines and cocaine. However, these studies focused primarily on male rodents. In conclusion, numerous gaps and limitations are apparent in the current body of research. The sparsity of studies analysing the perinatal period must be addressed. Future research within both periods must also focus on delineating sex-specific effects, moving away from a male-centric focus. Studies should also aim to utilise more clinically relevant cannabinoid treatments.

Lipopolysaccharide-Induced Systemic Inflammation in the Neonatal Period Increases Microglial Density and Oxidative Stress in the Cerebellum of Adult Rats

Inflammatory processes occurring in the perinatal period may affect different brain regions, resulting in neurologic sequelae. Injection of lipopolysaccharide (LPS) at different neurodevelopmental stages produces long-term consequences in several brain structures, but there is scarce evidence regarding alterations in the cerebellum. The aim of this study was to evaluate the long-term consequences on the cerebellum of a systemic inflammatory process induced by neonatal LPS injection. For this, neonatal rats were randomly assigned to three different groups: naïve, sham, and LPS. Saline (sham group) or LPS solution (1 mg/kg) was intraperitoneally injected on alternate postnatal days (PN) PN1, PN3, PN5, and PN7. Spontaneous activity was evaluated with the open field test in adulthood. The cerebellum was evaluated for different parameters: microglial and Purkinje cell densities, oxidative stress levels, and tumor necrosis factor alpha (TNF-α) mRNA expression. Our results show that administration of LPS did not result in altered spontaneous activity in adult animals. Our data also indicate increased oxidative stress in the cerebellum, as evidenced by an increase in superoxide fluorescence by dihydroethidium (DHE) indicator. Stereological analyses indicated increased microglial density in the cerebellum that was not accompanied by Purkinje cell loss or altered TNF-α expression in adult animals. Interestingly, Purkinje cells ectopically positioned in the granular and molecular layers of the cerebellum were observed in animals of the LPS group. Our data suggest that neonatal LPS exposure causes persistent cellular and molecular changes to the cerebellum, indicating the susceptibility of this region to systemic inflammatory insults in infancy. Further investigation of the consequences of these changes and the development of strategies to avoid those should be subject of future studies.

Altered motor development following late gestational alcohol and cannabinoid exposure in rats

Cannabis is the most commonly used illicit drug among pregnant women, and rates are likely to increase given recent legalization. In addition, half of pregnant women who report consuming cannabis also report drinking alcohol. However, little is known about the consequences of prenatal cannabis alone or in combination with alcohol, particularly with cannabis products that are continually increasing in potency of the primary psychoactive constituent in cannabis, Δ9-tetrahydrocannabinol (THC). The current study investigated the effects of early exposure to cannabinoids during the brain growth spurt on early physical and motor development alone (Experiment 1) or in combination with alcohol (Experiment 2). In Experiment 1, Sprague-Dawley rat pups were exposed to a cannabinoid receptor agonist (CP-55,940 [CP]; 0.1, 0.25, 0.4 mg/kg/day), the drug vehicle, or a saline control from postnatal days (PD) 4-9. In Experiment 2, rat pups were exposed to CP (0.4 mg/kg/day) or the vehicle, and were additionally intubated with alcohol (11.9% v/v; 5.25 g/kg/day) or received a sham intubation. Subjects in both experiments were tested on a motor development task (PD 12-20) and a motor coordination task during adolescence (PD 30-32). Both developmental cannabinoid and alcohol exposure separately decreased body growth throughout development, and combined exposure exacerbated these effects, although only alcohol exposure induced long-term body weight reductions. Developmental cannabinoid exposure advanced early motor development, whereas alcohol exposure delayed development, and subjects given combined exposure did not differ from controls on some measures. Alcohol exposure impaired motor coordination later in life. In contrast, cannabinoid exposure, by itself, did not significantly affect long-term motor coordination, but did exacerbate alcohol-related impairments in motor coordination among females. These results suggest that cannabinoid exposure may not only alter development by itself, but may exacerbate alcohol's teratogenic effects in specific behavioral domains. These findings have important implications not only for individuals affected by prenatal exposure, but also for establishing public policy for women regarding cannabis use during pregnancy.

Long-lasting alterations of hippocampal GABAergic neurotransmission in adult rats following perinatal Δ9-THC exposure

The long-lasting effects of gestational cannabinoids exposure on the adult brain of the offspring are still controversial. It has already been shown that pre- or perinatal cannabinoids exposure induces learning and memory disruption in rat adult offspring, associated with permanent alterations of cortical glutamatergic neurotransmission and cognitive deficits. In the present study, the risk of long-term consequences induced by perinatal exposure to cannabinoids on rat hippocampal GABAergic system of the offspring, has been explored. To this purpose, pregnant rats were treated daily with Delta⁹-tetrahydrocannabinol (Δ⁹-THC; 5mg/kg) or its vehicle. Perinatal exposure to Δ⁹-THC induced a significant reduction (p<0.05) in basal and K⁺-evoked [³H]-GABA outflow of 90-day-old rat hippocampal slices. These effects were associated with a reduction of hippocampal [³H]-GABA uptake compared to vehicle exposed group. Perinatal exposure to Δ⁹-THC induced a significant reduction of CB1 receptor binding (B_max) in the hippocampus of 90-day-old rats. However, a pharmacological challenge with either Δ⁹-THC (0.1μM) or WIN55,212-2 (2μM), similarly reduced K⁺-evoked [³H]-GABA outflow in both experimental groups. These reductions were significantly blocked by adding the selective CB1 receptor antagonist SR141716A. These findings suggest that maternal exposure to cannabinoids induces long-term alterations of hippocampal GABAergic system. Interestingly, previous behavioral studies demonstrated that, under the same experimental conditions as in the present study, perinatal cannabinoids exposure induced cognitive impairments in adult rats, thus resembling some effects observed in humans. Although it is difficult and sometimes misleading to extrapolate findings obtained from animal models to humans, the possibility that an alteration of hippocampus aminoacidergic transmission might underlie, at least in part, some of the cognitive deficits affecting the offspring of marijuana users, is supported.

Stereological study of the effects of maternal diabetes on cerebellar cortex development in rat

Diabetes during pregnancy is associated with the deficits in balance and motor coordination and altered social behaviors in offspring. In the present study, we have investigated the effect of maternal diabetes and insulin treatment on the cerebellar volume and morphogenesis of the cerebellar cortex of rat neonates during the first two postnatal weeks. Sprague Dawley female rats were maintained diabetic from a week before pregnancy through parturition. At the end of pregnancy, the male offspring euthanized on postnatal days (P) 0, 7, and 14. Cavalieri's principle and fractionator methods were used to estimate the cerebellar volume, the thickness and the number of cells in the different layers of the cerebellar cortex. In spite of P0, there was a significant reduction in the cerebellar volume and the thickness of the external granule, molecular, and internal granule layers between the diabetic and the control animals. In diabetic group, the granular and purkinje cell densities were increased at P0. Moreover, the number of granular and purkinje cells in the cerebellum of diabetic neonates was reduced in comparison with the control group at P7 and P14. There were no significant differences in either the volume and thickness or the number of cells in the different layers of the cerebellar cortex between the insulin-treated diabetic group and controls. Our data indicate that diabetes in pregnancy disrupts the morphogenesis of cerebellar cortex. This dysmorphogenesis may be part of the cascade of events through which diabetes during pregnancy affects motor coordination and social behaviors in offspring.

Long-term consequences of perinatal and adolescent cannabinoid exposure on neural and psychological processes

Marihuana is the most widely consumed illicit drug, even among adolescents and pregnant women. Given the critical developmental processes that occur in the adolescent and fetal nervous system, marihuana consumption during these stages may have permanent consequences on several brain functions in later adult life. Here, we review what is currently known about the long-term consequences of perinatal and adolescent cannabinoid exposure. The most consistent findings point to long-term impairments in cognitive function that are associated with structural alterations and disturbed synaptic plasticity. In addition, several neurochemical modifications are also evident after prenatal or adolescent cannabinoid exposure, especially in the endocannabinoid, glutamatergic, dopaminergic and opioidergic systems. Important sexual dimorphisms are also evident in terms of the long-lasting effects of cannabinoid consumption during pregnancy and adolescence, and cannabinoids possibly have a protective effect in adolescents who have suffered traumatic life challenges, such as maternal separation or intense stress. Finally, we suggest some future research directions that may encourage further advances in this exciting field.

Synthetic cannabinoids: epidemiology, pharmacodynamics, and clinical implications

BACKGROUND

Synthetic cannabinoids (SC) are a heterogeneous group of compounds developed to probe the endogenous cannabinoid system or as potential therapeutics. Clandestine laboratories subsequently utilized published data to develop SC variations marketed as abusable designer drugs. In the early 2000s, SC became popular as "legal highs" under brand names such as Spice and K2, in part due to their ability to escape detection by standard cannabinoid screening tests. The majority of SC detected in herbal products have greater binding affinity to the cannabinoid CB1 receptor than does Δ(9)-tetrahydrocannabinol (THC), the primary psychoactive compound in the cannabis plant, and greater affinity at the CB1 than the CB2 receptor. In vitro and animal in vivo studies show SC pharmacological effects 2-100 times more potent than THC, including analgesic, anti-seizure, weight-loss, anti-inflammatory, and anti-cancer growth effects. SC produce physiological and psychoactive effects similar to THC, but with greater intensity, resulting in medical and psychiatric emergencies. Human adverse effects include nausea and vomiting, shortness of breath or depressed breathing, hypertension, tachycardia, chest pain, muscle twitches, acute renal failure, anxiety, agitation, psychosis, suicidal ideation, and cognitive impairment. Long-term or residual effects are unknown. Due to these public health consequences, many SC are classified as controlled substances. However, frequent structural modification by clandestine laboratories results in a stream of novel SC that may not be legally controlled or detectable by routine laboratory tests.

METHODS

We present here a comprehensive review, based on a systematic electronic literature search, of SC epidemiology and pharmacology and their clinical implications.

Neurodevelopmental performance among school age children in rural Guatemala is associated with prenatal and postnatal exposure to carbon monoxide, a marker for exposure to woodsmoke

We investigated whether early life chronic exposure to woodsmoke, using personal passive 48-h carbon monoxide (CO) as an indicator, is associated with children's neurodevelopmental and behavioral performance. CO measures were collected every 3 months from 2002 to 2005 among mother-child dyads during the Randomized Exposure Study of Pollution Indoors and Respiratory Effects (RESPIRE) stove intervention trial in San Marcos, Guatemala. From March to June, 2010, study children of age 6-7 years, performed a follow-up non-verbal, culturally adapted neurodevelopmental assessment. We found inverse associations between CO exposure of pregnant mothers during their 3rd trimesters (m=3.8ppm ± 3.0ppm; range: 0.6-12.5 ppm) and child neuropsychological performance. Scores on 4 out of 11 neuropsychological tests were significantly associated with mothers' 3rd trimester CO exposures, including visuo-spatial integration (p<0.05), short-term memory recall (p<0.05), long-term memory recall (p<0.05), and fine motor performance (p<0.01) measured using the Bender Gestalt-II's Copy, Immediate Recall, and an adapted version of a Delayed Recall Figures drawing, and the Reitan-Indiana's Finger Tapping Tests, respectively. These 4 significant finding persisted with adjustment for child sex, age, visual acuity, and household assets (socio-economic status). Summary performance scores were also significantly associated with maternal 3rd trimester CO when adjusted for these covariates. Other variables accounting for variance but were excluded in our final multiple regression models included the following: HOME environment stimulation score, child examiner, WHO height-for-age percentile, and age that the infant stopped breastfeeding. This seems to be the first study on woodsmoke exposure and neurodevelopment, and the first longitudinal birth cohort study on chronic early life CO exposures, determined by high quality measures of mothers' and infants' personal CO exposures, and using well-established, reliable child neuropsychological tests. Further research is needed to replicate our results and inform future interventions and air quality standards for woodsmoke and CO.

Neuroglobin expression in the cochlea of rat pups exposed to chronic very mild carbon monoxide (25ppm) in air during and after the prenatal period

The distribution of neuroglobin (Ngb) was investigated in the normal rat cochlea using immunohistochemistry and non-radioactive insitu hybridization. We also determined whether chronic, very mild CO exposure at 25ppm in air over the gestational and postnatal period alters the expression of Ngb. Pregnant rats were exposed chronically to CO from gestational days 5-20. Four groups were made as follows: prenatal exposure to CO only; prenatal exposure to CO followed by postnatal exposure from postnatal days (5) P5 to P20; rat pups were exposed to CO from P5 to P20; controls (air without CO). In normal adult rats and control group pups, Ngb was found in spiral ganglia neurons, fibrocytes of the spiral ligament, and supporting cells of the organ of Corti. Ngb was not present in the stria vascularis and the inner and outer hair cells. At P20 Ngb immunoreactivity and transcript expression decreased in spiral ganglia neurons and the spiral ligament in the prenatal and pre- and postnatal groups. This decrease was not observed in the postnatal group. Ngb-IR did not decrease in supporting cells in any CO group. Cytochrome-C immunoreactivity followed Ngb distribution in normal controls and CO treated groups. A decrease in Ngb in spiral ganglia neurons and rat spiral ligament, but not in supporting cells, following CO exposure supports the idea that chronic, mild exposure to CO may create a vulnerable cellular environment predisposed to adverse cochlear development.

Evidence for oxidative stress in the developing cerebellum of the rat after chronic mild carbon monoxide exposure (0.0025% in air)

BACKGROUND

The present study was designed to test the hypothesis that chronic very mild prenatal carbon monoxide (CO) exposure (25 parts per million) subverts the normal development of the rat cerebellar cortex. Studies at this chronic low CO exposure over the earliest periods of mammalian development have not been performed to date. Pregnant rats were exposed chronically to CO from gestational day E5 to E20. In the postnatal period, rat pups were grouped as follows: Group A: prenatal exposure to CO only; group B: prenatal exposure to CO then exposed to CO from postnatal day 5 (P5) to P20; group C: postnatal exposure only, from P5 to P20, and group D, controls (air without CO). At P20, immunocytochemical analyses of oxidative stress markers, and structural and functional proteins were assessed in the cerebellar cortex of the four groups. Quantitative real time PCR assays were performed for inducible (iNOS), neuronal (nNOS), and endothelial (eNOS) nitric oxide synthases.

RESULTS

Superoxide dismutase-1 (SOD1), SOD2, and hemeoxygenase-1 (HO-1) immunoreactivity increased in cells of the cerebellar cortex of CO-exposed pups. INOS and nitrotyrosine immunoreactivity also increased in blood vessels and Purkinje cells (PCs) of pups from group-A, B and C. By contrast, nNOS immunoreactivity decreased in PCs from group-B. Endothelial NOS immunoreactivity showed no changes in any CO-exposed group. The mRNA levels for iNOS were significantly up-regulated in the cerebellum of rats from group B; however, mRNA levels for nNOS and eNOS remained relatively unchanged in groups A, B and C. Ferritin-H immunoreactivity increased in group-B. Immunocytochemistry for neurofilaments (structural protein), synapsin-1 (functional protein), and glutamic acid decarboxylase (the enzyme responsible for the synthesis of the inhibitory neurotransmitter GABA), were decreased in groups A and B. Immunoreactivity for two calcium binding proteins, parvalbumin and calbindin, remained unchanged. The immunoreactivity of the astrocytic marker GFAP increased after prenatal exposure.

CONCLUSION

We conclude that exogenously supplied CO during the prenatal period promotes oxidative stress as indicated by the up-regulation of SOD-1, SOD-2, HO-1, Ferritin-H, and iNOS with increased nitrotyrosine in the rat cerebella suggesting that deleterious and protective mechanisms were activated. These changes correlate with reductions of proteins important to cerebellar function: pre-synaptic terminals proteins (synapsin-1), proteins for the maintenance of neuronal size, shape and axonal quality (neurofilaments) and protein involved in GABAergic neurotransmission (GAD). Increased GFAP immunoreactivity after prenatal CO-exposure suggests a glial mediated response to the constant presence of CO. There were differential responses to prenatal vs. postnatal CO exposure: Prenatal exposure seems to be more damaging; a feature exemplified by the persistence of markers indicating oxidative stress in pups at P20, following prenatal only CO-exposure. The continuation of this cellular environment up to day 20 after CO exposure suggests the condition is chronic. Postnatal exposure without prenatal exposure shows the least impact, whereas prenatal followed by postnatal exposure exhibits the most pronounced outcome among the groups.