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.     

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.     

Perinatal delta9-tetrahydrocannabinol exposure reduces proenkephalin gene expression in the caudate-putamen of adult female rats

Perinatal delta9-tetrahydrocannabinol (delta9-THC) exposure in rats affects several behavioral responses, such as opiate self-administration behavior or pain sensitivity, that can be directly related to changes in opioidergic neurotransmission. In addition, we have recently reported that the administration of naloxone to animals perinatally exposed to delta9-THC produced withdrawal responses, that resemble those observed in opiate-dependent rats. The purpose of the present study was to examine the basal opioid activity in the brain of adult male and female rats that had been perinatally exposed to delta9-THC. To this aim, proenkephalin mRNA levels were measured, by using in situ hybridization histochemistry, in the caudate-putamen, nucleus accumbens, central amygdala and prefrontal cingulate cortex. The results showed a marked reduction in proenkephalin mRNA levels in the caudate-putamen of delta9-THC-exposed females as compared to oil-exposed females, whereas no changes were observed between delta9-THC- and oil-exposed males. There were no differences in proenkephalin mRNA levels in the nucleus accumbens, central amygdala and prefrontal cingulate cortex between males and females perinatally exposed to delta9-THC and their respective controls, although a certain trend to decrease was observed in delta9-THC-exposed females. In summary, perinatal exposure to delta9-THC exposure decreased proenkephalin gene expression in the caudate-putamen of adult rats, although this effect exhibited a marked sexual dimorphism since it was only seen in females. This result is in agreement with a previous observation from our laboratory that females, but not males, that had been perinatally exposed to delta9-THC, self-administered more morphine in adulthood. This suggests that low levels of proenkephalin mRNA may be used as a predictor of greater vulnerability to opiates.     

Changes in quality of life after intensive care: comparison with normal data

Fourteen male rats were trained to discriminate between injections of 2 mg/kg delta-9-tetrahydrocannabinol (delta 9-THC) and vehicle in a 2-lever operant drug-discrimination paradigm. Following training, substitution tests using a cumulative dosing procedure revealed that anandamide (0.5-16 mg/kg ip), the putative endogenous camabinoid receptor ligand, failed to generalize to the discriminative stimulus properties of the training dose of delta 9-THC. However, dose-dependent generalization to the delta 9-THC cue was observed following administration of both CP-55,940 (0.05-0.8 mg/kg ip), a synthetic cannabinoid, and (R)-methanandamide (0.5-8 mg/kg ip), a metabolically stable analog of anandamide. Collectively, these results demonstrate a cannabinoid-specific in vivo effect of an anandamide compound and suggest that the naturally occurring form of anandamide may be metabolized too rapidly to produce a cannabimimetic intercceptive state when administered peripherally.     

Complex pharmacology of natural cannabinoids: evidence for partial agonist activity of delta9-tetrahydrocannabinol and antagonist activity of cannabidiol on rat brain cannabinoid receptors

Delta9-tetrahydrocannabinol (delta9-THC), cannabinol and cannabidiol are three important natural cannabinoids from the Marijuana plant (Cannabis sativa). Using [35S]GTP-gamma-S binding on rat cerebellar homogenate as an index of cannabinoid receptor activation we show that: delta9-THC does not induce the maximal effect obtained by classical cannabinoid receptor agonists such as CP55940. Moreover at high concentration delta9-THC exhibits antagonist properties. Cannabinol is a weak agonist on rat cerebellar cannabinoid receptors and cannabidiol behaves as an antagonist acting in the micromolar range.     

Competitive inhibition of delta8-tetrahydrocannabinol and its active metabolites for cannabinoid receptor binding

In vitro binding characteristics of delta8-tetrahydrocannabinol (delta8-THC) and its metabolites, 11-hydroxy-delta8-THC (11-OH-delta8-THC) and 11-oxo-delta8-THC, as well as an inactive metabolite, delta8-THC-11-oic acid, as a cannabinoid receptor site from bovine cortex were examined using the specific agonist [3H]CP-55940. 11-OH-delta8-THC and 11-oxo-delta8-THC strongly inhibited the specific binding of [3H]CP-55940. The Ki values of 11-OH-delta8-THC and 11-oxo-delta8-THC for the specific binding of [3H]CP-55940 were 52 and 143 nM, respectively, whereas that of delta8-THC-11-oic acid was 917 nM. Scatchard plot analyses indicated that 11-OH-delta8-THC and 11-oxo-delta8-THC caused a significant increase in the apparent KD value without changing the apparent Bmax. These results reveal that active metabolites of delta8-THC also competitively bind to the cannabinoid receptor as agonists.     

Inhibition of naloxone-induced withdrawal in morphine dependent mice by 1-trans-delta9-tetrahydrocannabinol

The effects of various doses of 1-trans-delta9-tetrahydrocannabinol (delta9-THC) on naloxone-induced withdrawal were studied in mice rendered dependent on morphine by the pellet implantation procedure. When administered i.p., 30 min prior to naloxone, delta9-THC, inhibited the naloxone-induced withdrawal jumping response. Two other signs of morphine withdrawal (defecation and rearing behavior) were also suppressed by deltapTHC. It is suggested that delta9-THC or some of its derivatives may have potential use in narcotic detoxification.     

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.     

Evaluation of agonist-antagonist properties of nitrogen mustard and cyano derivatives of delta 8-tetrahydrocannabinol

delta 8-Tetrahydrocannabinol (delta 8-THC) is a naturally occurring cannabinoid with a characteristic pharmacological profile of in vivo effects. Previous studies have shown that modification of the structure of delta 8-THC by inclusion of a nitrogen-containing functional group alters this profile and may alkylate the cannabinoid receptor, similar to the manner in which beta-funaltrexamine (beta-FNA) alkylates the micro-opioid receptor. Two novel analogs of delta 8-THC were synthesized: a nitrogen mustard analog with a dimethylheptyl side chain (NM-delta 8-THC) and a cyano analog with a dimethylpentyl side chain (CY-delta 8-THC). Both analogs showed high affinity for brain cannabinoid receptors and when administered acutely, produced characteristic delta 9-THC-like effects in mice, including locomotor suppression, hypothermia, antinociception and catalepsy. CY-delta 8-THC shared discriminative stimulus effects with CP 55,940; for NM-delta 8-THC, these effects also occurred, but were delayed. Although both compounds attenuated the effects of delta 9-THC in the mouse behavioral tests, evaluation of potential antagonist effects of these compounds was complicated by the fact that two injections of delta 9-THC produced similar results, suggesting that acute tolerance or desensitization might account for the observations. NM-delta 8-THC, but not CY-delta 8-THC, attenuated the discriminative stimulus effects of CP 55,940 in rats several days following injection. Hence, addition of a nitrogen-containing functional group to a traditional cannabinoid structure does not eliminate agonist effects and may produce delayed attenuation of cannabinoid-induced pharmacological effects.     

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.     

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.     

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.     

A GC-MS study of three major acidic metabolites of delta 1-tetrahydrocannabinol

The major urinary metabolite of delta 1-tetrahydrocannabinol (delta 1-THC) (1), delta 1-THC-7-oic acid (2), has been extensively studied for several purposes, including testing in the workplace for drug abuse. Immunoassays in combination with more specific methods such as gas chromatography-mass spectrometry (GC-MS), are commonly used for verification of positive results in the screening. Two additional and recently synthesized acidic metabolites of 1, 4",5"-bisnor-delta 1-THC-7,3"-dioic acid (3) and 4"-hydroxy-delta 1-THC-7-oic acid (4), were studied to widen the scientific basis in the analysis. Five different derivatives were examined using GC-MS. In addition, a new deuterated internal standard for 2, [2H10]-2, was evaluated. According to our results, suitable derivatives of 2, 3, and 4, according to chromatographic properties, are the methyl ester/silyl ether (procedure a), the methyl ester/trifluoroacetate (procedure b), or the silyl ester/silyl ether (procedure c). The estimated recoveries of [2H5]-3 and [2H6]-4 using liquid-liquid extraction were 24% and 50%, respectively. The properties of [2H10]-2 as internal standard were equivalent to those of [2H9]-2 and, under the conditions used, did not appear to give rise to a significantly higher chromatographic resolution from that of 2. However, [2H10]-2 produces ions at different mass numbers, which makes it useful as a complement to the existing deuterated internal standards of 2.     

(R)-methanandamide, but not anadamide, substitutes for Δ–9-THC in a drug-discrimination procedure.

Fourteen male rats were trained to discriminate between injections of 2 mg/kg delta-9 tetrahydrocannabinol (Δ–9-THC) and vehicle in a 2-lever operant drug-discrimination paradigm. Following training, substitution tests using a cumulative dosing procedure revealed that anandamide (0.5-16 mg/kg ip), the putative endogenous cannabinoid receptor ligand, failed to generalize to the discriminative stimulus properties of the training dose of Δ–9-THC. However, dose-dependent generalization to the Δ–9-THC cue was observed following administration of both CP-55,940 (0.05-0.8 mg/kg ip), a synthetic cannabinoid, and (R)-methanandamide (0.5-8 mg/kg ip), a metabolically stable analog of anandamide. Collectively, these results demonstrate a cannabinoid-specific in vivo effect of an anandamide compound and suggest that the naturally occurring form of anandamide may be metabolized too rapidly to produce a cannabimimetic interoceptive state when administered peripherally. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

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.     

Food and water intake, meal patterns and activity of obese and lean Zucker rats following chronic and acute treatment with delta9-tetrahydrocannabinol

A series of experiments investigated the effects of delta9-THC on food and water intakes and wheel-running activity of Zucker rats. Following chronic drug treatment (15 days), food and water intakes of all rats were suppressed, but intakes and body weights of the obese rats recovered more slowly than those of lean rats. Acute effects of the drug (24 hr) were examined using techniques of meal pattern analysis and were discussed in relation to known patterns of anorectic drug action. The drug-induced anorexia was both delayed and of short duration, with no rebound eating observed for either solid or liquid diets. Both feeding rate and meal size were reduced, but meal frequency was transiently increased. The time of onset of the first meal remained unchanged. The time course of the suppression of feeding was paralleled by a suppression in running-wheel activity. These findings suggest that the drug-induced reduction in food and water intake may be the result of a decreased level of arousal.     

Anandamide- and delta9-tetrahydrocannabinol-evoked arachidonic acid mobilization and blockade by SR141716A [N-(Piperidin-1-yl)-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4 -methyl-1H-pyrazole-3-carboximide hydrochloride]

The purpose of this study was to investigate whether anandamide induces cannabimimetic responses, mainly mobilization of arachidonic acid, in primary cultures of rat brain cortical astrocytes. Confluent monolayer cultures of astrocytes, prelabeled with [3H]arachidonic acid, were incubated with anandamide or delta9-tetrahydrocannabinol (delta9-THC) in the presence or absence of thimerosal, a fatty acid acyl CoA transferase inhibitor and phenylmethylsulfonyl fluoride, an amidohydrolase inhibitor. Anandamide and delta9-THC induced a time- and concentration-dependent release of arachidonic acid in the presence, but not in the absence, of thimerosal. Anandamide- and delta9-THC-stimulated arachidonic acid release was pertussis toxin-sensitive, indicating a receptor/G-protein involvement. A novel and selective cannabinoid receptor antagonist, SR141716A [N-(piperidin-1-yl)-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4- methyl-1H-pyrazole-3-carboximide hydrochloride], blocked the arachidonic acid release, suggesting a cannabinoid receptor-mediated pathway. In astrocytes, the magnitude of anandamide-induced arachidonic acid release was equal to that released by equimolar concentrations of delta9-THC. Furthermore, direct assay of amidohydrolase activity indicated that degradation of anandamide into arachidonic acid and ethanolamine was negligible in cortical astrocytes. Our results suggest that anandamide stimulates receptor-mediated release of arachidonic acid, and the receptor may be the cannabinoid receptor. Astrocytes, containing a cannabinoid receptor and lower or negligible amidohydrolase activity, may be an important brain cell model in which to study the cannabimimetic effects of anandamide at a cellular and molecular level.     

Effect of cannabinoids on the turnover rate of acetylcholine in rat hippocampus, striatum and cortex

The effects of delta9-tetrahydrocannabinol (delta9-THC), the major psychoactive compound of marijuana, and cannabidiol (CBD), a non-psychoactive component, on the acetylcholine (ACh) concentration and the turnover rate of ACh (TRACh) have been studied in various regions of the rat brain. Neither delta9-THC doses from 0.2 to 10 mg/kg nor CBD (10 OR 20 MG/KG) alter the ACh concentration in the brain areas examined 30 min, after the intravenous injection. However, delta9-THC (doses from 0.2 to 10 mg/kg) causes a marked dose-related decrease in the TRACh in hippocampus whereas CBD is without effect in this brain region even when 20 mg/kg is given. Furthermore, high doses of delta9-THC (5 mg/kg) and CBD (20 mg/kg) that produce a significant decrease in the TRACh of striatum fail to change the TRACh in parietal cortex. The low doses of delta9-THC required to reduce hippocampal TRACh suggest that an action on these cholinergic mechanisms may play a role in the psychotomimetic activity of delta9-THC.     

Solid-state multipulse proton Nuclear Magnetic Resonance (NMR) characterization of self-assembling polymer films

Arachidonylethanolamide (anandamide), an endogenous ligand for the cannabinoid receptor, binds competitively to brain cannabinoid receptors and shares many, but not all, of the in vivo effects of delta9-tetrahydrocannabinol. In this study, the cannabinoid effects of anandamide analogs in which the anandamide molecule was altered were assessed in a drug discrimination model. Structural manipulations of the anandamide molecule included saturation of the arachidonyl moiety with fluorination (O-586), substitution for either the ethanolamide moiety (O-612 and O-595) or C2' hydroxyl (O-585), and addition of a methyl group at various positions (O-610, O-680, and O-689). Despite the low binding affinities of the non-methylated compounds (Ki values > 2000 nM), all of the analogs had previously shown cannabinoid activity in mice. In the present study, these analogs were tested in a more pharmacologically specific delta9-tetrahydrocannabinol discrimination procedure in rats. This animal model is predictive of the subjective effects of marijuana intoxication in humans. Whereas delta9-tetrahydrocannabinol and an aminoakylindole fully substituted for the training dose of 3 mg/kg delta9-tetrahydrocannabinol, anandamide and its non-methylated analogs were not cannabimimetic in this procedure. Methylation appeared to increase binding affinity (Ki values < 150 nM) and efficacy; however, the greatest substitution produced by the methylated analogs occurred only at doses that decreased overall rates of responding, suggesting that these analogs are not fully delta9-tetrahydrocannabinol-like. The rapid metabolism of anandamide and some of its analogs undoubtedly contribute to the differences between the pharmacological profiles of the anandamides and classical cannabinoids. These results support the prediction that the subjective effects of anandamide analogs that have been developed thus far would not be cannabimimetic except at high doses.     

CB1 receptor antagonist precipitates withdrawal in mice exposed to Delta9-tetrahydrocannabinol

Although tolerance to cannabinoids has been well established, the question of cannabinoid dependence had been very controversial until the discovery of a cannabinoid antagonist, SR141716A. The objective of this study was to develop and characterize a mouse model of precipitated withdrawal indicative of cannabinoid dependence. Using a dosing regimen known to produce pharmacological and behavioral tolerance, mice were treated with Delta9-tetrahydrocannabinol (Delta9-THC) twice a day for 1 wk. SR141716A administration after the last Delta9-THC injection promptly precipitated a profound withdrawal syndrome. Typical withdrawal behavior was an increase in paw tremors and head shakes that was accompanied with a decrease in normal behavior such as grooming and scratching. Of the three Delta9-THC regimens tested, daily Delta9-THC injections of 10 and 30 mg/kg produced the greatest number of paw tremors and head shakes and the least number of grooms after challenge with SR141716A. Precipitated withdrawal was apparent after 2, 3, 7 and 14 days of treatment based on an increase in paw tremors in Delta9-THC-treated mice as compared with vehicle-treated mice. These findings are consistent with SR141716A-precipitated withdrawal in rats. Moreover, these results suggest that mice are a viable model for investigating dependence to cannabinoids.