The benzodiazepine receptor antagonist, flumazenil does not block clinical effects of delta-9-tetrahydrocannabinol

Fifteen normal volunteer men were given intravenous doses of 2 mg of delta-9-tetrahydrocannabinol (THC) and 3 were given doses of 0.5 mg. Five, 15 and 30 minutes later, they were given intravenous doses of the benzodiazepine receptor antagonist, flumazenil. Doses of this compound ranged between 0.1 and 3.2 mg for single doses and 0.7 and 6.4 mg for total doses, being increased progressively with each successive subject, until dose-ranging was completed in 10 subjects. After that 5 subjects were given doses of 2 mg of THC on two occasions, followed by either doses of 3.2 or 6.4 mg flumazenil or placebo, administered under blind conditions. Three subjects were treated with 0.5 mg doses of THC followed by 3.2 mg of flumazenil or placebo under similar conditions. Despite doses of the antagonist which would have been adequate to reverse the effects of substantial doses of benzodiazepines, little ameliorative action was observed on the level of intoxication or the degree of conjunctival injection, two quite reliable clinical indicators of THC action. The benzodiazepine receptor does not seem to play any significant role in the psychoactive actions and conjunctival injection produced by THC.     

delta 9-Tetrahydrocannabinol and cannabidiol: dose-dependent effects on evoked potentials in the hippocampal slice

The effects of (-) trans-delta 9-tetrahydrocannabinol (THC) and its metabolite cannabidiol (CBD) were investigated on evoked responses in the CA1 and dentate gyrus regions of the guinea pig transverse hippocampal slice. In both areas orthodromically evoked responses were enhanced by 10(-7) M THC, while 10(-6) M THC caused depression. Antidromic responses were not significantly affected. Antidromically-evoked inhibition in the CA1 region was decreased at low doses and unaffected at higher doses, while the facilitation by orthodromic interaction was unaffected at both dose ranges. The early part of the orthodromic field potential corresponding to the excitatory postsynaptic potential (EPSP) was enhanced at 10(-7) M in both areas. CBD (10(-6) M) decreased facilitation in CA1, and caused delayed excitation in the dentate granule layer. This study supports the conclusion that the biphasic effects of THC are dose dependent.     

Teratologic evaluation of synthetic delta 9-tetrahydrocannabinol in rabbits.

Synthetic delta 9-tetrahydrocannabinol (THC) was dissolved in undiluted propylene glycol and administered in daily subcutaneous doses of 15.0, 30.0 or 60.0 mg/kg to pregnant New Zealand white rabbits on days 7--19 of gestation. Maternal food consumption and weight gain were markedly reduced at all dose levels. Embryotoxicity and embryocidal effects were observed in the form of reduced litter weight and number of viable fetuses, respectively, in offspring from pregnant mothers treated with THC. However, on the basis of extensive external, visceral and skeletal examination of all fetuses it may be concluded that THC is not teratogenic in the New Zealand white strain rabbit following subcutaneous administration of doses as high as 60.0 mg/kg/day during the critical period of organogenesis (days 7--19 of gestation). On the other hand, an oral dose of thalidomide (200.0 mg/kg/day), the positive control used in this study, was both embryocidal and teratogenic.     

Effects of 9-ene-tetrahydrocannabinol on uterine estrogenicity in the mouse.

Several early (Phase I) and late (Phase II) estrogenic effects of 9-ene-tetrahydrocannabinol (THC) were examined in the adult mouse uterus. An injection of THC (2.5 or 10 mg/kg body wt) in ovariectomized mice neither stimulated uterine water imbibition or accumulation of [125I]bovine serum albumin (Phase I responses) at 6 h, nor antagonized these Phase I responses elicited by estradiol-17 beta (E2). With respect to Phase II responses, although single injections of THC (2.5, 5.0 and 10 mg/kg body wt) alone were ineffective in influencing uterine weight at 24 h or incorporation of [3H]thymidine at 18 h, this drug interfered with these responses elicited by E2 in a dose-dependent manner. In contrast, an injection of THC in progesterone (P4)-primed ovariectomized mice modestly enhanced (61%) uterine incorporation of [3H]thymidine. However, E2-stimulated uterine thymidine incorporation in P4-primed ovariectomized mice was antagonized by THC treatment. Effects of THC on blastocyst implantation were examined. Single or multiple injections of various doses of THC neither induced implantation in P4-primed delayed implanting mice, nor interfered with E2-induced implantation. Furthermore, daily injections of THC (10 mg/kg body wt) during the peri-implantation period had no apparent adverse effects on implantation, or on experimentally induced decidualization (deciduomata). The data suggest that THC is neither pro- nor antiestrogenic with respect to Phase I responses. However as regards Phase II responses, THC is modestly pro-estrogenic in the P4-treated uterus, but is anti-estrogenic in the presence of E2. These estrogen agonistic/antagonistic effects of THC on uterine Phase II responses do not adversely affect the process of implantation and decidualization.     

The effect of hypothermic doses of 1-Δ9-tetrahydrocannabinol on biogenic amine metabolism in selected parts of the rat brain

Hypothalamic and brainstem biogenic amine metabolism was investigated in rats following the administration of hypothermic doses of 1-Δ⁹-tetrahydrocannabinol (THC). The dose-dependent fall in body temperature induced by THC was both rapid in onset and prolonged in duration. The disruption in thermoregulation, however, was unaccompanied by any observed alteration in the concentration of turnover rate of 5-hydroxytryptamine (5-HT) in the brain tissues studied. Norepinephrine (NE) was also unchanged, with the exception of a reduction in the amount of brainstem NE 30 min after the administration of 50 mg/kg THC. These observations indicate that the hypothermic effect of THC is not mediated by changes in brain 5-HT or NE metabolism.     

Sex-Dependent Psychoneuroendocrine Effects of THC and MDMA in an Animal Model of Adolescent Drug Consumption

Ecstasy is a drug that is usually consumed by young people at the weekends and frequently, in combination with cannabis. In the present study we have investigated the long-term effects of administering increasing doses of delta-9-tetrahydrocannabinol [THC; 2.5, 5, 10 mg/kg; i.p.] from postnatal day (pnd) 28 to 45, alone and/or in conjunction with 3,4-methylenedioxymethamphetamine [MDMA; two daily doses of 10 mg/kg every 5 days; s.c.] from pnd 30 to 45, in both male and female Wistar rats. When tested one day after the end of the pharmacological treatment (pnd 46), MDMA administration induced a reduction in directed exploration in the holeboard test and an increase in open-arm exploration in an elevated plus maze. In the long-term, cognitive functions in the novel object test were seen to be disrupted by THC administration to female but not male rats. In the prepulse inhibition test, MDMA-treated animals showed a decrease in prepulse inhibition at the most intense prepulse studied (80 dB), whereas in combination with THC it induced a similar decrease at 75 dB. THC decreased hippocampal Arc expression in both sexes, while in the frontal cortex this reduction was only evident in females. MDMA induced a reduction in ERK1/2 immunoreactivity in the frontal cortex of male but not female animals, and THC decreased prepro-orexin mRNA levels in the hypothalamus of males, although this effect was prevented when the animals also received MDMA. The results presented indicate that adolescent exposure to THC and/or MDMA induces long-term, sex-dependent psychophysiological alterations and they reveal functional interactions between the two drugs.     

Maternal age does not affect tetrahydrocannabinol's in utero actions in rats

The potential contribution of maternal age to tetrahydrocannabinol's (THC) in utero effects in rats was studied. Pregnant animals were intubated with 25, 10 or 0 mg/kg of THC from gestation day six to parturition. Animals in the 10 and 0 mg/kg groups were pair fed to those given the 25 mg/kg dose. Each series of doses was administered to females three, four or six months of age. THC lowered maternal weight gain and weights of offspring at birth and at 21 days of age, but did not affect litter size, spontaneous alternation or passive avoidance learning in offspring. Increased maternal age was associated with smaller litter size and lower birth weight and weight at 21 days, but did not interact significantly with THC.     

The role of benzodiazepine receptors in the discriminative stimulus properties of delta-9-tetrahydrocannabinol

Twenty male Sprague-Dawley rats were trained to discriminate 3.0 mg/kg delta-9-tetrahydrocannabinol (THC) from its vehicle. Following acquisition of this discrimination animals were tested for generalization to 3.0 mg/kg diazepam. Thirteen animals showed a generalization from THC to diazepam, whereas the remaining seven animals did not. The generalization curve for diazepam was dose-dependent from 0.1 to 10.0 mg/kg in the first group; the latter group showed no generalization from THC at any dose of diazepam in this range. No differences were found between these groups in the generalization curve for THC. The benzodiazepine antagonist Ro 15-1788 (2.0 mg/kg) antagonized the generalization to diazepam in the group that discriminated diazepam as THC. In contrast, Ro 15-1788 increased THC lever responding of 10 mg/kg diazepam in the group which did not generalize from THC. Ro 15-1788 did not alter the discriminability of THC in either group. THC also showed partial generalization to pentobarbital (1 to 10 mg/kg). The generalization was again complete in one subgroup and absent in another, but there was only a 43 percent overlap between the subgroups found with testing for generalization to diazepam. The percent THC lever responding with 3.0 mg/kg pentobarbital was increased by Ro 15-1788 in the group which generalized to diazepam, but not the other group. These data suggest that the discriminative stimulus properties of THC may have some commonality with the effects of diazepam in a subpopulation of rats trained to discriminate THC. These THC-like effects of diazepam are probably mediated by benzodiazepine receptors since they are antagonized by a specific benzodiazepine receptor antagonist.     

Tetrahydrocannabinol (THC): Metabolism and subjective effects

C-14-labeled delta-9-tetrahydrocannabinol (delta-9-THC) was administered in spiked cigarettes to nine experienced marijuana smokers. Blood samples obtained by repeated venipuncture showed that the subjects' subjective estimates of being “high” appeared to parallel the blood concentration of THC metabolites at least as closely as the blood concentration of THC itself. After 30 minutes, subjective effects declined less rapidly than either THC or its metabolites.Substantial inter-individual consistency in THC concentrations was found, suggesting that administration of THC in cigarettes under standardized smoking conditions can produce reliable blood concentrations of THC.A second session was run with the same subjects, this time omitting venipuncture, and using unlabeled THC. Significant differences between the effects of initial doses of THC under stress and no-stress conditions appeared in the detailed subjective effects inventories provided by subjects.     

Suppressive effect of delta 9-tetrahydrocannabinol in vitro on phagocytosis by murine macrophages

Incubation of normal mouse peritoneal cells consisting of over 90% phagocytizing macrophages with delta 9-tetrahydrocannabinol (THC) resulted in a inhibition of phagocytic function. The THC in a dose-related manner suppressed the percentage of macrophages per culture which ingested yeast and the average number of yeast particles ingested by the phagocytizing macrophages. The vehicle used to suspend the THC in vitro, i.e., DMSO, had no detectable effect on macrophage function. Suppression of phagocytosis with no effects on viability or cell number occurred with doses of 10 micrograms or less THC per milliliter culture medium. Measurable suppression also occurred after 24- to 48-hr treatment of the macrophages with the THC. This compound had little if any detectable effect on phagocytosis when added directly to the cultures shortly before testing for phagocytosis. Further studies concerning the effects of THC on macrophage function appear warranted.     

Modulation of function of three ABC drug transporters, P-glycoprotein (ABCB1), mitoxantrone resistance protein (ABCG2) and multidrug resistance protein 1 (ABCC1) by tetrahydrocurcumin, a major metabolite of curcumin

Many studies have been performed with the aim of developing effective resistance modulators to overcome the multidrug resistance (MDR) of human cancers. Potent MDR modulators are being investigated in clinical trials. Many current studies are focused on dietary herbs due to the fact that these have been used for centuries without producing any harmful side effects. In this study, the effect of tetrahydrocurcumin (THC) on three ABC drug transporter proteins, P-glycoprotein (P-gp or ABCB1), mitoxantrone resistance protein (MXR or ABCG2) and multidrug resistance protein 1 (MRP1 or ABCC1) was investigated, to assess whether an ultimate metabolite form of curcuminoids (THC) is able to modulate MDR in cancer cells. Two different types of cell lines were used for P-gp study, human cervical carcinoma KB-3-1 (wild type) and KB-V-1 and human breast cancer MCF-7 (wild type) and MCF-7 MDR, whereas, pcDNA3.1 and pcDNA3.1-MRP1 transfected HEK 293 and MXR overexpressing MCF7AdrVp3000 or MCF7FL1000 and its parental MCF-7 were used for MRP1 and MXR study, respectively. We report here for the first time that THC is able to inhibit the function of P-gp, MXR and MRP1. The results of flow cytometry assay indicated that THC is able to inhibit the function of P-gp and thereby significantly increase the accumulation of rhodamine and calcein AM in KB-V-1 cells. The result was confirmed by the effect of THC on [³H]-vinblastine accumulation and efflux in MCF-7 and MCF-7MDR. THC significantly increased the accumulation and inhibited the efflux of [³H]-vinblastine in MCF-7 MDR in a concentration-dependent manner. This effect was not found in wild type MCF-7 cell line. The interaction of THC with the P-gp molecule was clearly indicated by ATPase assay and photoaffinity labeling of P-gp with transport substrate. THC stimulated P-gp ATPase activity and inhibited the incorporation of [¹²⁵I]-iodoarylazidoprazosin (IAAP) into P-gp in a concentration-dependent manner. The binding of [¹²⁵I]-IAAP to MXR was also inhibited by THC suggesting that THC interacted with drug binding site of the transporter. THC dose dependently inhibited the efflux of mitoxantrone and pheophorbide A from MXR expressing cells (MCF7AdrVp3000 and MCF7FL1000). Similarly with MRP1, the efflux of a fluorescent substrate calcein AM was inhibited effectively by THC thereby the accumulation of calcein was increased in MRP1-HEK 293 and not its parental pcDNA3.1-HEK 293 cells. The MDR reversing properties of THC on P-gp, MRP1, and MXR were determined by MTT assay. THC significantly increased the sensitivity of vinblastine, mitoxantrone and etoposide in drug resistance KB-V-1, MCF7AdrVp3000 and MRP1-HEK 293 cells, respectively. This effect was not found in respective drug sensitive parental cell lines. Taken together, this study clearly showed that THC inhibits the efflux function of P-gp, MXR and MRP1 and it is able to extend the MDR reversing activity of curcuminoids in vivo.     

Lack of antiemetic effects of delta9-tetrahydrocannabinol in apomorphine-induced emesis in the dog

Clinical studies have suggested that Δ⁹-tetrahydrocannabinol (THC) may be a clinically useful antiemetic. However, the ability of THC to decrease experimentally induced emesis in animals has not been extensively studied. The present study compares the antiemetic effects of THC with chlorpromazine on apomorphine-induced emesis in the dog. THC, chlorpromazine, THC vehicle, or saline was administered i.v. 30 min prior to an i.v. infusion of apomorphine; apomorphine was infused until emesis occurred. THC had no effect on the dose of apomorphine required to produce emesis, whereas chlorpromazine increased this dose approximately 75%. Moreover, THC nearly doubled the time from the first to the last occurrence of emesis relative to control values, while chlorpromazine greatly reduced this value. In addition, THC had no effect on the stimulation of pulse rate produced by apomorphine; chlorpromazine potentiated this effect, probably through indirect mechanisms. These findings demonstrate that THC is not an antagonist of the emetic agent apomorphine in the dog.     

delta 9-Tetrahydrocannabinol antagonism of the anterior pituitary response to estradiol in immature female rats.

The potential estrogenicity or antiestrogenicity of delta 9-tetrahydrocannabinol (THC), the chief psychoactive constituent of marijuana, was evaluated in immature female rats treated for 3 days with estradiol (E2; 1 microgram/kg), THC (10 mg/kg body weight), or E2 + THC. Estradiol treatment significantly increased anterior pituitary, uterine, and oviduct weights. When THC was administered with E2, it prevented the E2-induced increase in pituitary weight, but had no effect on either the uterine or oviduct weight response to E2. In the E2 treatment group, basal prolactin levels were increased and a prolactin surge occurred on the afternoon of the 26th day of age. However, E2-stimulated basal and surge levels of prolactin were significantly attenuated by concomitant THC treatment. Moreover, pituitary prolactin concentrations, which were elevated in E2-treated rats, did not differ from control values in E2 + THC-treated animals. The E2-induced decrease in dopamine turnover rates in the medial basal hypothalamus and increase in the number of anterior pituitary dopamine D2-binding sites (Bmax) were not affected by concomitant THC treatment. Thus, THC antagonizes E2 action on the anterior pituitary via yet to be elucidated mechanism(s).     

N-D-aldopentofuranosyl-N'-[p-(isoamyloxy)phenyl]-thiourea derivatives: potential anti-TB therapeutic agents

Thiocarlide (THC; N,N'-bis[p-(isoamyloxy)phenyl]-thiourea; also known as isoxyl) has been used in the past as anti-tuberculosis agent. In an effort to improve the therapeutic value of THC several N-pentofuranosyl-N'-[p-(isoamyloxy)phenyl]-thiourea derivatives were synthesized by coupling of an aniline derivative and pentofuranosyl isothiocyanates. The MIC values of the new products against M.tb indicate that this new approach to the synthesis of potential anti-TB therapeutic agents was successful.     

Impact of insecticides on the haemogram of Rhynocoris kumarii Ambrose and Livingstone (Hem., Reduviidae)

Abstract:  The haemogram of Rhynocoris kumarii Ambrose and Livingstone comprises prohaemocytes, plasmatocytes, granular haemocytes, cystocytes and oenocytoids. The impact of five insecticides, viz. monocrotophos, dimethoate, methylparathion, quinalphos and endosulfan on the total haemocyte count (THC) and differential haemocyte counts (DHC) was studied. All of the insecticides except endosulfan initially reduced both prohaemocytes and plasmatocytes, increased the granular haemocytes, altered the percentage of cystocytes and oenocytoids and increased the total haemocyte count (THC). On the contrary, endosulfan initially increased the prohaemocytes and plasmatocytes, decreased the granular haemocytes and also the THC. The highest impact on the DHC and THC was caused by methylparathion and monocrotophos and the least impact by endosulfan. Hence, endosulfan is considered as the safest insecticide followed by dimethoate and quinalphos among these five insecticides to use with R. kumarii .     

The effects of 9-ene-tetrahydrocannabinol on hormone release and immune function

We investigated effects of 9-ene-tetrahydrocannabinol (THC) on endocrine and immunological function. Seventeen male volunteers entered into a double blind, randomized study to receive oral THC (10 mg t.i.d. for 3 days and on the morning of the fourth day) or placebo, after at least 2 weeks of abstinence. Plasma prolactin, ACTH, cortisol, luteinizing hormone and testosterone were not altered during or after THC, compared with baseline concentrations. Tests of lymphocyte function showed no differences compared to baseline between THC and placebo groups. As the relatively low dosing regimen of THC (10 mg t.i.d.) resulted in no alterations, another group of 6 men were administered higher doses of THC by inhalation (18 mg/marijuana cigarette) following the same dosing regimen. No endocrine or immunological alterations were observed. When the subjects were grouped according to their history of THC use prior to admission, heavy THC users had lower prolactin concentrations than light users. No differences were observed in concentrations of other hormones or in tests of immune function.     

On the pharmacological properties of Delta9-tetrahydrocannabinol (THC)

Cannabis is one of the first plants used as medicine, and the notion that it has potentially valuable therapeutic properties is a matter of current debate. The isolation of its main constituent, Delta9-tetrahydrocannabinol (THC), and the discovery of the endocannabinoid system (cannabinoid receptors CB1 and CB2 and their endogenous ligands) made possible studies concerning the pharmacological activity of cannabinoids. This paper reviews some of the most-important findings in the field of THC pharmacology. Clinical trials, anecdotal reports, and experiments employing animal models strongly support the idea that THC and its derivatives exhibit a wide variety of therapeutic applications. However, the psychotropic effects observed in laboratory animals and the adverse reactions reported during human trials, as well as the risk of tolerance development and potential dependence, limit the application of THC in therapy. Nowadays, researchers focus on other therapeutic strategies by which the endocannabinoid system might be modulated to clinical advantage (inhibitor or activator of endocannabinoid biosynthesis, cellular uptake, or metabolism). However, emerging evidence highlights the beneficial effects of the whole cannabis extract over those observed with single components, indicating cannabis-based medicines as new perspective to revisit the pharmacology of this plant.     

Selective inhibition of the binding of 3H-(3-MeHis2) thyrotropin releasing hormone to rat amygdala membranes by some naturally occurring cannabinoids

The effect of naturally occurring cannabinoids, delta 9-tetrahydrocannabinol (THC), cannabinol (CBN) and cannabidiol (CBD), on the brain receptors for thyrotropin releasing hormone (TRH) was investigated. TRH receptors were labeled with 3H-(3-MeHis2)TRH (3H-MeTRH). 3H-MeTRH bound specifically to rat brain membranes at a single high affinity site with a Bmax value of 49.2 +/- 0.96 fmol per mg protein and a Kd value of 3.83 +/- 0.12 nM. The binding of 3H-MeTRH to whole brain membranes was inhibited when rats were injected intraperitoneally with 3 to 30 mg/kg of THC. The extent of inhibition in the binding at 10 and 30 mg/kg was similar. THC (10 mg/kg) significantly inhibited the binding of 3H-MeTRH to amygdala membranes but did not affect the binding to membranes prepared from hippocampus, septum, cortex, striatum and the rest of the brain. THC, CBN and CBD in doses of 3 to 30 mg/kg did not affect the binding of 3H-MeTRH to hypothalamic membranes. All the three cannabinoids at 30 mg/kg inhibited the binding of 3H-MeTRH to amygdala membranes. The inhibition in the binding of 3H-MeTRH by the cannabinoids was due to changes in the Kd values but the Bmax values remained unchanged. It is concluded that both psychotomimetic and nonpsychotomimetic cannabinoids inhibit the binding of 3H-MeTR to amygdala membranes selectively, which is accomplished by decreases in the affinity of the ligand to receptors, and the amygdala may be an important brain area in some of the actions of cannabinoids.     

Cannabinoid potentiation of glycine receptors contributes to cannabis-induced analgesia

Cannabinoids enhance the function of glycine receptors (GlyRs). However, little is known about the mechanisms and behavioral implication of cannabinoid-GlyR interaction. Using mutagenesis and NMR analysis, we have identified a serine at 296 in the GlyR protein critical for the potentiation of I(Gly) by Δ(9)-tetrahydrocannabinol (THC), a major psychoactive component of marijuana. The polarity of the amino acid residue at 296 and the hydroxyl groups of THC are critical for THC potentiation. Removal of the hydroxyl groups of THC results in a compound that does not affect I(Gly) when applied alone but selectively antagonizes cannabinoid-induced potentiating effect on I(Gly) and analgesic effect in a tail-flick test in mice. The cannabinoid-induced analgesia is absent in mice lacking α3GlyRs but not in those lacking CB1 and CB2 receptors. These findings reveal a new mechanism underlying cannabinoid potentiation of GlyRs, which could contribute to some of the cannabis-induced analgesic and therapeutic effects.