Maternal exposure to delta9-tetrahydrocannabinol facilitates morphine self-administration behavior and changes regional binding to central mu opioid receptors in adult offspring female rats

Opiates and cannabinoids are among the most widely consumed habit-forming drugs in humans. Several studies have demonstrated the existence of interactions between both kind of drugs in a variety of effects and experimental models. The present study has been focused to determine whether perinatal delta9-tetrahydrocannabinol (Delta9-THC) exposure affects the susceptibility to reinforcing effects of morphine in adulthood and whether these potential changes were accompanied by variations in mu opioid receptor binding in brain regions related to drug reinforcement. Adult female rats born from mothers that were daily treated with delta9-THC during gestation and lactation periods, exhibited a statistically significant increase in the rate of acquisition of intravenous morphine self-administration behavior when compared with females born from vehicle-exposed mothers, an effect that did not exist in delta9-THC-exposed male offspring. This increase was significantly greater on the last day of acquisition period. There were not significant differences when the subjects were lever pressing for food. In parallel, we have also examined the density of mu opioid receptors in the brain of adult male and female offspring that were exposed to Delta9-THC during the perinatal period. Collectively, perinatal exposure to delta9-THC produced changes in mu opioid receptor binding that differed regionally and that were mostly different as a function of sex. Thus, delta9-THC-exposed males exhibited a lower density for these receptors than their respective oil-exposed controls in the caudate-putamen area as well as in the amygdala (posteromedial cortical nucleus). On the contrary, delta9-THC-exposed females exhibited higher density of these receptors than their respective oil-exposed controls in the prefrontal cortex, the hippocampus (CA3 area), the amygdala (posteromedial cortical nucleus), the ventral tegmental area and the periaqueductal grey matter, whereas the binding was lower than control females only in the lateral amygdala. These results support the notion that perinatal delta9-THC exposure alters the susceptibility to morphine reinforcing effects in adult female offspring, in parallel with changes in mu opioid receptor binding in several brain regions.

Mesolimbic dopaminergic decline after cannabinoid withdrawal

The mesolimbic dopamine system has recently been implicated in the long-term aversive consequences of withdrawal from major drugs of abuse. In the present study we sought to determine whether mesolimbic dopamine neurons are involved in the neurobiologic mechanisms underlying withdrawal from chronic cannabinoid exposure. Rats were treated chronically with the major psychoactive ingredient of hashish and marijuana, Delta9-tetrahydrocannabinol (Delta9-THC). Administration of the cannabinoid antagonist SR 141716A precipitated an intense behavioral withdrawal syndrome, whereas abrupt Delta9-THC suspension failed to produce overt signs of abstinence. In contrast, both groups showed a reduction in dopamine cells activity as indicated by extracellular single unit recordings from antidromically identified meso-accumbens dopamine neurons. The administration of Delta9-THC to spontaneously withdrawn rats restored neuronal activity. Conversely, SR 141716A produced a further decrease of spontaneous activity in cannabinoid-treated although it was ineffective in control rats. These data indicate that withdrawal from chronic cannabinoid administration is associated with reduced dopaminergic transmission in the limbic system, similar to that observed with other addictive drugs; these changes in neuronal plasticity may play a role in drug craving and relapse into drug addiction.

Hippocampal neurotoxicity of Delta9-tetrahydrocannabinol

Marijuana consumption elicits diverse physiological and psychological effects in humans, including memory loss. Here we report that Delta9-tetrahydrocannabinol (THC), the major psychoactive component of marijuana, is toxic for hippocampal neurons. Treatment of cultured neurons or hippocampal slices with THC caused shrinkage of neuronal cell bodies and nuclei as well as genomic DNA strand breaks, hallmarks of neuronal apoptosis. Neuron death induced by THC was inhibited by nonsteroidal anti-inflammatory drugs, including indomethacin and aspirin, as well as vitamin E and other antioxidants. Furthermore, treatment of neurons with THC stimulated a significant increase in the release of arachidonic acid. We hypothesize that THC neurotoxicity is attributable to activation of the prostanoid synthesis pathway and generation of free radicals by cyclooxygenase. These data suggest that some of the memory deficits caused by cannabinoids may be caused by THC neurotoxicity.

Combined in vitro effect of marijuana and retrovirus on the activity of mouse natural killer cells

Both marijuana and retroviruses impair natural killer (NK) cell functions. No data on their simulataneous effects are available. Similarities to human AIDS induced early by Friend leukemia complex (FLC) and its replication competent helper Rowson-Parr virus (RPV) provides a mouse model to study drug-virus action. Leukemia susceptible BALB/c and resistant C57BL/6 mice were infected, then at time intervals their nylon wool-separated splenocytes were exposed to tetrahydrocannabinol (THC) for 3h. Natural killer (NK) cell activity against Yac-1 cells was assayed by 51Cr-release for 4 and 18h. Recovery of splenocytes was found to be suppressed by FLC, but in BALB/c only by RPV. After a transient enhancement in C57BL/6 by FLC, NK cell activity of both mice became suppressed early (2 to 4 days), normalized subsequently and enhanced late (11 to 14 days) postinfection. A moderate increase in BALB/c, no change in C57BL/6 were induced by low (1-2.5 microgram/ml) THC doses. NK cell activity of BALB/c became suppressed exponentially by higher (5-10 microgrtam/ ml) THC doses in 18h as compared to 4h assays, while its proportional and moderate impairment was seen in C57BL/6. The magnitude of NK cell activity of infected mice was determined by THC: enhancement or impairment followed those of untreated, infected counterparts, but on the level of THC-treated cells. Low doses hardly, high doses additively influenced NK cells of infected BALB/c. THC hardly affected very early and late enhancement in NK cell activiy of FLC infected C57BL/6, but augmented RPV induced suppression late in 18h assays. Genetic factors similar to endotoxin resistance, altered cytokine profile might determine these effects. Similar phenomena in humans might result in earlier manifestation of AIDS.

Perinatal delta(9)-tetrahydrocannabinol exposure alters the responsiveness of hypothalamic dopaminergic neurons to dopamine-acting drugs in adult rats

We have recently reported that perinatal cannabinoid exposure altered the normal development of dopaminergic neurons in the medial basal hypothalamus at early postnatal and peripubertal ages. Most of these effects tended to disappear in adulthood, although we suspect the existence of a persistent, but possibly silent, alteration in the adult activity of these neurons. To further explore this possibility, we evaluated the responsiveness of these neurons to pharmacological challenges with a variety of dopaminergic drugs administered to adult male and female rats that had been exposed to delta(9)-tetrahydrocannabinol (delta(9)-THC) or vehicle during the perinatal period. In the first experiment, we evaluated the sensitivity of hypothalamic dopaminergic neurons to amphetamine (AMPH), which causes enhancement of dopaminergic activity by a variety of mechanisms. The most interesting observation was that both adult males and females, when perinatally exposed to delta(9)-THC, showed a more marked AMPH-induced decrease in the production of L-3,4-dihydroxyphenylacetic acid (DOPAC), the main intraneuronal metabolite of dopamine (DA), although this did not affect the prolactin (PRL) release. In the second experiment, we evaluated the in vivo synthesis of DA by analyzing the magnitude of L-3,4-dihydroxyphenylalanine (L-DOPA) accumulation caused by the blockade of L-DOPA decarboxylase with NSD 1015. As expected, NSD 1015 increased L-DOPA accumulation and decreased DOPAC production, with a parallel increase in PRL release, all of similar magnitude in both delta(9)-THC- and oil-exposed adult animals. In the last experiment, we tested the magnitude of the increase in PRL release produced by the administration of either SKF 38393, a specific D1 agonist, or sulpiride, a specific D2 antagonist. Both compounds increased plasma PRL levels in adult animals of both sexes, the effects in females being significantly more marked. The perinatal exposure to delta(9)-THC also modified the degree of increase in plasma PRL levels induced by both compounds, with opposite responses as a function of sex. Thus, delta(9)-THC-exposed females responded more intensely to SKF 38393 and, particularly, to sulpiride than oil-exposed females, whereas delta(9)-THC-exposed males responded to SKF 38393 lesser than oil-exposed males, although both responded equally to sulpiride. In summary, our results are consistent with the possible existence of subtle changes in the activity of hypothalamic dopaminergic neurons in adulthood caused by the exposure to delta(9)-THC during perinatal development. These silent changes could be revealed after the administration of drugs such as: (i) AMPH, whose effect producing a decreased DOPAC accumulation was more marked in delta(9)-THC-exposed males and females; and (ii) SKF 38393 and sulpiride, whose stimulatory effects on PRL secretion were of different magnitude in delta(9)-THC-exposed animals, with an evident sexual dimorphism in the response. The neurochemical basis for these differences remains to be determined.

Psychoactive cannabinoids increase mortality and alter acute phase cytokine responses in mice sublethally infected with Legionella pneumophila

Marijuana contains both psychoactive and nonpsychoactive cannabinoids which have varying effects on the immune response system. Previous studies with delta-9-tetrahydrocannabinol (THC), the major psychoactive component of marijuana, showed that this substance augmented the susceptibility of mice to infection with the opportunistic pathogen Legionella pneumophila. The present study compared the enhancement of Legionella-induced mortality in mice due to two other major of marijuana components, cannabinol and cannabidiol, as well as the synthetic psychoactive cannabinoid CP 55,940. Inbred BALB/c mice, relatively resistant to infection with Legionella, were given the marijuana component 1 day before and 1 day after a sublethal intravenous infection with Legionella. Unlike the effect of THC, an 8 mg/kg dose of either cannabinol or cannabidiol did not affect mortality of the mice sublethally infected with Legionella. Mice given a 16 mg/kg dose of these components of marijuana, however, showed a slight to moderately increased mortality following the sublethal infection with Legionella. In contrast, a dose of 6 mg/kg of the synthetic psychoactive cannabinoid CP 55,940 given 1 day before and 1 day after infection with Legionella resulted in about 50% of the animals dying, the same level of augmentation of lethality induced by THC. Liver, spleen, and lung tissues were removed from the surviving mice 24 hr after the second THC injection and tested for the presence of viable Legionella using a standard CFU assay. The mice injected with THC before and after infection showed significantly higher levels of bacteria in their lung than mice that were not given any cannabinoid but were infected sublethally with the Legionella. Mice injected with the other cannabinoids, including the synthetic cannabinoid, showed a much smaller increase in the number of Legionella in their lung when infected with Legionella and treated with the drug. The number of bacteria recovered from the kidney and liver of the mice regardless of treatment with a cannabinoid, including with THC, did not show significant changes. RNA isolated from the spleen of the THC- and Legionella-treated animals was examined to determine at the molecular level whether acute phase pro-inflammatory cytokines (i.e., IL-1, IL-6 and TNF-alpha) were altered following drug treatment and infection, since previous studies had shown there were increased serum levels of these cytokines in the mice. It was found that the mRNA levels for IL-1 remained generally constant regardless of whether the infected animals were treated with a cannabinoid. However, the mRNA level for IL-6 was markedly increased following treatment of the infected animals with THC, suggesting the possible involvement of this pro-inflammatory cytokine in increased mortality. The mRNA level for TNF-alpha was generally low and not significantly altered in the drug treated animals. Mice given other cannabinoids, including cannabinol and cannabidiol, as well as the synthetic CP 55,940, showed no significant change in the level of mRNA for any of the cytokines tested.

Cannabis: pharmacology and toxicology in animals and humans

Cannabis is one of the most widely used drugs throughout the world. The psychoactive constituent of cannabis, delta 9-tetrahydrocannabinol (delta 9-THC), produces a myriad of pharmacological effects in animals and humans. For many decades, the mechanism of action of cannabinoids, compounds which are structurally similar to delta 9-THC, was unknown. Tremendous progress has been made recently in characterizing cannabinoid receptors both centrally and peripherally and in studying the role of second messenger systems at the cellular level. Furthermore, an endogenous ligand, anandamide, for the cannabinoid receptor has been identified. Anandamide is a fatty-acid derived compound that possesses pharmacological properties similar to delta 9-THC. The production of complex behavioral events by cannabinoids is probably mediated by specific cannabinoid receptors and interactions with other neurochemical systems. Cannabis also has great therapeutic potential and has been used for centuries for medicinal purposes. However, cannabinoid-derived drugs on the market today lack specificity and produce many unpleasant side effects, thus limiting therapeutic usefulness. The advent of highly potent analogs and a specific antagonist may make possible the development of compounds that lack undesirable side effects. The advancements in the field of cannabinoid pharmacology should facilitate our understanding of the physiological role of endogenous cannabinoids.

Perinatal delta 9-tetrahydrocannabinol exposure in rats modifies the responsiveness of midbrain dopaminergic neurons in adulthood to a variety of challenges with dopaminergic drugs

The present study has been designed to explore further the existence of a persistent, but 'silent' alteration in the adult functionality of midbrain dopaminergic neurons following perinatal cannabinoid exposure. To this end, we evaluated the responsiveness of these neurons, measured at the neurochemical or behavioral levels, to pharmacological challenges with a variety of dopaminergic drugs administered to adult male and female rats that had been exposed to delta 9-tetrahydrocannabinol (THC) or vehicle during the perinatal period. Results were as follows: In the first experiment, we tested the magnitude of motor inhibition caused by administration of dopaminergic receptor antagonists. The most interesting observation was that the administration of SCH 23390, a D1 antagonist, produced a more marked motor inhibition, reflected by a greater decrease in the ambulation measured in an open-field test, in adult animals of both sexes when they had been exposed perinatally to THC. This did not occur with the motor inhibition caused by sulpiride, a D2 antagonist. In the second experiment, we evaluated the sensitivity of midbrain dopaminergic neurons to amphetamine (AMPH), which causes, through different mechanisms, a decrease in dopamine (DA) metabolism. The most interesting observation was that adult females, when exposed perinatally to THC, exhibited a trend to lesser response to AMPH, in terms of decreasing DA metabolism, than oil-exposed females. This was observed in dopaminergic terminals reaching the limbic forebrain area, but not in those terminals reaching the striatum, and was a specific effect for THC-exposed adult females because it was not observed in THC-exposed adult males. In the third experiment, we evaluated the in vivo synthesis of DA in midbrain dopaminergic neurons by analyzing the magnitude of L-3,4-dihydroxyphenylalanine (L-DOPA) accumulation caused by the blockade of L-DOPA decarboxylase with NSD 1015. The most worthy finding was that, as occurred in the above experiment, adult females, when exposed perinatally to THC, tended to exhibit a higher ability to synthesize DA in vivo in the limbic forebrain but not in the striatum, as reflected by the increased L-DOPA accumulation observed after NSD 1015 administration. As in the above experiment, this was not seen in males. In summary, our results are consistent with the possible existence of subtle and sexually dimorphic changes in the sensitivity of midbrain dopaminergic neurons in adulthood caused by the exposure to THC during perinatal development. These silent changes could be revealed after the administration of drugs which specifically act on key processes of dopaminergic neurotransmission, such as the synthesis, reuptake and catabolism of DA and its binding to receptors.

Toxicity and carcinogenicity of delta 9-tetrahydrocannabinol in Fischer rats and B6C3F1 mice

delta 9-Tetrahydrocannabinol (delta 9-THC) was studied for potential carcinogenicity in rodents because it is the principal psychoactive ingredient in marihuana and it has potential medicinal uses. delta 9-THC in corn oil was administered by gavage to groups of male and female Fischer rats and B6C3F1 mice at 0, 5, 15, 50, 150, or 500 mg/kg, 5 days a week for 13 weeks and for 13-week plus a 9-week recovery period, and to groups of rats at 0, 12.5, or 50 mg/kg and mice at 0, 125, 250, or 500 mg/kg, 5 times a week for 2 years. In all studies, mean body weights of dosed male and female rats and mice were lower than controls but feed consumptions were similar. Convulsions and hyperactivity were observed in dosed rats and mice; the onset and frequency were dose related. Serum FSH and LH levels in all dosed male rats and corticosterone levels in 25 mg/kg female rats were significantly higher than controls at 15 months in the 2-year studies. delta 9-THC administration for 13 weeks induced testicular atrophy and uterine and ovarian hypoplasia; the lesions persisted in a 9-week recovery period. In the 2-year studies, survival of dosed rats was higher than controls; that of mice was similar to controls. Incidences of testicular interstitial cell, pancreas and pituitary gland adenomas in male rats, mammary gland fibroadenoma and uterus stromal polyp in female rats, and hepatocellular adenoma/carcinoma in male and female mice were reduced in a dose-related manner. Decreased tumor incidences may be at least in part due to reduced body weights of dosed animals. Incidences of thyroid gland follicular cell hyperplasia were increased in all dosed groups of male and female mice, and follicular cell adenomas were significantly increased in the 125 mg/kg group of males, but there was no evidence of a dose-related trend in proliferative lesions of the thyroid. There was no evidence that delta 9-THC was carcinogenic in rats or mice.

The prenatal exposure to delta 9-tetrahydrocannabinol affects the gene expression and the activity of tyrosine hydroxylase during early brain development

We have previously reported that the exposure of pregnant female rats to delta 9-tetrahydrocannabinol (THC) during the perinatal period affected the gene expression and the activity of tyrosine hydroxylase (TH) in the brain of their male offspring. Those studies were done in animals perinatally exposed to THC but tested at peripubertal and adult ages. In the present work, we explored whether these effects also appear during early fetal brain development, when TH expression plays an important role in neuronal development. To this end, TH-mRNA concentrations were measured by Northern blot analysis with a specific TH probe in the brain of fetuses at gestational days 14 and 16 which had been prenatally exposed to THC or vehicle from day 5 of gestation. In parallel, measurements of TH activity and catecholamine contents by HPLC were also done. The results obtained were as follows. The prenatal exposure to THC markedly affected the expression of the TH gene in the brain of fetuses at gestational day 14. Thus, the amounts of TH-mRNA at this age were higher (2-fold) in THC-exposed fetuses than in controls. This corresponded with a marked increase in the activity of this enzyme (3-fold) at this age. Normalization was found in both parameters at gestational day 16. In summary, the prenatal exposure to THC affected the expression of the TH gene and the activity of this enzyme in brain catecholaminergic neurons during early fetal brain development. These results support the notion that cannabinoids are able to act at the level of the gene expression of specific key proteins for brain development.

Long-term behavioral effects of perinatal exposure to delta 9-tetrahydrocannabinol in rats: possible role of pituitary-adrenal axis

This work evaluated motor behaviors in adult male and female rats exposed to delta 9-tetrahydrocannabinol (THC, 5 mg/kg) during gestation and lactation. The possibility that perinatal THC exposure induces sensitization to other drugs of abuse has also been addressed by evaluating morphine place preference conditioning (MPP) in the adult offspring. Maternal exposure to THC resulted in long-term effects on motor behaviors such as rearing, grooming and sniffing, in the adult offsprings of both sexes. Additionally, female offspring exposed to THC showed greater locomotor activity than controls, when measured using an actimeter. THC-exposed males exhibited an increased exploratory behavior in a plus-maze paradigm. When the adult animals were tested for MPP, THC-exposed offspring of both sexes exhibited an enhanced sensitivity to the rewarding effects of a moderate dose of morphine (350 micrograms/kg), an effect which was more marked in the males. These results showed that perinatal exposure to this psychoactive cannabinoid affected motor behaviors in the adult, suggesting a psychomotor activation very similar to that observed after gestational exposure to other drugs of abuse. A possible role of a THC-induced hypothalamus-pituitary-adrenal (HPA) axis activation was also evaluated in the present study. THC-exposed females exhibited higher levels of both corticotropin releasing factor (CRF-41) in the medial basal hypothalamus (MBH) and plasma corticosterone, whereas THC-exposed males showed the lower levels of both endocrine parameters. Since glucocorticoids are important modulators of both brain development, and adult brain function, these results indicate a possible role of HPA axis disturbances in the mediation of the behavioral effects described after perinatal THC exposure.

Effect of dizocilpine (MK-801) on the catalepsy induced by delta 9-tetrahydrocannabinol in mice

Mice treated with delta 9-tetrahydrocannabinol (THC; 5 and 10 mg/kg i.v.) showed the catalepsy in high bar test, and median descent latencies of catalepsy were about 150 sec. Dizocilpine (MK-801, 0.05 and 0.1 mg/kg), non-competitive N-methyl-D-aspartate (NMDA) antagonist, significantly attenuated THC-induced catalepsy. Furthermore, the anticataleptic effect of MK-801 on THC-induced catalepsy was blocked by acetylcholine agonist oxotremorine (0.005 mg/kg) and dopamine antagonist haloperidol (0.01 mg/kg), but not by NMDA. Oxotremorine, haloperidol, and NMDA themselves did not affect THC-induced catalepsy at the doses used. These results suggest that the anticataleptic effect of MK-801 on THC-induced catalepsy may be developed through dopaminergic and acetylcholinergic neuronal systems.

Delta 9-tetrahydrocannabinol injection induces cytokine-mediated mortality of mice infected with Legionella pneumophila

Delta 9-Tetrahydrocannabinol (THC) injection modulates immune cell function, but the significance of this in altering host resistance to infection is not understood. In addition, exposure to THC and other drugs of abuse during infection is associated with an acute mortality syndrome. We examined the effect of THC injection on the survival of mice infected with Legionella pneumophila (Lp). Mice given two injections of THC (8 mg/kg)-one 24 hr before and the second 24 hr after a sublethal Lp infection-experienced acute collapse and death. The drug injection after infection caused death; deaths occurred within 30 min after the injection, and neither one nor two drug injections before infection resulted in death. The THC-induced mortality resembled cytokine-mediated shock in both kinetics and symptoms; therefore, sera from drug-treated animals were measured for the acute-phase cytokines tumor necrosis factor (TNF) and interleukin 6 (IL6). The level of each cytokine was significantly elevated by THC treatment, suggesting a role in the observed mortality. To directly test this role, mice were administered a single injection of either anti-TNF alpha, anti-IL6, or a mixture of anti-IL1 alpha and -IL1 beta antibodies 1 hr before the second THC injection. Results showed that each antibody treatment protected the mice, with anti-IL6 being the most effective. Fluctuations in blood granulocytes levels also supported a role of acute-phase cytokines in THC-induced mortality. These results show that THC injection increases the blood levels of acute-phase cytokines in infected animal and that these elevated levels, at least in part, account for the mortality induced by THC injection.

Motor disturbances induced by an acute dose of delta 9-tetrahydrocannabinol: possible involvement of nigrostriatal dopaminergic alterations

Exposure to cannabinoids has been reported to affect several neurotransmitter systems and their related behaviors. The present study has been designed to further explore the effects of cannabinoids on motor behavior and test the involvement of nigrostriatal dopaminergic neurotransmission and other neurotransmitters as possible neurochemical targets for these cannabinoid effects. Male rats treated with an oral dose of delta 9-tetrahydrocannabinol (THC), the main psychoactive ingredient of cannabinoid derivatives, or vehicle were used 1 h after treatment for analyses of spontaneous motor and stereotypic activities together with neurochemical analyses of the nigrostriatal dopaminergic activity. Treatments and analyses were performed in the dark phase of photoperiod because it corresponds to the maximum behavioral expression in the rat. Neurochemical analyses were measurements of presynaptic activity--dopamine (DA) and L-3,4-dihydroxyphenylacetic acid (DOPAC) contents, tyrosine hydroxylase (TH) activity, and in vitro DA release--and postsynaptic sensitivity--number and affinity of D1 and D2 receptors--in the striatum. In addition, measurements of 5-hydroxytryptamine (5-HT) and 5-hydroxyindolacetic acid (5-HIAA) contents were also performed to evaluate serotoninergic activity in the striatum. An oral dose of THC produced a loss of spontaneous motor activity, measured in both actimeter and open-field test, and a decrease in the frequency of several stereotypic behaviors, such as rearing and self-grooming. This decrease was correlated to a low number of D1-dopaminergic receptors in the striatum, although neither DA and DOPAC contents nor TH activity and D2 receptors were altered.(ABSTRACT TRUNCATED AT 250 WORDS)

Inhibition by delta-9-tetrahydrocannabinol of tumor necrosis factor alpha production by mouse and human macrophages

Suppression by delta-9-tetrahydrocannabinol (THC) of tumor necrosis factor (TNF) production by macrophages has not been reported previously. The present study evaluated the effect in vitro of THC on soluble TNF-alpha production by cultured murine peritoneal macrophages. THC at 5 or 10 micrograms/ml added to medium [RPMI 1640 containing 10 ng LPS/ml, mouse IFN-gamma (100 u/ml), and 0.5% bovine serum albumin (BSA)] used to induce TNF significantly decreased TNF-alpha production by BALB/c mouse macrophages. Macrophages pretreated with THC at 0.1, 0.5, or 1.0 micrograms/ml in protein-free medium for 3 h at 37 degrees C, prior to TNF induction, also showed a decreased ability to produce TNF-alpha in a dose-dependent manner. Increasing the protein concentration from 0.5 to 5% BSA in the medium which was used to induce TNF prevented the inhibitory activity of THC. Human peripheral blood adherent cells treated with THC-containing medium produced less TNF-alpha than controls that were not exposed to THC. Thus, our data provide evidence that THC can inhibit TNF production by mouse and human macrophages. The drug's activity is concentration dependent and is related to the amount of serum protein in the medium used to induce this cytokine.

The human toxicity of marijuana

The pathophysiological effects of marijuana smoke and its constituent cannabinoids were reported first from in-vitro and in-vivo experimental studies. Marijuana smoke is mutagenic in the Ames test and in tissue culture and cannabinoids inhibit biosynthesis of macromolecules. In animals, marijuana or delta 9-tetrahydrocannabinol (THC), the intoxicating material it contains, produces symptoms of neurobehavioural toxicity, disrupts all phases of gonadal or reproductive function, and is fetotoxic. Smoking marijuana can lead to symptoms of airway obstruction as well as squamous metaplasia. Clinical manifestations of pathophysiology due to marijuana smoking are now being reported. These include: long-term impairment of memory in adolescents; prolonged impairment of psychomotor performance; a sixfold increase in the incidence of schizophrenia; cancer of mouth, jaw, tongue and lung in 19-30 year olds; fetotoxicity; and non-lymphoblastic leukemia in children of marijuana-smoking mothers.

Evaluation of the co-mutagenicity of ethanol and Δ9-tetrahydrocannabinol with Trenimon

The mutagenic potential of chronic treatments of male CF-1 mice with ethanol and delta 9-tetrahydrocannibinol (THC), and their comutagenic potential with a known mutagenic agent, Trenimon, were examined. This was accomplished by measuring the frequency of dominant lethal mutations arising from mating of treated males with nontreated females. Adult male mice were treated with 5% (v/v) ethanol as part of a liquid diet (28% ethanol-derived calories) for five weeks; 10 mg/kg body weight (p.o.) THC every two days for five weeks; a single injection of Trenimon (0.125 mg/kg, i.p.) on day 28 of diet treatment; and all combinations of treatments. The control group was pair-fed a liquid diet in which isocaloric sucrose replaced ethanol; these males were also given sesame oil (vehicle for THC) and saline (vehicle for Trenimon) on the same schedule as that for the treated males. Neither body weights nor hematocrits were adversely affected by any treatment. Both ethanol and Trenimon treatments resulted in a small (8-9%; p less than 0.05) decrease in testicular weight. The effect of combined treatment with ethanol and Trenimon was roughly additive. Treatment with THC had no effect on testicular weight. Seminal vesicle weights were not affected by any treatment. Treatments were without significant effect on fertility, as measured by the frequency of males producing pregnancies. Ethanol and Trenimon treatments produced approximately 3- and 7-fold increases, respectively in the frequencies of preimplantational loss over that seen for the control group (7.3%), resulting in significant ethanol and Trenimon effects (p less than 0.001). No interactive effects of ethanol and Trenimon treatments were noted. Frequencies of dead fetuses per pregnancy in the ethanol- and Trenimon-treated groups were increased approximately 2.5- and 4-fold, respectively, over the control value of approximately 16%. However, the effect of combined treatments was not greater than that due to Trenimon alone, resulting in Trenimon and ethanol effects (p less than 0.001) and ethanol-Trenimon interaction (p less than 0.001). The calculated mutation index resulting from each treatment yielded significant (p less than 0.001) ethanol- and Trenimon-induced effects. In contrast to effects of ethanol and Trenimon treatments, THC, given alone, or in combination with ethanol and/or Trenimon, had no effect on either preimplantational loss, fetal mortality or the resulting mutation index. The data suggest that chronic ethanol treatment, at levels resulting in minimal fertility impairment, increases the frequency of dominant lethal mutations. In contrast, chronic treatment with THC, as administered in the present study, appears to be without effect.(ABSTRACT TRUNCATED AT 400 WORDS)

Neurotoxicology of cannabis and THC: a review of chronic exposure studies in animals

Several laboratories have reported that chronic exposure to delta-9-tetrahydrocannabinol (THC) or marijuana extracts persistently altered the structure and function of the rat hippocampus, a paleocortical brain region involved with learning and memory processes in both rats and humans. Certain choices must be made in designing experiments to evaluate cannabis neurotoxicity, such as dose, route of administration, duration of exposure, age at onset of exposure, species of subjects, whether or how long to allow withdrawal, and which endpoints or biomarkers of neurotoxicity to measure. A review of the literature suggests that both age during exposure and duration of exposure may be critical determinants of neurotoxicity. Cannabinoid administration for at least three months (8-10% of a rat's lifespan) was required to produce neurotoxic effects in peripubertal rodents, which would be comparable to about three years exposure in rhesus monkeys and seven to ten years in humans. Studies of monkeys after up to 12 months of daily exposure have not consistently reported neurotoxicity, and the results of longer exposures have not yet been studied.

Prenatally administered delta-9-tetrahydrocannabinol temporarily inhibits the developing hypothalamo-pituitary system in rats

We have reported earlier that delta 9-tetrahydrocannabinol (THC) if injected over the 3rd week of pregnancy with a daily dose of 1 micrograms/kg b.wt., caused a significant prolongation of pregnancy and 42% of stillbirths, although no teratological effects were observed. In the present study, we investigated the postnatal development of hypothalamo-hypophyseal-gonadal axis of the above mentioned rats' living litters. The rats were killed every 5th day between the delivery (D0) and the 20th postnatal day (D20). The weight of the body and the gonads was measured and hormonal parameters were registered by RIAs. The body weight was lower in treated animals, with a higher degree in males. The weight of the gonads also decreased. Serum testosterone levels were lower in rats from D0 till D10, while at D15 and D20 no differences were recorded between controls and treated rats. No significant differences were observed in serum estrogen levels during the investigated period. Serum progesterone decreased up to D10. Pituitary luteinizing hormone (LH) diminished postpartum in both sexes up to D5. From D0 till D5, serum LH increased in males while it decreased in females. Hypothalamic luteinizing hormone releasing hormone decreased up to D15 in both sexes, less markedly in females than in males. The neuropeptide Y content of the hypothalamus was also decreased in early postnatal age. We concluded that a very low dose of prenatally administered THC caused transitory inhibition of the developing hypothalamo-pituitary-gonadal axis, i.e., postnatal changes were evoked in the neuroendocrine system. By the 20th postnatal day this effect of THC seemed to be eliminated.

Chronic marijuana smoke exposure in the rhesus monkey. IV: Neurochemical effects and comparison to acute and chronic exposure to delta-9-tetrahydrocannabinol (THC) in rats

THC is the major psychoactive constituent of marijuana and is known to produce psychopharmacological effects in humans. These studies were designed to determine whether acute or chronic exposure to marijuana smoke or THC produces in vitro or in vivo neurochemical alterations in rat or monkey brain. For the in vitro study, THC was added (1-100 nM) to membranes prepared from different regions of the rat brain and muscarinic cholinergic (MCh) receptor binding was measured. For the acute in vivo study, rats were injected IP with vehicle, 1, 3, 10, or 30 mg THC/kg and sacrificed 2 h later. For the chronic study, rats were gavaged with vehicle or 10 or 20 mg THC/kg daily, 5 days/week for 90 days and sacrificed either 24 h or 2 months later. Rhesus monkeys were exposed to the smoke of a single 2.6% THC cigarette once a day, 2 or 7 days a week for 1 year. Approximately 7 months after the last exposure, animals were sacrificed by overdose with pentobarbital for neurochemical analyses. In vitro exposure to THC produced a dose-dependent inhibition of MCh receptor binding in several brain areas. This inhibition of MCh receptor binding, however, was also observed with two other nonpsychoactive derivatives of marijuana, cannabidiol and cannabinol. In the rat in vivo study, we found no significant changes in MCh or other neurotransmitter receptor binding in hippocampus, frontal cortex or caudate nucleus after acute or chronic exposure to THC. In the monkey brain, we found no alterations in the concentration of neurotransmitters in caudate nucleus, frontal cortex, hypothalamus or brain stem.(ABSTRACT TRUNCATED AT 250 WORDS)

Prenatal delta-9-tetrahydrocannabinol in the rat: effects on auditory startle in adulthood

Either 15 or 30 mg/kg of delta-9-tetrahydrocannabinol (delta-9-THC) was administered to pregnant rats by gastric intubation from Day 2 through Day 22 of gestation. Pair-fed and nontreated groups served as controls and all treated and control litters were surrogate fostered at birth to untreated dams. When treated and control male and female offspring were tested for differences in auditory startle at 57-60 days of age, no effects were observed among any of the groups. These findings are compared with other neurobehavioral studies of adult offspring prenatally exposed to cannabis.

Animal models of opiate, cocaine, and cannabis use

A traditional concern with drugs administered during pregnancy has been teratogenicity or the production of gross structural malformations. Beginning in the 1970s, it became increasingly evident that the issue of drug safety and risk assessment went far beyond structural defects. During the 1980s, the newly emerged research specialty of "developmental toxicology" came to encompass a wide range of adverse toxic outcomes that include not only birth defects but also neurobehavioral and other functional effects as well. Substances of use and abuse--the opiates, cocaine, and cannabis--have come to exemplify a diverse group of compounds that produce a broad spectrum of developmental outcomes. Unlike alcohol, neither the use of heroin nor methadone during pregnancy is associated with an increased risk of birth defects but both produce a neonatal abstinence syndrome that can persist for as long as 6 months; follow-up to preschool years suggests possible risk of attention deficit and problems of fine motor coordination. Methodologic weaknesses of opiate animal models, especially with respect of appropriate dosing schedules, have hampered meaningful extrapolation of these studies to human risk assessment. Given the renewed interest in methadone maintenance as an important therapeutic intervention to reduce exposure to the human immunodeficiency virus, better designed animal studies are needed urgently to assess developmental risk, but these must incorporate techniques that better model human pharmacokinetics. Animal models of early cocaine exposure, driven by human reports of serious risk to the fetus and newborn, have found reproductive hazard, risk of neurobehavioral effects as well as altered CNS function. Whereas animal studies need to explore routes of administration other than sc and ig, particularly the volatilized form of cocaine, to date it appears that the processes of somatic growth and morphogenesis in rodents are not as sensitive to cocaine as is the functional development of the CNS. Finally, animal studies of cannabis have taught us some major methodologic and interpretive lessons for the continuing development and refinement of animal models of drugs of abuse. Of particular importance is that poorly controlled experiments that do not adequately consider the confounding influences of maternal toxicity, both prenatally and postnatally, are likely to yield a high rate of false-positive results. This is well illustrated by those studies of cannabis that antedated the current concern for pair-feeding and surrogate fostering. Nearly all of the studies that failed to include nutritional and fostering controls found neurobehavioral effects that included changes in activity as well as impairments in learning and memory.(ABSTRACT TRUNCATED AT 400 WORDS)

Prenatal delta-9-tetrahydrocannabinol in the rat: effects on postweaning growth

Either 15 or 30 mg/kg of delta-9-tetrahydrocannabinol (delta-9-THC) was administered from Day 2 through Day 22 of gestation. Pair-fed and nontreated groups served as controls and all treated and control litters were fostered at birth to untreated dams. When weighed at 57-60 days of age, pair-fed controls were significantly heavier than the nontreated, whereas the treated animals were intermediate between the controls. These findings are discussed with respect to nutritional studies that have reported postnatal growth enhancement following prenatal maternal undernutrition and the possibility that prenatal delta-9-THC inhibits this effect.