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Billy R Martin

Publications and source records attributed to Billy R Martin.

At least 37 records · Page 2Linked to original sources

Synthesis and pharmacological characterization of exo-2-(2'-chloro-5-pyridinyl)-7-(endo and exo)-aminobicyclo[2.2.1]heptanes as novel epibatidine analogues.

Procedures were developed for the synthesis of exo-(2'-chloro-5-pyridinyl)-7-(endo and exo)-amino[2.2.1]heptanes (3a and 3b). The compounds were evaluated for binding to the alpha4beta2 and alpha7 nicotinic acetylcholine receptors (nAChRs), for pharmacological activity in the mouse tail-flick and hot-plate assays, and for hypothermia and locomotor activity. Compounds 3a and 3b possessed alpha4beta2 nAChR binding properties similar to those of (-)-nicotine and were nAChR agonists in all four mouse assays.

Analgesics↗

Influence of the degree of unsaturation of the acyl side chain upon the interaction of analogues of 1-arachidonoylglycerol with monoacylglycerol lipase and fatty acid amide hydrolase.

Little is known as to the structural requirements of the acyl side chain for interaction of acylglycerols with monoacylglycerol lipase (MAGL), the enzyme chiefly responsible for the metabolism of the endocannabinoid 2-arachidonoylglycerol (2-AG) in the brain. In the present study, a series of twelve analogues of 1-AG (the more stable regioisomer of 2-AG) were investigated with respect to their ability to inhibit the metabolism of 2-oleoylglycerol by cytosolic and membrane-bound MAGL. In addition, the ability of the compounds to inhibit the hydrolysis of anandamide by fatty acid amide hydrolase (FAAH) was investigated. For cytosolic MAGL, compounds with 20 carbon atoms in the acyl chain and 2-5 unsaturated bonds inhibited the hydrolysis of 2-oleoylglycerol with similar potencies (IC50 values in the range 5.1-8.2 microM), whereas the two compounds with a single unsaturated bond were less potent (IC50 values 19 and 21 microM). The fully saturated analogue 1-monoarachidin did not inhibit the enzyme, whereas the lower side chain analogues 1-monopalmitin and 1-monomyristin inhibited the enzyme with IC50 values of 12 and 32 microM, respectively. The 22-carbon chain analogue of 1-AG was also potent (IC50 value 4.5 microM). Introduction of an alpha-methyl group for the C20:4, C20:3, and C22:4 compounds did not affect potency in a consistent manner. For the FAAH and the membrane-bound MAGL, there was no obvious relationship between the degree of unsaturation of the acyl side chain and the ability to inhibit the enzymes. It is concluded that increasing the number of unsaturated bonds on the acyl side chain of 1-AG from 1 to 5 has little effect on the affinity of acylglycerols for cytosolic MAGL.

Amidohydrolases↗

In vivo characterization of a novel inhibitor of CNS nicotinic receptors.

There are multiple types of nicotine acetylcholine receptors (nAChR) in the brain associated with synaptic function, signal processing, or cell survival. The therapeutic targeting of nicotinic receptors in the brain will benefit from the identification of drugs, which may be selective for their ability to activate or inhibit a limited range of these receptor subtypes. We previously identified a family of bis-tetramethylpiperidine compounds as selective inhibitors of neuronal-type nicotinic receptors. In the present study we describe the in vivo effects and properties of 2,2,6,6-tetramethylpiperidin-4-yl heptanoate (TMPH), a novel inhibitor of neuronal nicotinic receptors. Delivered systemically, this drug can block central nervous system effects of nicotine, indicating that this drug is able to cross the blood-brain barrier and access sites in the brain. Unlike the prototype CNS-active nicotinic inhibitor, mecamylamine, TMPH blocked some but not all of the CNS effects of nicotine, indicating that it has a unique selectivity for specific receptor subtypes in the brain. The nAChR subtypes that mediate the locomotor effects and hypothermic effects of nicotine appear to be less sensitive to TMPH than those which mediate analgetic effects and discriminative stimuli. These results indicate that TMPH may possess unique selectivity for specific nicotinic receptor subtypes.

Analgesics↗

1-Pentyl-3-phenylacetylindoles, a new class of cannabimimetic indoles.

A new class of cannabimimetic indoles, with 3-phenylacetyl or substituted 3-phenylacetyl substituents, has been prepared and their affinities for the cannabinoid CB1 and CB2 receptors have been determined. In general those compounds with a 2-substituted phenylacetyl group have good affinity for both receptors. The 4-substituted analogs have little affinity for either receptor, while the 3-substituted compounds are intermediate in their affinities. Two of these compounds, 1-pentyl-3-(2-methylphenylacetyl)indole (JWH-251) and 1-pentyl-3-(3-methoxyphenylacetyl)indole (JWH-302), have 5-fold selectivity for the CB1 receptor with modest affinity for the CB2 receptor. GTPgammaS determinations indicate that both compounds are highly efficacious agonists at the CB1 receptor and partial agonists at the CB2 receptor.

Acetylation↗

Enantioselective synthesis of 1-methoxy- and 1-deoxy-2'-methyl-delta8-tetrahydrocannabinols: new selective ligands for the CB2 receptor.

Two new series of cannabinoids were prepared and their affinities for the CB1 and CB2 receptors were determined. These series are the (2'R)- and (2'S)-1-methoxy- and 1-deoxy-3-(2'-methylalkyl)-delta8-tetrahydrocannabinols, with alkyl side chains of three to seven carbon atoms. These compounds were prepared by a route that employed the enantioselective synthesis of the resorcinol precursors to the cannabinoid ring system. All of these compounds have greater affinity for the CB2 receptor than the CB1 receptor and four of them, (2'R)-1-methoxy-3-(2'-methylbutyl)-delta8-THC (JWH-359), (2'S)-1-deoxy-3-(2'-methylbutyl)-delta8-THC (JWH-352), (2'S)-1-deoxy-3-(2'-methylpentyl)-delta8-THC (JWH-255), and (2'R)-1-deoxy-3-(2'-methylpentyl)-delta8-THC (JWH-255), have good affinity (K(i) = 13-47 nM) for the CB2 receptor and little affinity (K(i) = 1493 to >10,000 nM) for the CB1 receptor. In the 1-deoxy-3-(2'-methylalkyl)-delta8-THC series, the 2'S-methyl compounds in general have greater affinity for the CB2 receptor than the corresponding 2'R isomers.

Dronabinol↗

Role of lipids and lipid signaling in the development of cannabinoid tolerance.

Cannabinoid agonists such as Delta9-tetrahydrocannabinol (THC) produce a wide range of pharmacological effects both in the central nervous system and in the periphery. One of the most striking features of cannabinoids such as THC is the magnitude to tolerance that can be produced upon repetitive administration of this substance to animals. Relatively modest dosing regimens are capable of producing significant tolerance, whereas greater than 100-fold tolerance can be obtained with aggressive treatments. While cannabinoid tolerance has been studied quite extensively to establish its relevance to the health consequences of marijuana use, it has also proven to be a valuable strategy in understanding the mechanism of action of cannabinoids. The discovery of the endocannabinoid system that contains two receptor subtypes, CB1 and CB2, associated signaling pathways, endocannabinoids (anandamide and 2-arachidonoylglycerol) and their synthetic and degradative pathways has provided a means of systematically evaluating the mechanism of cannabinoid tolerance. It is well known that the CB1 cannabinoid receptor is down-regulated in states of cannabinoid tolerance along with uncoupling from its second messenger systems. Endocannabinoid levels are also altered in selected brain regions during the development of tolerance. While it is reasonable to speculate that a likely relationship exists between receptor and endocannabinoid levels, at present, little is known regarding the biological signal that leads to alterations in endocannabinoid levels. It is also unknown to what degree synthetic and degradative pathways for the endocannabinoids are altered in states of tolerance. The discovery that the brain is abundant in fatty acid amides and glycerols raises the question as to what roles these lipids contribute to the endocannabinoid system. Some of these lipids also utilize the endocannabinoid metabolic pathways, produce similar pharmacological effects, and are capable of modulating the actions of anandamide and 2-arachidonoylglycerol. In addition, there are dopamine, glycine, and serotonin conjugates of arachidonic acid that may also contribute to the actions of endocannabinoids. A systematic examination of these lipids in cannabinoid tolerance might shed light on their physiological relevance to the endocannabinoid system.

Cannabinoid Receptor Modulators↗

Nicotine physical dependence in the mouse: involvement of the alpha7 nicotinic receptor subtype.

Although chronic nicotine produces dependence in mice, the role of specific nicotinic receptors has not been examined in knockout animals. The present study utilized alpha7 nicotinic receptor knockout mice to explore the role of this receptor subunit in nicotine dependence. Mice were chronically exposed to nicotine (0 or 200 microg/ml) in their drinking water and assayed for somatic withdrawal signs, hyperalgesia (tail-flick and hot-plate) and spontaneous activity following nicotine cessation. Nicotine withdrawal produced increased somatic signs in both strains and hyperalgesia in wild-type, but not in knockout animals. These results indicate that the alpha7 nicotinic receptor subunit may mediate some aspects of nicotine dependence.

Animals↗

Synthesis, nicotinic acetylcholine receptor binding, and antinociceptive properties of 3'-substituted deschloroepibatidine analogues. Novel nicotinic antagonists.

A series of 3'-substituted deschloroepibatidine analogues (3a-g and 4) showed high affinity for alpha4beta2 binding and relatively weak affinity for alpha7 nAChRs. The 3'-ethynyl (3g) and 3'-fluoro (3a) analogues with K(i) values of 0.02 and 0.037 nM, respectively, were the most potent. Even though the alpha4beta2 binding affinity of several of the analogues were equal to that of epibatidine, all of the compounds were weak agonists in the antinociceptive, hypothermia, and spontaneous activity test in mice. In contrast, all of the compounds were functional antagonists of nicotine-induced antinociception. In general, compounds 3a-g and 4 were more potent in the tail-flick assay than the hot-plate test. For example, the 3'-fluoro analogue 3a and the N-methyl-3'-iodo analogue 4 showed AD(50) values of 0.07 and 0.04 microg/kg, respectively, in the tail flick test and only 35 and 0% inhibition at 20 and 10 microg/kg in the hot-plate assay, respectively. These results suggest that these compounds will be highly useful for identifying which specific receptor subtypes are involved in each of nicotine's pharmacological effects. The high affinity of the N-methyl-3'-iodo analogue 4 combined with its weak agonist and potent antagonist activity suggests that carbon-11 and iodine-123 analogues may be useful as PET and SPECT ligands, respectively, for studying nAChRs in vivo.

Analgesics↗

Structure-activity relationships for 1-alkyl-3-(1-naphthoyl)indoles at the cannabinoid CB(1) and CB(2) receptors: steric and electronic effects of naphthoyl substituents. New highly selective CB(2) receptor agonists.

In an effort to improve indole-based CB(2) cannabinoid receptor ligands and also to develop SAR for both the CB(1) and CB(2) receptors, 47 indole derivatives were prepared and their CB(1) and CB(2) receptor affinities were determined. The indole derivatives include 1-propyl- and 1-pentyl-3-(1-naphthoyl)indoles both with and without a 2-methyl substituent. Naphthoyl substituents include 4- and 7-alkyl groups as well as 2-, 4-, 6-, 7-methoxy and 4-ethoxy groups. The effects of these substituents on receptor affinities are discussed and structure-activity relationships are presented. In the course of this work three new highly selective CB(2) receptor agonists were identified, 1-propyl-3-(4-methyl-1-naphthoylindole (JWH-120), 1-propyl-2-methyl-3-(6-methoxy-1-naphthoylindole (JWH-151), and 1-pentyl-3-(2-methoxy-1-naphthoylindole (JWH-267). GTPgammaS assays indicated that JWH-151 is a full agonist at CB(2), while JWH-120 and JWH-267 are partial agonists. Molecular modeling and receptor docking studies were carried out on a set of 3-(4-propyl-1-naphthoyl)indoles, a set of 3-(6-methoxy-1-naphthoyl)indoles and the pair of N-pentyl-3-(2-methoxy-1-naphthoyl)indoles. Docking studies indicated that the CB(1) receptor affinities of these compounds were consistent with their aromatic stacking interactions in the aromatic microdomain of the CB(1) receptor.

Alkylation↗

CB1 cannabinoid receptor-mediated modulation of food intake in mice.

1 Marijuana's appetite-increasing effects have long been known. Recent research suggests that the CB(1) cannabinoid receptor antagonist SR141716A may suppress appetite. This study represents a further, systematic investigation of the role of CB(1) cannabinoid receptors in the pharmacological effects of cannabinoids on food intake. 2 Mice were food-restricted for 24 h and then allowed access to their regular rodent chow for 1 h. Whereas the CB(1) antagonist SR141716A dose-dependently decreased food consumption at doses that did not affect motor activity, Delta(9)-tetrahydrocannabinol (Delta(9)-THC) increased food consumption at doses that had no effect on motor activity. O-3259 and O-3257, structural analogs of SR141716A, produced effects similar to those of the parent compound. 3 Amphetamine (a known anorectic) and diazepam (a benzodiazepine and CNS depressant) decreased food consumption, but only at doses that also increased or decreased motor activity, respectively. The CB(2) cannabinoid receptor antagonist SR144528 and the nonpsychoactive cannabinoid cannabidiol did not affect food intake nor activity. 4 SR141716A decreased feeding in wild-type mice, but lacked pharmacological activity in CB(1) knockout mice; however, basal food intake was lower in CB(1) knockout mice. Amphetamine decreased feeding in both mouse genotypes. 5 These results suggest that SR141716A may affect the actions of endogenous cannabinoids in regulating appetite or that it may have effects of its own aside from antagonism of cannabinoid effects (e.g., decreased feeding behavior and locomotor stimulation). In either case, these results strongly suggest that CB(1) receptors may play a role in regulation of feeding behavior.

Animals↗

Outcomes of allogenic acellular matrix therapy in treatment of diabetic foot wounds: an initial experience.

The purpose of this study was to evaluate outcomes of persons with UT grade 2A neuropathic diabetic foot wounds treated with an acellular matrix. Data were abstracted for 17 consecutive patients with diabetes--76.5% males, aged 61.5 +/- 8.5 years with a mean glycated haemoglobin of 9.2 +/- 2.2% presenting for care at a large, multidisciplinary wound care centre. All patients received surgical debridement for their diabetic foot wounds and were placed on therapy consisting of a single application of an acellular matrix graft (GraftJacket; Wright Medical Technologies, Arlington, TN, USA) with dressing changes taking place weekly. Outcomes evaluated included time to complete wound closure and proportion of patients achieving wound closure in 20 weeks. Acellular matrix therapy was used as initial therapy and was sutured or stapled in place under a silicone-based non adherent dressing. Therapy was then followed by a moisture-retentive dressing until complete epithelialisation. In total, 82.4% of wounds measuring a mean 4.6 +/- 3.2 cm(2) healed in the 20-week evaluation period. For those that healed in this period, healing took place in a mean 8.9 +/- 2.7 weeks. We conclude that a regimen consisting of moist wound healing using an acellular matrix dressing may be a useful adjunct to appropriate diabetic foot ulcer care for deep, non-infected, non-ischaemic wounds. We await the completion of further trials in this area to confirm or refute this initial assessment.

Aged↗

Intrathecal CART (55-102) enhances the spinal analgesic actions of morphine in mice.

Cocaine- and amphetamine-regulated transcript (CART) peptides are found in brain and spinal cord areas involved in pain transmission. In the present study, we investigated the role of rat CART (55-102) in the modulation of an acute pain model after intrathecal administration. The results show that CART (55-102) was without effect on the tail-flick test after i.t. injection in mice. Interestingly, i.t. administration of CART (55-102) significantly enhanced the antinociceptive effect of morphine in the tail-flick test. These results suggest that CART (55-102) potentiates the effects of opioids to inhibit the nociceptive information transmission.

Animals↗

Inhibition of monoacylglycerol lipase and fatty acid amide hydrolase by analogues of 2-arachidonoylglycerol.

The pharmacology of monoacylglycerol lipase (MAGL) is not well understood. In consequence, the abilities of a series of analogues of 2-arachidonoylglycerol (2-AG) to inhibit cytosolic 2-oleoylglycerol and membrane-bound anandamide hydolysis by MAGL and fatty acid amide hydrolase (FAAH), respectively, have been investigated. 2-AG and its 1-regioisomer (1-AG) interacted with MAGL with similar affinities (IC(50) values 13 and 17 mum, respectively). Shorter homologues of 2-AG (2-linoleoylglycerol and 2-oleoylglycerol) had affinities for MAGL similar to 2-AG. This pattern was also seen when the arachidonoyl side chain of arachidonoyl trifluoromethylketone was replaced by an oleoyl side chain. Arachidonoyl serinol (IC(50) value 73 microM) was a weaker inhibitor of MAGL than 2-AG. The IC(50) values of noladin ether towards MAGL and FAAH were 36 and 3 microM, respectively. Arachidonoyl glycine interacted with FAAH (IC(50) value 4.9 microM) but only weakly interacted with MAGL (IC(50) value >100 microM). alpha-Methyl-1-AG had similar potencies towards MAGL and FAAH (IC(50) values of 11 and 33 microM, respectively). O-2203 (1-(20-cyano-16,16-dimethyl-eicosa-5,8,11,14-tetraenoyl) glycerol) and O-2204 (2-(20-hydroxy-16,16-dimethyl-eicosa-5,8,11,14-tetraenoyl) glycerol) were slightly less potent, but again affected both enzymes equally. alpha-Methyl-1-AG, O-2203 and O-2204 interacted only weakly with cannabinoid CB(1) receptors expressed in CHO cells (K(i) values 1.8, 3.7 and 3.2 microM, respectively, compared with 0.24 microM for 1-AG) and showed no evidence of central cannabinoid receptor activation in vivo at doses up to 30 mg kg(-1) i.v. It is concluded that compounds like alpha-Methyl-1-AG, O-2203 and O-2204 may be useful as leads for the discovery of selective MAGL inhibitors that lack direct effects upon cannabinoid receptors.

Amidohydrolases↗

Nicotine physical dependence and tolerance in the mouse following chronic oral administration.

RATIONALE: Although nicotine dependence and tolerance develop in rats, few studies have examined these processes in the mouse. Establishing such mouse models would eventually allow for an examination of the role of specific nicotinic receptor subtypes in mediating these processes (i.e. through the use of receptor knockouts). OBJECTIVES: The goals of the present study were to establish mouse models of nicotine dependence and tolerance. METHODS: Mice were chronically exposed to nicotine (0-200 mug/ml) in their drinking solution and assayed for plasma nicotine and cotinine levels, withdrawal signs following nicotine cessation (spontaneous withdrawal) or nicotinic antagonist administration (precipitated withdrawal), or nicotine tolerance. Dependence assays included somatic sign observations (paw tremors, backing and head shakes), tail-flick, plantar stimulation, elevated plus-maze and spontaneous activity. Tolerance was assayed using tail-flick, hot-plate and body temperature tests. RESULTS: Plasma nicotine and cotinine levels were elevated during oral nicotine exposure (15.85 ng/ml and 538.00 ng/ml, respectively) and quickly declined following nicotine cessation (<1 ng/ml and <2 ng/ml, respectively), providing evidence that the oral route was pharmacologically relevant. Nicotine withdrawal increased numbers of somatic signs (spontaneous and mecamylamine-precipitated withdrawal) and/or hyperalgesia (spontaneous withdrawal only). Chronic nicotine exposure also produced tolerance, as indicated by reduced responsivity to acute nicotine in assays of analgesia and hypothermia. CONCLUSIONS: These results indicate that chronic oral nicotine produces dependence and tolerance in the mouse. Further, nicotine dependence may be mediated by multiple nicotinic receptor subtypes, since specific nicotinic receptor antagonists failed to precipitate withdrawal.

Administration, Oral↗

Synthesis, nicotinic acetylcholine receptor binding, and antinociceptive properties of 2'-fluoro-3'-(substituted phenyl)deschloroepibatidine analogues. Novel nicotinic antagonist.

A series of 2'-fluoro-3'-(substituted phenyl)deschloroepibatidine analogues (5a-k) showed high affinity for alpha4beta2 binding with no affinity at alpha7 nAChRs. The most potent compound was 2'-fluoro-3'-(4-nitrophenyl)deschloroepibatidine (5g) which possessed a Ki value of 0.009 nM. Surprisingly, none of the compounds showed agonist effects in pain tests and body temperature changes in mice even when tested at 10-15 mg/kg with the exception of 5b, which showed only very weak agonist effects. In contrast, all the compounds were potent functional antagonists of nicotine-induced antinociception. Interestingly, the 3'-substituted phenyl analogues 5b-k were 10-870-fold more effective as antagonists in the tail-flick test versus the hot-plate procedure. They failed to antagonize nicotine-induced hypothermia. The 4-chlorophenyl analogue (5e) (AD50 = 0.0003 in the tail-flick test) was the most potent and selective analogue. These results suggest that these compounds will be highly useful for identifying which specific receptor subtypes are involved in each of nicotine's pharmacological effects. These compounds also deserve consideration as potential pharmacotherapies for treatment of smoking cessation.

Analgesics↗

Reversal of delta 9-tetrahydrocannabinol-induced tolerance by specific kinase inhibitors.

Tolerance develops to the pharmacological effects of Delta9-tetrahydrocannabinoid (THC) following repetitive administration. Adaptations in signaling pathways involved in tolerance to THC-induced behaviors are not understood. The objective of our study was the evaluation of kinase involvement in the expression of tolerance to the above four THC-induced behaviors. Kinase inhibitors that specifically inhibit cyclic AMP-dependent protein kinase (PKA), cyclic GMP-dependent protein kinase (PKG), calmodulin-dependent protein kinase (PKC) and src tyrosine kinase were tested for reversal of tolerance to THC's effects. PKG and PKC inhibitors did not reverse tolerance in any behavioral measure. Src tyrosine kinase inhibition reversed tolerance to only the hypoactive effects of THC. PKA inhibition reversed tolerance to all measures, although the doses of inhibitor and time-course of inhibition varied among behaviors. Thus, our data suggest that PKA activity plays a major role in THC-induced tolerance, and that THC produces its multiple effects through different signaling pathways.

Animals↗

Long-term administration of Delta9-tetrahydrocannabinol desensitizes CB1-, adenosine A1-, and GABAB-mediated inhibition of adenylyl cyclase in mouse cerebellum.

Cannabinoid CB(1) receptors in the cerebellum mediate the inhibitory effects of Delta(9)-tetrahydrocannabinol (THC) on motor coordination. Intracellular effects of CB(1) receptors include inhibition of adenylyl cyclase via activation of G(i/o) proteins. There is evidence for the convergence of other neuronal receptors, such as adenosine A(1) and GABA(B), with the cannabinoid system on this signaling pathway to influence motor function. Previous studies have shown that brain CB(1) receptors are desensitized and down-regulated by long-term THC treatment, but few studies have examined the effects of long-term THC treatment on downstream effector activity in brain. Therefore, these studies examined the relationship between CB(1), adenosine A(1), and GABA(B) receptors in cerebella of mice undergoing prolonged treatment with vehicle or THC at the level of G protein activation and adenylyl cyclase inhibition. In control cerebella, CB(1) receptors produced less than additive inhibition of adenylyl cyclase with GABA(B) and A(1) receptors, indicating that these receptors are localized on overlapping populations of cells. Long-term THC treatment produced CB(1) receptor down-regulation and desensitization of both cannabinoid agonist-stimulated G protein activation and inhibition of forskolin-stimulated adenylyl cyclase. However, G protein activation by GABA(B) or A(1) receptors was unaffected. It is noteworthy that heterologous attenuation of GABA(B) and A(1) receptor-mediated inhibition of adenylyl cyclase was observed, even though absolute levels of basal and forskolin- or G(s)-stimulated activity were unchanged. These results indicate that long-term THC administration produces a disruption of inhibitory receptor control of cerebellar adenylyl cyclase and suggest a potential mechanism of cross-tolerance to the motor incoordinating effects of cannabinoid, GABA(B), and A(1) agonists.

Adenylyl Cyclase Inhibitors↗

(+/-)8-Amino-5,6,7,8-tetrahydroisoquinolines as novel antinociceptive agents.

Several amine-substituted 8-amino-5,6,7,8-tetrahydroisoquinolines were examined as conformationally-constrained analogs of the nicotinic cholinergic (nACh) 3-(aminomethyl)pyridines. Although these ligands failed to bind at nACh receptors, the N-ethyl-N-methyl analog 3d was found to be at least equipotent with nicotine in rodent tests of antinociception. The mechanism of action of 3d is currently unknown.

Analgesics↗