Discriminative stimulus effects of delta 9-tetrahydrocannabinol and delta 9-11-tetrahydrocannabinol in rats and rhesus monkeys

Previous reports have suggested that delta 9-11-tetrahydrocannabinol (delta 9-11-THC), an exocyclic analog of delta 9-tetrahydrocannabinol (delta 9-THC), may have weak agonist effects as well as antagonistic properties. The purpose of the present study was to examine the effects of delta 9-11-THC in substitution and antagonism tests in rats and in rhesus monkeys trained to discriminate delta 9-THC from vehicle in two-lever drug-discrimination procedures. The substitution studies showed that delta 9-11-THC generalizes from the training dose of delta 9-THC in rats and in monkeys, although it was less potent in both species. The magnitude of the potency difference was greater in monkeys than in rats. When administered immediately following injection with the training dose of delta 9-THC, delta 9-11-THC failed to block the delta 9-THC cue in rats and showed a lack of dose-responsive inhibition in monkeys. These results suggest that delta 9-11-THC is devoid of antagonistic properties in the drug discrimination paradigm.     

Pharmacokinetics of delta9-tetrahydrocannabinol in dogs

The pharmacokinetics of intravenously administered 14C-delta9-tetrahydrocannabinol and derived radiolabeled metabolites were studied in three dogs at two doses each at 0.1 or 0.5 and 2.0 mg/kg. Two dogs were biliary cannulated; total bile was collected in one and sampled in the other. The time course for the fraction of the dose per milliliter of plasma was best fit by a sum of five exponentials, and there was no dose dependency. No drug was excreted unchanged. The mean apparent volume of distribution of the central compartment referenced to total drug concentration in the plasma was 1.31 +/- 0.07 liters, approximately the plasma volume, due to the high protein binding of 97%. The mean metabolic clearance of drug in the plasma was 124 +/- 3.8 ml/min, half of the hepatic plasma flow, but was 4131 +/- 690 ml/min referenced to unbound drug concentration in the plasma, 16.5 times the hepatic plasma flow, indicating that net metabolism of both bound and unbound drug occurs. Apparent parallel production of several metabolites occurred, but the pharmacokinetics of their appearance were undoubtedly due to their sequential production during liver passage. The apparent half-life of the metabolic process was 6.9 +/- 0.3 min. The terminal half-life of delta9-tetrahydrocannabinol in the pseudo-steady state after equilibration in an apparent overall volume of distribtuion of 2170 +/- 555 liters referenced to total plasma concentration was 8.2 +/- 0.23 days, based on the consistency of all pharmacokinetic data. The best estimate of the terminal half-life, based only on the 7000 min that plasma levels could be monitored with the existing analytical sensitivity, was 1.24 days. However, this value was inconsistent with the metabolite production and excretion of 40-45% of dose in feces, 14-16.5% in urine, and 55% in bile within 5 days when 24% of the dose was unmetabolized and in the tissue at that time. These data were consistent with an enterohepatic recirculation of 10-15% of the metabolites. Intravenously administered radiolabeled metabolites were totally and rapidly eliminated in both bile and urine; 88% of the dose in 300 min with an apparent overall volume of distribution of 6 liters. These facts supported the proposition that the return of delta9-tetrahydrocannabinol from tissue was the rate-determining process of drug elimination after initial fast distribution and metabolism and was inconsistent with the capability of enzyme induction to change the terminal half-life.     

Effects of chronic exposure to delta9-tetrahydrocannabinol on cannabinoid receptor binding and mRNA levels in several rat brain regions

Previous data showed the development of tolerance to a variety of pharmacological effects of plant and synthetic cannabinoids when administered chronically. This tolerance phenomenon has been related both to enhancement of cannabinoid metabolism and, in particular, to down-regulation of brain CB1 cannabinoid receptors, although this has been only demonstrated in extrapyramidal areas. In the present study, we have tested, by using autoradiographic analysis of CB1 receptor binding combined with analysis of CB1 receptor mRNA levels in specific brain regions by Northern blot, whether the reduction in binding levels of CB1 receptors observed in extrapyramidal areas after a chronic exposure to delta9-tetrahydrocannabinol (delta9-THC), also occurs in most brain areas that contain these receptors. Results were as follows. The acute exposure to delta9-THC usually resulted in no changes in the specific binding of CB1 receptors in all brain areas studied, discarding a possible interference in binding kinetic of the pre-bound administered drug. The only exceptions were the substantia nigra pars reticulata and the cerebral cortex, which exhibited decreased specific binding after the acute treatment with delta9-THC presumably due to an effect of the pre-bound drug. The specific binding measured in animals chronically (5 days) exposed to delta9-THC decreased ranging from approximately 20 up to 60% of the specific binding measured in control animals in all brain areas. Areas studied included cerebellum (molecular layer), hippocampus (CA1, CA2, CA3, CA4 and dentate gyrus), basal ganglia (medial and lateral caudate-putamen and substantia nigra pars reticulata), limbic nuclei (nucleus accumbens, septum nucleus and basolateral amygdaloid nucleus), superficial (CxI) and deep (CxVI) layers of the cerebral cortex and others. There were only two brain regions, the globus pallidus and the entopeduncular nucleus, where the specific binding for CB receptors was unaltered after 5 days of a daily delta9-THC administration. In addition, we have analyzed the levels of CB1 receptor mRNA in specific brain regions of animals chronically exposed to delta9-THC, in order to correlate them with changes in CB1 receptor binding. Thus, we observed a significant increase in CB1 receptor mRNA levels, but only in the striatum, with no changes in the hippocampus and cerebellum. In summary, CB1 receptor binding decreases after chronic delta9-THC exposure in most of the brain regions studied, although this was not accompanied by parallel decreases in CB receptor mRNA levels. This might indicate that the primary action of delta9-THC would be on the receptor protein itself rather than on the expression of CB1 receptor gene. In this context, the increase observed in mRNA amounts for this receptor in the striatum should be interpreted as a presumably compensatory effect to the reduction in binding levels observed in striatal outflow nuclei.     

Effects of acute administration of delta9-tetrahydrocannabinol on pulmonary hemodynamics of anesthetized dogs

In an attempt to diminish the severity of the acute and late effects of irradiation to the rectum of dogs, oral prednisone was administered to 10 dogs for 1 week prior to, during, and for 1 month following a 3-week fractionated course of 60Co exposures to the pelvis. A control group of 10 dogs received irradiation alone. The dogs were observed clinically, serial rectal biopsies were done during and following the acute reaction, and the rectum was studied following sacrifice. Observations suggest that prednisone has no beneficial effect on the acute inflammatory reaction, and increases the severity of the late tissue damage.     

Tolerance to delta9-tetrahydrocannabinol in adapted and nonadapted rabbits

Two groups of New Zealand white rabbits, one which had been adapted to the testing chamber and one which had not been adapted to the testing chamber, were given delta9-tetrahydrocannabinol (delta9-THC; 0.5 mg/kg, IV) daily for 12 days. During vehicle control and on the first and last day of delta9-THC administration, electroencephalograms (EEG's) were recorded from the motor cortex and hippocampus, while standing, sprawling and behavioral activity were recorded concurrently. The results showed that tolerance to the behavioral and EEG effects of delta9-THC occurs in rabbits and that acute and chronic effects produced by delta9-THC are influenced by environmental factors.     

A comparison of delta 9-THC and anandamide induced c-fos expression in the rat forebrain

Early studies have shown mitochondrially-mediated oxidative phosphorylation is diminished in cancer cells, with glycolysis being the main source of energy production. More recent provocative reports have indicated that the mitochondria may be involved in a host of different aspects of tumorigenesis, including mutagenesis, maintenance of the malignant phenotype, and control of apoptosis. These studies have broadened the possible roles mitochondria may play in malignancy. Further studies to define the importance of mitochondria should revolve around the functional assessment of these changes in vitro and in vivo, and will be interesting for determining their significance in human cancer.     

Effects of lead on the release of glutamate neurotransmitter in rat hippocampal slices]

The authors describe their case of the extremely rare multiple metastases of cutan melanoma malignum in the upper urinary tracts as it was treated with operations. In the case of their 17-year old patient first percutan resection of the right side of the renal pelvis-wall was done then one and half months later ureteronephrectomia was carried out on the right side because of metastases in the renal pelvis and the ureter. The primary tumour had been removed from the hairy area of the head 9 months earlier in a dermatological department. The authors have met only 14 similar cases in the international literature. In Hungary no review of any similar case has been found.     

Regulation of delta opioid receptors by delta9-tetrahydrocannabinol in NG108-15 hybrid cells

In this study we employed the neuroblastoma x glioma NG 108-15 cell line as a model for investigating the effects of long-term activation of cannabinoid receptors on delta opioid receptor desensitization, down-regulation and gene expression. Exposure of NG 108-15 cells to (-)-delta9-tetrahydrocannabinol (delta9-THC) reduced opioid receptor binding, evaluated in intact cells, by approximately 40-45% in cells exposed for 24 h to 50 and 100 nM delta9-THC and by approximately 25% in cells exposed to 10 nM delta9-THC. Lower doses of delta9-THC (0.1 and 1 nM) or a shorter exposure time to the cannabinoid (6 h) were not effective. Down-regulation of 6 opioid receptors was not observed in cells exposed for 24 h to pertussis toxin (PTX) and then treated for 24 h with 100 nM delta9-THC. In cells that were exposed for 24 h to the cannabinoid, the ability of delta9-THC and of the delta opioid receptor agonist [D-Ser2, Leu5, Thr6]enkephalin to inhibit forskolin-stimulated cAMP accumulation was significantly attenuated. Prolonged exposure of NG 108-15 cells to 100 nM delta9-THC produced a significant elevation of steady-state levels of delta opioid receptor mRNA. This effect was not observed in cells pretreated with PTX. The selective cannabinoid receptor antagonist SR 141716A blocked the effects elicited by delta9-THC on delta opioid receptor desensitization, down-regulation and gene expression; thus indicating that these are mediated via activation of cannabinoid receptors. These data demonstrate the existence, in NG 108-15 cells, of a complex cross-talk between the cannabinoid and opioid receptors on prolonged exposure to delta9-THC triggered by changes in signaling through Gi and/or G0-coupled receptors.     

delta9-tetrahydrocannabinol and the hippocampus: effects on CA1 field potentials in rats

The effects of delta9-tetrahydrocannabinol (THC) on ortho- and antidromically elicited CA1 field potentials were observed in locally anesthetized rats and in anesthetized with urethane. THC augmented amplitudes of population EPSP's as well as orthodromic and antidromic population spikes from pyramidal cells in locally anesthetized animals. Latencies to peak amplitude of these response were increased. Conditioning-test shock experiments revealed taht THC also depressed recurrent inhibition probably mediated by basket cells. In animals under urethane anesthesia THC enhanced test responses, but failed to augment population response to the conditioning stimulus. It was concluded that THC enhanced postsynaptic excitatory processes but attenuated recurrent inhibition. Urethane anesthesia completely blocked the postsynaptic excitatory effect of THC but had little apparent influence on THC's disinhibitory action.     

Reduction of the behavioral effects of delta9-tetrahydrocannabinol by hyperbaric pressure

The temporal order of development of olfactory, hippocampal and thalamocortical connections has been determined by light microscopy. Scalpel lesions were made to interrupt these connections and the resulting terminal degeneration was stained by Eager's method (1970). A post-operative survival time of one to four days was used. Evidence of the development of these connections was first obtained at the following ages: Olfactory mucosa to olfactory bulb: axon fascicles by 16 days of gestation and terminals in glomeruli at birth; Olfactory bulb to prepyriform cortex at birth; Prepyriform to entorhinal cortex at 13 days after birth; Entorhinal cortex to hippocampus (the perforant path) at 9 days; Hippocampal dentate-Ammonic mossy fibres at 9 days; Hippocampal efferent projection to the septum at birth; Subicular projections to the anterior thalamus at birth and to the mammillary body at 6 days; Hippocampal commissural connections at birth; Corticothalamic and thalamocortical connections by 2 days. These results are discussed in relation to the question of how the development of brain connections is programmed.     

Hydroxypropyl-beta-cyclodextrin and its combination with hydroxypropyl-methylcellulose increases aqueous solubility of delta9-tetrahydrocannabinol

Delta9-tetrahydrocannabinol (THC) is the main psychoactive constituent of Cannabis sativa L. and its therapeutic effects are currently under intensive study. However, THC has a very low aqueous solubility (1-2 microg/mL), which restricts its use as a pharmaceutical. The present study demonstrates that THC forms a drug-cyclodextrin complex in an aqueous solution of hydroxypropyl-beta-cyclodextrin (HP-beta-CD), resulting in a thousand-fold increase in THC solubility. This improvement in solubility can be further increased by adding 0.1% hydroxypropylmethylcellulose to the HP-beta-CD solution. The present results suggest that the use of cyclodextrins might be a simple and useful method to overcome the poor water solubility of THC.     

Effects of membrane peroxidation on [3H]acetylcholine release in rat cerebral cortical synaptosomes

[3H]Acetylcholine (ACh) release, malonaldehyde formation and 45calcium-uptake were measured in rat cerebral cortical nerve terminal that were exposed to various concentrations of ferrous and ascorbate ions. At a constant molar ratio of 25:1, ferrous:ascorbate, these ions increased malonaldehyde (MA) synthesis in a concentration-dependent manner. Treatment with these ions in the same ratio also induced a dose-related inhibition of the K(+)-depolarization-induced release of newly synthesized [3H]ACh. Combined exposure to Fe2+/ascorbate also reduced calcium ionophore A23187-induced [3H]ACh release. Neither ferrous nor ascorbate ions alone altered depolarization- or ionophore-induced [3H]ACh release over this concentration range. Depolarization- and A23187-induced 45calcium uptake were not affected by peroxidation, suggesting that membrane peroxidation influenced some process in the release-process subsequent to calcium influx in a manner similar to what is observed during aging.     

Effects of intravenous general anesthetics on [3H]GABA release from rat cortical synaptosomes

BACKGROUND: Potentiation by general anesthetics of gamma-aminobutyric acid (GABA)-mediated inhibitory transmission in the central nervous system is attributed to GABA(A) receptor-mediated postsynaptic effects. However, the role of presynaptic mechanisms in general anesthetic action is not well characterized, and evidence for anesthetic effects on GABA release is controversial. The effects of several intravenous general anesthetics on [3H]GABA release from rat cerebrocortical synaptosomes (isolated nerve terminals) were investigated. METHODS: Purified synaptosomes were preloaded with [3H]GABA and superfused with buffer containing aminooxyacetic acid and nipecotic acid to inhibit GABA metabolism and reuptake, respectively. Spontaneous and elevated potassium chloride depolarization-evoked [3H]GABA release were evaluated in the superfusate in the absence or presence of various anesthetics, extracellular Ca2+, GABA receptor agonists and antagonists, and 2,4-diaminobutyric acid. RESULTS: Propofol, etomidate, pentobarbital, and alphaxalone, but not ketamine, potentiated potassium chloride-evoked [3H]GABA release (by 1.3 to 2.9 times) in a concentration-dependent manner, with median effective concentration values of 5.4 +/- 2.8 microM (mean +/- SEM), 10.1 +/- 2.1 microM, 18.8 +/- 5.8 microM, and 4.4 +/- 2.0 microM. Propofol also increased spontaneous [3H]GABA release by 1.7 times (median effective concentration = 7.1 +/- 3.4 microM). Propofol facilitation of [3H]GABA release was Ca2+ dependent and inhibited by bicuculline and picrotoxin, but was insensitive to pretreatment with 2,4-diaminobutyric acid, which depletes cytoplasmic GABA pools. CONCLUSIONS: Low concentrations of propofol, etomidate, pentobarbital, and alphaxalone facilitated [3H]GABA release from cortical nerve terminals. General anesthetics may facilitate inhibitory GABA-ergic synaptic transmission by a presynaptic mechanism in addition to their well-known postsynaptic actions.     

Immune function alterations in mice tolerant to delta9-tetrahydrocannabinol: functional and biochemical parameters

The present study examined (1) whether the neostriatum is involved in a drug-induced conditioned locomotor response and; (2) whether this structure participates in the development of behavioral sensitization. Moreover, the present study addressed the question whether the development of behavioral sensitization is necessary for the induction of conditioning. Rats received injections of either apomorphine (2 microg) or vehicle (solution of 0.1% ascorbate/saline) into the dorsal neostriatum daily for 7 days. These treatments were performed immediately prior to (apomorphine-paired group and vehicle group) or 30 min following (apomorphine-unpaired group) 10-min placement in an open field which served as the test environment. After a 3-day drug withdrawal period, the animals were given a 10-min non-drug vehicle test trial in the test environment. Three days later, a drug test with apomorphine was administered to the animals of the paired and unpaired treatment groups; the vehicle group again received an injection of vehicle. The analysis of locomotor activity in the open field (measured as the distance traversed) revealed that locomotor activity in the apomorphine-paired group was higher than in the other groups. There were no indications for behavioral sensitization to intrastriatal apomorphine, since the locomotor response in the apomorphine-paired group did not increase, but rather decreased with daily repeated injections of apomorphine. Furthermore, only the apomorphine-paired animals showed a higher locomotor response when tested after an intrastriatal injection of vehicle in the previously apomorphine-paired environment, which is indicative of a conditioned drug effect. These results suggest that the neostriatum is directly involved in the development of drug-induced conditioning of locomotor behavior but not in the establishment of behavioral sensitization.     

Inhibition of arylhydrocarbon hydroxylase induction in BALB/C mouse liver by delta9-tetrahydrocannabinol

The effects of single administration of delta9-THC on the induction of arylhydrocarbon hydroxylase activity by phenobarbital and 3-methyl cholanthrene were determined. delta9-THC completely suppressed the induction by phenobarbital and reduced the 3-methylcholanthrene induction from 455% to 177% of control. delta9-THC had no effect on phenobarbital induction when both drugs were administered daily for 2 days and mice killed on the third day. Arylhydrocarbon hydroxylase was not the only enzyme effected as delta9-THC also inhibited the induction of aminopyrine demethylase by phenobarbital. These drugs do not have any interactive effect on microsomal protein synthesis but are potent antagonists in the synthesis of nuclear RNA.     

The interaction of ethanol and delta9-tetrahydrocannabinol in man: effects on perceptual, cognitive and motor functions

Twelve paid student volunteers (8 male, 4 female) were used in a double-blind crossover experiment to investigate the effects of delta9-tetrahydrocannabinol (THC) alone, and in combination with ethanol, on human perceptual, cognitive and motor functions. Both THC (10 mg/70 kg) and ethanol (0-5 g/kg) had little effect when administered alone. The combination of drugs, however, induced a significnat decrement in performance in some of the tests and this interaction was considered to be at least additive. The peak blood ethanol concentration was higher (P = 0-05) when subjects received both ethanol and THC than when they received ethanol alone.