Biomedical subjects

Roger G Pertwee

Publications and source records attributed to Roger G Pertwee.

7 recordsLinked to original sources

PubMed2003

Pharmacophoric requirements for the cannabinoid side chain. Probing the cannabinoid receptor subsite at C1'.

Earlier work from our laboratories has provided evidence for the existence of a subsite within the CB1 and CB2 cannabinoid receptor binding domain corresponding to substituents at the benzylic side chain position of classical cannabinoids. The existence and stereochemical features of this subsite have now been probed through the synthesis of a novel series of (-)-Delta(8)-tetrahydrocannabinol analogues bearing C1'-ring substituents. Of the compounds described here, those with C1'-dithiolane (1c), C1'-dioxolane (2d), and cyclopentyl (2a) substituents exhibited the highest affinities for CB1 and CB2. We used molecular modeling approaches to better define the stereochemical limits of the putative subsite. In vitro pharmacological testing found 1c to be a potent CB1 agonist.

Animals↗

PubMed2002

Effects of delta9-THC and WIN-55,212-2 on place preference in the water maze in rats.

RATIONALE: Cannabinoids such as delta(9)-tetrahydrocannabinol (delta(9)-THC) or WIN-55,212-2 (WIN-2) have psychoactive effects on cognition. As a result, the reinforcing properties of delta(9)-THC or WIN-2 may confound learning and memory tests with false negative results. It therefore seems advisable to assess the reinforcing properties of the drugs in the same behavioural model used for learning experiments. OBJECTIVE: We therefore developed conditioned place preference protocols in the open-field water maze and tested both delta(9)-THC (2 mg/kg) and WIN-2 (1 mg/kg and 3 mg/kg). Given that previous reports on cannabinoids have revealed conflicting data and that this was a novel behavioural test, we also tested the benzodiazepine receptor agonist diazepam (2.5 mg/kg). Some methodical refinements were appropriate in order to determine the behavioural strategy implemented by the animals. METHODS: All animals were injected intraperitoneally 30 min prior to training/testing. In experiment 1, male hooded Lister rats injected with drug were repeatedly placed on the drug-related platform and subsequently tested for place preference. In experiment 2, rats were trained to swim to the drug platform on drug days and to the vehicle platform on vehicle days. A series of probe trials was introduced to delineate what had been learned. Experiment 3 studied the effect of WIN-2 on spatial learning in the water maze. RESULTS: Neither WIN-2 nor delta(9)-THC induced place preference in the water maze. When trained in the swim procedure, however, WIN-2 was neutral, but Delta(9)-THC resulted in place aversion. Conversely, diazepam consistently produced place preference in both procedures. WIN-2 (3 mg/kg), however, produced a small learning deficit in the spatial water maze task. CONCLUSION: It appears that the reinforcing properties of delta(9)-THC and WIN-2 in the doses used here are different, despite them both being agonists at cannabinoid receptors within the central nervous system. The fact that delta(9)-THC may be aversively related to a particular context has implications for previous work reporting deficits in spatial learning.

Animals↗

PubMed2002

(-)-Cannabidiol antagonizes cannabinoid receptor agonists and noradrenaline in the mouse vas deferens.

The nonpsychoactive plant cannabinoid, (-)-cannabidiol, modulates in vivo responses to Delta(9)-tetrahydrocannabinol. We have found that cannabidiol can also interact with cannabinoid CB(1) receptor agonists in the mouse vas deferens, a tissue in which prejunctional cannabinoid CB(1) receptors mediate inhibition of electrically evoked contractions by suppressing noradrenaline and/or ATP release. Cannabidiol (0.316-10 microM) attenuated the ability of (R)-(+)-[2,3-dihydro-5-methyl-3-(4-morpholinylmethyl)pyrrolo-[1,2,3-de]-1,4-benzoxazin-6-yl]-1-naphthalenylmethanone (R-(+)-WIN55212) to inhibit contractions in a concentration-related, surmountable manner with a K(B) value (120.3 nM) well below its reported cannabinoid receptor CB(1)/CB(2) K(i) values. Cannabidiol (10 microM) also antagonized (-)-cis-3-[2-hydroxy-4-(1,1-dimethylheptyl)phenyl]-trans-4-(3-hydroxypropyl)cyclohexanol (CP55940; K(B)=34 nM) and [D-Ala(2), NMePhe(4), Gly-ol]enkephalin (DAMGO; K(B)=5.6 microM) and attenuated contractile responses to noradrenaline, phenylephrine and methoxamine but not to beta, gamma-methyleneadenosine 5'-triphosphate. At 3.16-10 microM, it increased the amplitude of evoked contractions, probably by enhancing contractile neurotransmitter release. We conclude that cannabidiol antagonizes R-(+)-WIN55212 and CP55940 by acting at prejunctional sites that are unlikely to be cannabinoid CB(1) or CB(2) receptors.

Adenosine Triphosphate↗

PubMed2002

Localisation of cannabinoid CB(1) receptor immunoreactivity in the guinea pig and rat myenteric plexus.

Activation of cannabinoid CB(1) receptors inhibits gastrointestinal motility, propulsion, and transit, whereas selective antagonism of these receptors has the opposite effects, suggesting the presence of endocannabinoid tone. Supporting evidence for presynaptic CB(1) receptors on myenteric neurons has been found in vitro. In this study, selective CB(1) receptor antibodies and neuronal markers were used to identify and characterise myenteric neurons expressing cannabinoid receptors. Whole mounts of rat and guinea pig myenteric preparations were dually labelled with antibodies against the CB(1) receptor and choline acetyltransferase, neurofilament proteins, calbindin, calretinin, synapsin I, microtubule-associated protein-2, calcitonin gene-related peptide, or substance P. The pattern of CB(1) receptor labelling and the neurochemical classification of CB(1) receptor-positive cells were markedly influenced by the species and fixation procedure. Virtually all choline acetyltransferase-immunoreactive myenteric neurons expressed CB(1) receptors in ganglia from both species. Subpopulations of neurons identified with calbindin, calretinin, and microtubule-associated protein-2 did not express CB(1) receptors. A few calcitonin gene-related peptide- and substance P-positive somata coexpressed CB(1) receptor immunoreactivity but showed little colocalisation on individual fibres. There was a close association between CB(1) receptor immunoreactivity and fibres labelled for synaptic protein, suggesting a role in the modulation of transmitter release. Functional responses to cannabinoids in the presence of hexamethonium suggest further that CB(1) receptors occur on excitatory motoneurons. In conclusion, CB(1) receptors are expressed on a variety of cholinergic sensory, interneuronal, and motor neurons in myenteric ganglia.

Animals↗

PubMed2002

Synthesis and structure-activity relationships of amide and hydrazide analogues of the cannabinoid CB(1) receptor antagonist N-(piperidinyl)- 5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide (SR141716).

Analogues of the biaryl pyrazole N-(piperidinyl)-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide (SR141716; 5) were synthesized to investigate the structure-activity relationship (SAR) of the aminopiperidine region. The structural modifications include the substitution of alkyl hydrazines, amines, and hydroxyalkylamines of varying lengths for the aminopiperidinyl moiety. Proximity and steric requirements at the aminopiperidine region were probed by the synthesis of analogues that substitute alkyl hydrazines of increasing chain length and branching. The corresponding amide analogues were compared to the hydrazides to determine the effect of the second nitrogen on receptor binding affinity. The N-cyclohexyl amide 14 represents a direct methine for nitrogen substitution for 5, reducing the potential for heteroatom interaction, while the morpholino analogue 15 adds the potential for an additional heteroatom interaction. The series of hydroxyalkyl amides of increasing chain length was synthesized to investigate the existence of additional receptor hydrogen binding sites. In displacement assays using the cannabinoid agonist [(3)H](1R,3R,4R)-3-[2-hydroxy-4-(1,1-dimethylheptyl)phenyl]-4-(3-hydroxypropyl) cyclohexan-1-ol (CP 55 940; 2) or the antagonist [(3)H]5, 14 exhibited the highest CB(1) affinity. In general, increasing the length and bulk of the substituent was associated with increased receptor affinity and efficacy (as measured in a guanosine 5'-triphosphate-gamma-[(35)S] assay). However, in most instances, receptor affinity and efficacy increases were no longer observed after a certain chain length was reached. A quantitative SAR study was carried out to characterize the pharmacophoric requirements of the aminopiperidine region. This model indicates that ligands that exceed 3 A in length would have reduced potency and affinity with respect to 5 and that substituents with a positive charge density in the aminopiperidine region would be predicted to possess increased pharmacological activity.

Animals↗

PubMed2002

Cannabinoids and multiple sclerosis.

There is a growing amount of evidence to suggest that cannabis and individual cannabinoids may be effective in suppressing certain symptoms of multiple sclerosis and spinal cord injury, including spasticity and pain. Anecdotal evidence is to be found in newspaper reports and also in responses to questionnaires. Clinical evidence comes from trials, albeit with rather small numbers of patients. These trials have shown that cannabis, Delta(9)-tetrahydrocannabinol, and nabilone can produce objective and/or subjective relief from spasticity, pain, tremor, and nocturia in patients with multiple sclerosis (8 trials) or spinal cord injury (1 trial). The clinical evidence is supported by results from experiments with animal models of multiple sclerosis. Some of these experiments, performed with mice with chronic relapsing experimental allergic encephalomyelitis (CREAE), have provided strong evidence that cannabinoid-induced reductions in tremor and spasticity are mediated by cannabinoid receptors, both CB(1) and CB(2). Endocannabinoid concentrations are elevated in the brains and spinal cords of CREAE mice with spasticity, and in line with this observation, spasticity exhibited by CREAE mice can be ameliorated by inhibitors of endocannabinoid membrane transport or enzymic hydrolysis. Research is now needed to establish whether increased endocannabinoid production occurs in multiple sclerosis. Future research should also be directed at obtaining more conclusive evidence about the efficacy of cannabis or individual cannabinoids against the signs and symptoms of these disorders, at devising better modes of administration for cannabinoids and at exploring strategies that maximize separation between the sought-after therapeutic effects and the unwanted effects of these drugs.

Animals↗

PubMed2002

Pharmacological characterization of the anandamide cyclooxygenase metabolite: prostaglandin E2 ethanolamide.

Anandamide can be metabolized by cyclooxygenase-2 to produce prostaglandin E(2) (PGE(2)) ethanolamide. The purpose of this study was to investigate the pharmacology of this novel compound. Radioligand binding experiments in membranes from human embryonic kidney cells transfected with PGE(2) receptor subtypes EP(1), EP(2), EP(3), and EP(4) revealed that PGE(2) ethanolamide has pK(i) values of 5.61 +/- 0.1, 6.33 +/- 0.01, 6.70 +/- 0.13, and 6.29 +/- 0.06, respectively, compared with 8.31 +/- 0.16, 9.03 +/- 0.04, 9.34 +/- 0.06, and 9.10 +/- 0.04 for PGE(2). PGE(2) inhibits electrically evoked contractions of the guinea pig vas deferens (EP(3) receptor-mediated), with a pEC(50) value of 9.09 +/- 0.06, compared with that of 7.38 +/- 0.09 for PGE(2) ethanolamide. In the guinea pig trachea, 100 nM PGE(2) and 1 microM PGE(2) ethanolamide produced contractions of 51.8 +/- 10.6 and 38.9 +/- 5.6% (of the histamine E(max)), respectively. The EP(1) receptor antagonist SC-51089 (10 microM) prevented the contractions induced by both compounds. In the presence of 10 microM 8-chlorodibenz[b,f][1,4]oxazepine-10(11H)-carboxylic acid, 2-[1-oxo-3-(4-pyridinyl)propyl]hydrazide, monohydrochloride (SC-51089), PGE(2) caused a concentration-related relaxation of histamine-induced contractions of this tissue (EP(2) receptor-mediated), the pEC(50) value being 8.29 +/- 0.17 compared with that of 7.11 +/- 0.18 for PGE(2) ethanolamide. In the rabbit jugular vein, PGE(2) induces relaxation (EP(4) receptor-mediated) with a pEC(50) of 9.35 +/- 0.25, compared with 7.05 +/- 0.4 for PGE(2) ethanolamide. In dorsal root ganglion neurons in culture, 3 microM PGE(2) ethanolamide evoked an increase in intracellular calcium concentration in 21% of small-diameter capsaicin-sensitive neurons. We conclude that this compound is pharmacologically active, however its physiological relevance has yet to be established.

Animals↗