Calcium-41: a technology for monitoring changes in bone mineral

The rare, long-lived radiotracer, ⁴¹Ca, measured by accelerator mass spectrometry in the urine or serum following incorporation into the bone provides an ultra-sensitive tool to assess changes in bone calcium balance in response to an intervention. Changes in bone balance can be followed for years with one small dose that is both radiologically and biologically non-invasive. Sequential interventions can be compared, with greater precision than they can with biochemical markers of bone turnover and with greater power than with bone densitometry. This method is especially useful to screen interventions over a period of weeks. The development and validation of this tool and its applications are reviewed. Mini abstract: Use of ⁴¹Ca measured in the urine or blood by accelerator mass spectrometry to assess bone balance provides a tool to compare the relative efficacy of multiple interventions. This perspective provides insights in the use of this novel method and comparisons with more traditional methods for evaluating the efficacy of interventions.

A randomized trial of vitamin D₃ supplementation in children: dose-response effects on vitamin D metabolites and calcium absorption

CONTEXT

Changes in serum vitamin D metabolites and calcium absorption with varying doses of oral vitamin D₃ in healthy children are unknown.

OBJECTIVE

Our objective was to examine the dose-response effects of supplemental vitamin D₃ on serum vitamin D metabolites and calcium absorption in children living at two U.S. latitudes.

DESIGN

Black and white children (n = 323) participated in a multisite (U.S. latitudes 34° N and 40° N), triple-masked trial. Children were randomized to receive oral vitamin D₃ (0, 400, 1000, 2000, and 4000 IU/d) and were sampled over 12 weeks in winter. Serum 25-hydroxyvitamin D (25(OH)D) and 1,25-dihydroxyvitamin D (1,25(OH)₂D) were measured using RIA and intact PTH (iPTH) by immunoradiometric assay. Fractional calcium absorption was determined from an oral stable isotope ⁴⁴Ca (5 mg) in a 150-mg calcium meal. Nonlinear and linear regression models were fit for vitamin D metabolites, iPTH, and calcium absorption.

RESULTS

The mean baseline 25(OH)D value for the entire sample was 70.0 nmol/L. Increases in 25(OH)D depended on dose with 12-week changes ranging from -10 nmol/L for placebo to 76 nmol/L for 4000 IU. Larger 25(OH)D gains were observed for whites vs blacks at the highest dose (P < .01). Gains for 1,25(OH)₂D were not significant (P = .07), and decreases in iPTH were not dose-dependent. There was no dose effect of vitamin D on fractional calcium absorption when adjusted for pill compliance, race, sex, or baseline 25(OH)D.

CONCLUSION

Large increases in serum 25(OH)D with vitamin D₃ supplementation did not increase calcium absorption in healthy children living at 2 different latitudes. Supplementation with 400 IU/d was sufficient to maintain wintertime 25(OH)D concentrations in healthy black, but not white, children.

Racial differences in cortical bone and their relationship to biochemical variables in Black and White children in the early stages of puberty

Osteoporotic fracture rates differ according to race with Blacks having up to half the rate of Whites. The current study demonstrates that racial divergence in cortical bone properties develops in early childhood despite lower serum 25-hydroxyvitamin D in Blacks.

INTRODUCTION

Racial differences in bone structure likely have roots in childhood as bone size develops predominantly during growth. This study aimed to compare cortical bone health within the tibial diaphysis of Black and White children in the early stages of puberty and explore the contributions of biochemical variables in explaining racial variation in cortical bone properties.

METHODS

A cross-sectional study was performed comparing peripheral quantitative computed tomography-derived cortical bone measures of the tibial diaphysis and biochemical variables in 314 participants (n = 155 males; n = 164 Blacks) in the early stages of puberty.

RESULTS

Blacks had greater cortical volumetric bone mineral density, mass, and size compared to Whites (all p < 0.01), contributing to Blacks having 17.0 % greater tibial strength (polar strength-strain index (SSIP)) (p < 0.001). Turnover markers indicated that Blacks had higher bone formation (osteocalcin (OC) and bone-specific alkaline phosphatase) and lower bone resorption (N-terminal telopeptide) than Whites (all p < 0.01). Blacks also had lower 25-hydroxyvitamin D (25(OH)D) and higher 1,25-dihydroxyvitamin D (1,25(OH)2D) and parathyroid hormone (PTH) (all p < 0.05). There were no correlations between tibial bone properties and 25(OH)D and PTH in Whites (all p ≥ 0.10); however, SSIP was negatively and positively correlated with 25(OH)D and PTH in Blacks, respectively (all p ≤ 0.02). Variation in bone cross-sectional area and SSIP attributable to race was partially explained by tibial length, 25(OH)D/PTH, and OC.

CONCLUSIONS

Divergence in tibial cortical bone properties between Blacks and Whites is established by the early stages of puberty with the enhanced cortical bone properties in Black children possibly being explained by higher PTH and OC.

Pilomatrixoma: an infrequently encountered lesion on the lower extremity

We discuss the clinical presentation and treatment of pilomatrixoma as it occurs in the lower extremity. Although pilomatrixoma is far more common on the head, neck, and upper extremity, it can be found on the lower extremity. Treatment is aimed primarily at excision if the lesion is symptomatic or suspicious for malignancy. The authors present a case of a 73-year-old male who presented to the diabetic foot center with this condition.

1-Pentyl-3-phenylacetylindoles and JWH-018 share in vivo cannabinoid profiles in mice

BACKGROUND

Smoking of synthetic cannabinoid-enhanced "herbal incense" is an emerging substance abuse problem. The indole-derived cannabinoids identified in these products were originally developed as research tools and are structurally distinct from cannabinoids in the cannabis plant. Although abused by humans, most published research on this class of compounds has been performed in vitro. The purpose of this study was to evaluate a novel series of 1-pentyl-3-phenylacetylindoles in mice.

METHODS

The potencies of these analogs to produce the cannabinoid agonist effects of antinociception, hypothermia and suppression of locomotion were evaluated in ICR mice. The major structural manipulations in the present series included the type of substituent (i.e., unsubstituted, methyl, methoxy, chloro, bromo, and fluoro) and the position of the substituent on the phenyl ring (i.e., 2-, 3- or 4-position).

RESULTS

Potencies of this series of phenylacetylindoles for each cannabinoid effect were highly correlated with CB(1) receptor affinities reported previously. Active compounds produced a profile of effects that resembled that exhibited by Δ(9)-tetrahydrocannabinol (THC). The most critical factor affecting in vivo potency was the position of the substituent. Whereas compounds with 2- and 3-phenylacetyl substituents were efficacious with good potencies, 4-substituents resulted in compounds that had poor potency or were inactive.

CONCLUSIONS

These results suggest that phenylacetylindoles with good CB(1) binding affinity share pharmacological properties with THC in mice; however, they also emphasize the complexity of molecular interactions of synthetic cannabinoids with CB(1) receptors and suggest that scheduling efforts based solely upon structural features should proceed with caution.

Synthesis and pharmacology of 1-alkyl-3-(1-naphthoyl)indoles: steric and electronic effects of 4- and 8-halogenated naphthoyl substituents

To develop SAR at both the cannabinoid CB(1) and CB(2) receptors for 3-(1-naphthoyl)indoles bearing moderately electron withdrawing substituents at C-4 of the naphthoyl moiety, 1-propyl and 1-pentyl-3-(4-fluoro, chloro, bromo and iodo-1-naphthoyl) derivatives were prepared. To study the steric and electronic effects of substituents at the 8-position of the naphthoyl group, the 3-(4-chloro, bromo and iodo-1-naphthoyl)indoles were also synthesized. The affinities of both groups of compounds for the CB(1) and CB(2) receptors were determined and several of them were evaluated in vivo in the mouse. The effects of these substituents on receptor affinities and in vivo activity are discussed and structure-activity relationships are presented. Although many of these compounds are selective for the CB(2) receptor, only three JWH-423, 1-propyl-3-(4-iodo-1-naphthoyl)indole, JWH-422, 2-methyl-1-propyl-3-(4-iodo-1-naphthoyl)indole, the 2-methyl analog of JWH-423 and JWH-417, 1-pentyl-3-(8-iodo-1-naphthoyl)indole, possess the desirable combination of low CB(1) affinity and good CB(2) affinity.

Simple isotopic method using oral stable or radioactive tracers for estimating fractional calcium absorption in adult women

We extended a simple oral method for estimating fractional calcium absorption determined by double isotopic methods using radioactive or stable isotope across wide age of adult women. Fractional calcium absorption can be estimated by using either a radioactive or stable oral isotope across the entire age spectrum of adult women.

INTRODUCTION

A method for estimating fractional calcium absorption using a single serum collection following a single oral radioactive isotopic tracer has been validated against a classical double isotopic tracer ratio method in adults. Our goal was to extend this simplified method to include use of stable isotopes and a broad age range.

METHODS

We used our database of 56 observations from 26 white adult women aged 19-67 years receiving either radioactive or stable isotopes. Reference values for fractional calcium absorption were determined from 24-h double isotopic ratios in serum and urine and from full kinetic modeling.

RESULTS

Equations for estimating fractional calcium absorption were developed from isotopic enrichment in serum and urine from an oral tracer and measures of body size using the multiple linear regression analysis. Equations using a 4- to 6-h sample following an oral dose of either a stable or radioactive isotope corrected for body size were highly correlated with the reference values for fractional calcium absorption across different aged populations (r > 0.8, p < 0.001).

CONCLUSION

Fractional calcium absorption can be estimated by a single oral tracer method using either radioactive or stable calcium isotopes across the entire age spectrum in healthy white adult women.

Validation of a simple isotope method for estimating true calcium fractional absorption in adolescents

We validated a single oral isotope method for estimating fractional calcium absorption determined by double isotope methods in adolescents. Developed equations with an oral isotope including a single blood draw or spot urine collection can be used to evaluate fractional calcium absorption in adolescents which allows flexibility in developing protocols.

INTRODUCTION

This study was designed to develop and validate a simpler, less expensive single oral isotope method for determining fractional calcium (Ca) absorption in adolescents.

METHODS

We used our database of 31 observations from ten white and 12 black adolescent girls aged 10-15 years who participated in metabolic and kinetic studies. Tracer data following oral ((44)Ca) and intravenous (IV, (42)Ca) administration of calcium stable isotopes and samples in serum and urine from various time points up to 4 days were used to develop methods using multiple regression analysis based on a single measurement of enriched stable isotope/tracee defined as tracer/tracee (TT) in serum (TT(serum)) or urine (TT(urine)). Reference values for fractional calcium absorption were from oral/IV stable isotope ratios in 24-h serum or urine and full kinetic modeling.

RESULTS

The strongest equation using a single blood sample had R (2) = 0.94 (p < 0.001): fractional Ca absorption = 1.3340(4-h TT(serum))(0.7872) BSA(1.7132)e ((-0.01652 PMA)), where BSA is body surface area and PMA is post-menarcheal age. The strongest equation using a single urine sample had R (2) = 0.95 (p < 0.001): fractional Ca absorption = 2.3088 (5-12 h TT(urine))(0.8208) BSA(1.5260)e ((-0.01850 PMA)). Equations were also developed with Tanner score. An external data set of Asian adolescent boys and girls was used to validate the equations.

CONCLUSION

Equations using an oral isotope and a single blood draw or urine collection for determining fractional calcium absorption were successfully validated in healthy, non-obese white and black adolescent girls aged 10-15 years. The equations well-predicted fractional calcium absorption in Asian adolescent boys and girls.

1-Bromo-3-(1',1'-dimethylalkyl)-1-deoxy-Δ(8)-tetrahydrocannabinols: New selective ligands for the cannabinoid CB(2) receptor

Δ(8)-Tetrahydrocannabinol (26), 3-(1',1'-dimethylbutyl)- (12), 3-(1',1'-dimethylpentyl)- (13), 3-(1',1'-dimethylhexyl)- (14) and 3-(1',1'-dimethylheptyl)-Δ(8)-tetrahydrocannabinol (15) have been converted into the corresponding 1-bromo-1-deoxy-Δ(8)-tetrahydrocannabinols (25, 8-11). This was accomplished using a protocol developed in our laboratory in which the trifluoromethanesulfonate of a phenol undergoes palladium mediated coupling with pinacolborane. Reaction of this dioxaborolane with aqueous-methanolic copper(II) bromide provides the aryl bromide. The affinities of these bromo cannabinoids for the cannabinoid CB(1) and CB(2) receptors were determined. All of these compounds showed selectivity for the CB(2) receptor and one of them, 1-bromo-1-deoxy-3-(1',1'-dimethylhexyl)-Δ(8)-tetrahydrocannabinol (10), exhibits 52-fold selectivity for this receptor with good (28nM) affinity.

Synthesis and pharmacology of 1-methoxy analogs of CP-47,497

Three 1-methoxy analogs of CP-47,497 (7, 8, and 19) have been synthesized and their affinities for the cannabinoid CB(1) and CB(2) receptors have been determined. Although these compounds exhibit selectivity for the CB(2) receptor none have significant affinity for either receptor. Modeling and receptor docking studies were carried out, which provide a rationalization for the weak affinities of these compounds for either receptor.

Synthesis, nicotinic acetylcholine receptor binding, and antinociceptive properties of 3'-(substituted phenyl)epibatidine analogues. Nicotinic partial agonists

In 1992, John Daly et al. reported the isolation and structure determination of epibatidine. Epibatidine's unique structure and its potent nicotinic agonist activity have had a tremendous impact on nicotine receptor research. This research has led to a better understanding of the nicotinic acetylcholine receptor (nAChR) pharmacophore and to epibatidine analogues with potential as pharmacotherapies for treating various CNS disorders. In this study, we report the synthesis, receptor binding ([(3)H]epibatidine and [(125)I]iodoMLA), and in vivo pharmacological properties (mouse tail flick, hot plate, hypothermia, and spontaneous activity) of a series of 3'-(substituted phenyl)epibatidine analogues (5a-m). Results from these studies have added to the understanding of the nAChR pharmacophore and led to nicotinic partial agonists that may have potential for smoking cessation. All the analogues had affinities for the alpha4beta2 nAChR similar to epibatidine (1). 3'-(3-Dimethylaminophenyl)epibatidine (5m) has a nicotinic partial agonist pharmacological profile similar to the smoking cessation drug varenicline. Other analogues are partial agonists with varying degrees of nicotinic functional agonist and antagonist activity. 3'-(3-Aminophenyl)epibatidine (5j) is a more potent functional agonist and antagonist in all tests than varenicline. 3'-(3-Fluorophenyl)epibatidine and 3'-(3-chlorophenyl)epibatidine (5c and 5e) are more potent than varenicline when tested as agonists in four pharmacological tests and antagonists when evaluated against nicotine in the analgesia hot-plate test.

Antiresorptive effects of phytoestrogen supplements compared with estradiol or risedronate in postmenopausal women using (41)Ca methodology

INTRODUCTION

Reduction of ovarian estrogen secretion at menopause increases net bone resorption and leads to bone loss. Isoflavones have been reported to protect bone from estrogen deficiency, but their modest effects on bone resorption have been difficult to measure with traditional analytical methods.

METHODS

In this randomized-order, crossover, blinded trial in 11 healthy postmenopausal women, we compared four commercial sources of isoflavones from soy cotyledon, soy germ, kudzu, and red clover and a positive control of oral 1 mg estradiol combined with 2.5 mg medroxyprogesterone or 5 mg/d oral risedronate (Actonel) for their antiresorptive effects on bone using novel (41)Ca methodology.

RESULTS

Risedronate and estrogen plus progesterone decreased net bone resorption measured by urinary (41)Ca by 22 and 24%, respectively (P < 0.0001). Despite serum isoflavone profiles indicating bioavailability of the phytoestrogens, only soy isoflavones from the cotyledon and germ significantly decreased net bone resorption by 9% (P = 0.0002) and 5% (P = 0.03), respectively. Calcium absorption and biochemical markers of bone turnover were not influenced by interventions.

CONCLUSIONS

Dietary supplements containing genistein-like isoflavones demonstrated a significant but modest ability to suppress net bone resorption in postmenopausal women at the doses supplied in this study over a 50-d intervention period.

Modulation of motor and sensory pathways of the peristaltic reflex by cannabinoids

Cannabinoids have long been known to be potent inhibitors of intestinal and colonic propulsion. This effect has generally been attributed to their ability to prejunctionally inhibit release of acetylcholine from excitatory motor neurons that mediate, in part, the ascending contraction phase of the peristaltic reflex. In the present study we examined the effect of cannabinoids on the other transmitters known to participate in the peristaltic reflex using a three-compartment preparation of rat colon that allows separation of ascending contraction, descending relaxation, and the sensory components of the reflex. On addition to the orad motor compartment, anandamide decreased and AM-251, a CB-1 antagonist, increased ascending contraction and the concomitant substance P (SP) release. Similarly, on addition to the caudad motor compartment, anandamide decreased and AM-251 increased descending relaxation and the concomitant vasoactive intestinal peptide (VIP) release. On addition to the central sensory compartment, anandamide decreased and AM-251 increased both ascending contraction and SP release orad, and descending relaxation and VIP release caudad. This suggested a role for CB-1 receptors in modulation of sensory transmission that was confirmed by the demonstration that central addition of anandamide decreased and AM-251 increased release of the sensory transmitter, calcitonin gene-related peptide (CGRP). We conclude that the potent antipropulsive effect of cannabinoids is the result of inhibition of both excitatory cholinergic/tachykininergic and inhibitory VIPergic motor neurons that mediate ascending contraction and descending relaxation, respectively, as well as inhibition of the intrinsic sensory CGRP-containing neurons that initiate the peristaltic reflex underlying propulsive motility.

Characterization of pharmacological and behavioral differences to nicotine in C57Bl/6 and DBA/2 mice

Approximately 50-70% of the risk for developing nicotine dependence is attributed to genetics; therefore, it is of great significance to characterize the genetic mechanisms involved in nicotine reinforcement and dependence in hopes of generating better smoking cessation therapies. The overall goal of these studies was to characterize behavioral and pharmacological responses to nicotine in C57Bl/6 (B6) and DBA/2 (D2) mice, two inbred strains commonly used for genetic studies on behavioral traits. B6 and D2 mice where subjected to a battery of behavioral tests to measure nicotine's acute effects, calcium-mediated antinociceptive responses, tolerance to chronic treatment with osmotic mini pumps, and following three days of nicotine withdrawal. In general, D2 mice were less sensitive than B6 mice to the acute effects of nicotine, but were more sensitive to blockade of nicotine-induced antinociceptive responses by a calcium/calmodulin-dependent protein kinase II (CaMKII) inhibitor. B6, but not D2 mice, developed tolerance to nicotine and nicotine conditioned place preference (CPP). While B6 and D2 mice both expressed some physical withdrawal signs, affective withdrawal signs were not evident in D2 mice. These results provide a thorough, simultaneous evaluation of the pharmacological and behavioral differences to experimenter-administered nicotine as measured in several behavioral tests of aspects that contribute to smoking behavior. The B6 and D2 strains show wide phenotypic differences in their responses to acute or chronic nicotine. These results suggest that these strains may be useful progenitors for future genetic studies on nicotine behaviors across batteries of mouse lines such as the BXD recombinant inbred panel.

Prolonged exposure to WIN55,212-2 causes downregulation of the CB1 receptor and the development of tolerance to its anticonvulsant effects in the hippocampal neuronal culture model of acquired epilepsy

Cannabinoids have been shown to cause CB1-receptor-dependent anticonvulsant activity in both in vivo and in vitro models of status epilepticus (SE) and acquired epilepsy (AE). It has been further demonstrated in these models that the endocannabinoid system functions in a tonic manner to suppress seizure discharges through a CB1-receptor-dependent pathway. Although acute cannabinoid treatment has anticonvulsant activity, little is known concerning the effects of prolonged exposure to CB1 agonists and development of tolerance on the epileptic phenotype. This study was carried out to evaluate the effects of prolonged exposure to the CB1 agonist WIN55,212-2 on seizure activity in a hippocampal neuronal culture model of low-Mg(2+) induced spontaneous recurrent epileptiform discharges (SREDs). Following low-Mg(2+) induced SREDs, cultures were returned to maintenance media containing 10, 100 or 1000 nM WIN55,212-2 from 4 to 24 h. Whole-cell current-clamp analysis of WIN55,212-2 treated cultures revealed a concentration-dependent increase in SRED frequency. Immunocytochemical staining revealed that WIN55,212-2 treatment induced a concentration-dependent downregulation of the CB1 receptor in neuronal processes and at both glutamatergic and GABAergic presynaptic terminals. Prolonged exposure to the inactive enantiomer WIN55,212-3 in low-Mg(2+) treated cultures had no effect on the frequency of SREDs or CB1 receptor staining. The results from this study further substantiate a role for a tonic CB1-receptor-dependent endocannabinoid regulation of seizure discharge and suggest that prolonged exposure to cannabinoids results in the development of tolerance to the anticonvulsant effects of cannabinoids and an exacerbation of seizure activity in the epileptic phenotype.

Discriminative stimulus properties of delta9-tetrahydrocannabinol (THC) in C57Bl/6J mice

Primarily, rats have served as subjects in Delta(9)-tetrahydrocannabinol's (THC) discrimination studies although other species such as monkeys and pigeons have been used. While the introduction of the knockout and transgenic mice has vastly stimulated the study of the discriminative stimulus effects of drugs there is only a single published report of mice trained to discriminate THC. Thus, this study extended those results by providing a systematic replication that THC serves as an effective discriminative stimulus in mice and by further investigating the mechanisms of action involved in the THC discrimination model in the mouse. Male C57BL/6J mice were trained to discriminate 10 mg/kg THC from vehicle in 2-lever drug discrimination. THC fully and dose dependently substituted for itself. Cannabinoid indoles, except one with low cannabinoid CB(1) receptor affinity, substituted for THC. Anandamide failed to substitute for THC when administered alone but completely substituted when administered with the non-specific fatty acid amide hydrolase inhibitor, phenylmethylsulphonyl fluoride. As expected, nicotine failed to substitute for THC. Lastly, the cannabinoid CB(1) receptor antagonist rimonabant blocked THC's discriminative stimulus effects. Taken together these studies demonstrate THC's ability to produce discriminative stimulus effects as well as demonstrate its pharmacological specificity and mechanism of action in a two-lever drug discrimination mouse model.

Modulation of cannabinoid receptor activation as a neuroprotective strategy for EAE and stroke

Recognition of the importance of the endocannabinoid system in both homeostasis and pathologic responses raised interest recently in the development of therapeutic agents based on this system. The CB(2) receptor, a component of the endocannabinoid system, has significant influence on immune function and inflammatory responses. Inflammatory responses are major contributors to central nervous system (CNS) injury in a variety of diseases. In this report, we present evidence that activation of CB(2) receptors, by selective CB(2) agonists, reduces inflammatory responses that contribute to CNS injury. The studies demonstrate neuroprotective effects in experimental autoimmune encephalomyelitis, a model of multiple sclerosis, and in a murine model of cerebral ischemia/reperfusion injury. In both cases, CB(2) receptor activation results in reduced white cell rolling and adhesion to cerebral microvessels, a reduction in immune cell invasion, and improved neurologic function after insult. In addition, administration of the CB(1) antagonist SR141716A reduces infarct size following ischemia/reperfusion injury. Administration of both a selective CB(2) agonist and a CB(1) antagonist has the unique property of increasing blood flow to the brain during the occlusion period, suggesting an effect on collateral blood flow. In summary, selective CB(2) receptor agonists and CB(1) receptor antagonists have significant potential for neuroprotection in animal models of two devastating diseases that currently lack effective treatment options.

The role of various nicotinic receptor subunits and factors influencing nicotine conditioned place aversion

Affective nicotine withdrawal symptoms are of major motivational significance in contributing to relapse and continued tobacco use; thus, it is important to understand the molecular and receptor-mediated mechanisms that mediate affective withdrawal behaviors. Previous work using the conditioned place aversion (CPA) model has shown that nicotine withdrawal is associated with a negative affective state, and place aversion to previously neutral environmental stimuli represents a motivational component in the maintenance of drug use. Thus, the purpose of this study was to evaluate the role of genotype, sex, and age and to extend previous studies examining the role of various nicotinic receptor subtypes in the development of nicotine withdrawal aversion using the CPA model. Mice were chronically treated with nicotine and conditioned for two days with various nicotinic receptor antagonists. The major findings showed that mecamylamine and dihydro-beta-erythroidine (DHbetaE), but not hexamethonium or methyllycaconitine citrate (MLA), precipitated significant aversion in the CPA model. This pharmacological data support our previous knockout mouse data suggesting that nicotine CPA is mediated by central beta2-containing nicotinic receptors, but not alpha7 nicotinic receptors. Further, we show that sex and age are contributing factors to the development of nicotine CPA. Overall, the results of our study provide some insight into pharmacological and behavioral factors involved in the development of an aversive motivational component associated with nicotine withdrawal.

Temporal characterization of changes in hippocampal cannabinoid CB(1) receptor expression following pilocarpine-induced status epilepticus

Several reports have focused on the involvement of the endocannabinoid system in hyperexcitability, particularly in seizure and epilepsy models. Our laboratory recently characterized a novel plasticity change of the cannabinoid type 1 (CB(1)) receptor in hippocampi of epileptic rats following pilocarpine-induced status epilepticus (SE). This long-term redistribution included selective layer-specific changes in CB(1) receptor expression within distinct hippocampal subregions. However, the temporal characteristics of this redistribution during the development of epilepsy had not been examined. Therefore, this study was initiated to evaluate the time course by which pilocarpine-induced SE produced changes in CB(1) receptor expression. Immunohistochemical analysis demonstrated that within 1 week following SE, there was a pronounced loss in CB(1) receptor expression throughout the hippocampus, while staining in many interneurons was preserved. By 1 month post-SE, pilocarpine-treated animals began to display epileptic seizures, and CB(1) receptor expression was characteristic of the redistribution observed in long-term epileptic rats, with decreases in CB(1) receptor immunoreactivity in the stratum pyramidale neuropil and dentate gyrus inner molecular layer, and increases in the strata oriens and radiatum of CA1-3. Observed changes in CB(1) receptor expression were confirmed at multiple time points by western blot analysis. The data indicate that overall decreases in expression following SE preempt a long-lasting CB(1) receptor redistribution, and that differential responses occur within the hippocampus to initial CB(1) receptor losses. This suggests a role for dysregulation of the endocannabinoid system during epileptogenesis and indicates that the CB(1) receptor redistribution temporally correlates with the emergence of epileptic seizures.

3'-Fluoro substitution in the pyridine ring of epibatidine improves selectivity and efficacy for alpha4beta2 versus alpha3beta4 nAChRs

The analog of epibatidine having a fluoro substituent at the 3' position of the pyridine ring has been recently developed and shown to possess binding affinity in the pM range to alpha4beta2 nAChRs and in the nM range to alpha7 nAChRs and to exhibit potent agonist activity in nicotine-induced analgesia tests. Here we used patch-clamp technique in a whole-cell configuration to compare functional activity of 3'-fluoroepibatidine to that of epibatidine by itself on recombinant alpha4beta2, alpha7 and alpha3beta4 neuronal nAChRs. The agonist effect of (+/-)-epibatidine was partial and yielded comparable EC50s of 0.012 microM (72% efficacy) and 0.027 microM (81% efficacy) at alpha4beta2 and alpha3beta4 nAChRs, respectively, but was full at alpha7 nAChRs with an EC50 of 4.8 muM. Testing of the analog at different concentrations revealed that it acts as a full agonist with an EC50 of 0.36 microM at alpha4beta2 nAChRs and induces partial agonist effect (66% efficacy) at alpha7 nAChRs with an EC50 of 9.8 microM and an IC50 corresponding to 225 microM. In contrast, the analog caused only 24% maximal activation at the range of concentrations from 0.1 to 100 microM and, in addition, induced an inhibition of alpha3beta4 nAChR function with an IC50 of 8.3 microM. Our functional data, which are in agreement with previous binding and behavioral findings, demonstrate that 3'-fluoro substitution in the pyridine ring of epibatidine results in an improved pharmacological profile as observed by an increased efficacy and selectivity for alpha4beta2 versus alpha3beta4 nAChRs.

Distinct patterns of DeltaFosB induction in brain by drugs of abuse

The transcription factor DeltaFosB accumulates and persists in brain in response to chronic stimulation. This accumulation after chronic exposure to drugs of abuse has been demonstrated previously by Western blot most dramatically in striatal regions, including dorsal striatum (caudate/putamen) and nucleus accumbens. In the present study, we used immunohistochemistry to define with greater anatomical precision the induction of DeltaFosB throughout the rodent brain after chronic drug treatment. We also extended previous research involving cocaine, morphine, and nicotine to two additional drugs of abuse, ethanol and Delta(9)-tetrahydrocannabinol (Delta(9)-THC, the active ingredient in marijuana). We show here that chronic, but not acute, administration of each of four drugs of abuse, cocaine, morphine, ethanol, and Delta(9)-THC, robustly induces DeltaFosB in nucleus accumbens, although different patterns in the core vs. shell subregions of this nucleus were apparent for the different drugs. The drugs also differed in their degree of DeltaFosB induction in dorsal striatum. In addition, all four drugs induced DeltaFosB in prefrontal cortex, with the greatest effects observed with cocaine and ethanol, and all of the drugs induced DeltaFosB to a small extent in amygdala. Furthermore, all drugs induced DeltaFosB in the hippocampus, and, with the exception of ethanol, most of this induction was seen in the dentate. Lower levels of DeltaFosB induction were seen in other brain areas in response to a particular drug treatment. These findings provide further evidence that induction of DeltaFosB in nucleus accumbens is a common action of virtually all drugs of abuse and that, beyond nucleus accumbens, each drug induces DeltaFosB in a region-specific manner in brain.

The cannabinoid delta-9-tetrahydrocannabinol mediates inhibition of macrophage chemotaxis to RANTES/CCL5: linkage to the CB2 receptor

The chemotactic response of murine peritoneal macrophages to RANTES/CCL5 was inhibited significantly following pretreatment with delta-9-tetrahydrocannabinol (THC), the major psychoactive component in marijuana. Significant inhibition of this chemokine directed migratory response was obtained also when the full cannabinoid agonist CP55940 was used. The CB2 receptor-selective ligand O-2137 exerted a robust inhibition of chemotaxis while the CB1 receptor-selective ligand ACEA had a minimal effect. The THC-mediated inhibition was reversed by the CB2 receptor-specific antagonist SR144528 but not by the CB1 receptor-specific antagonist SR141716A. In addition, THC treatment had a minimal effect on the chemotactic response of peritoneal macrophages from CB2 knockout mice. Collectively, these results suggest that cannabinoids act through the CB2 receptor to transdeactivate migratory responsiveness to RANTES/CCL5. Furthermore, the results suggest that the CB2 receptor may be a constituent element of a network of G protein-coupled receptor signal transductional systems, inclusive of chemokine receptors, that act coordinately to modulate macrophage migration.

Age-dependent differences in nicotine reward and withdrawal in female mice

RATIONALE

Adolescent smoking is an increasing epidemic in the US. Research has shown that the commencement of smoking at a young age increases addiction and decreases the probability of successful cessation; however, limited work has focused on nicotine dependence in the female.

OBJECTIVE

The goal of the present study was to identify the biological and behavioral factors that may contribute to nicotine's increased abuse liability in female adolescents using animal models of nicotine dependence.

MATERIALS AND METHODS

Early adolescent (PND 28) and adult (PND 70) female mice were compared in various aspects of nicotine dependence using reward and withdrawal models following sub-chronic nicotine exposure. Furthermore, in vivo acute sensitivity and tolerance to nicotine were examined.

RESULTS

In the conditioned place preference model, adolescents demonstrated a significant preference at 0.5 mg/kg nicotine, an inactive dose in adults. Adults found higher doses (0.7 and 1.0 mg/kg) of nicotine to elicit rewarding effects. Furthermore, adolescents displayed increased physical, but not affective, withdrawal signs in three models. Upon acute exposure to nicotine, adolescent mice showed increased sensitivity in an analgesic measure as well as hypothermia. After chronic nicotine exposure, both adults and adolescents displayed tolerance to nicotine with adolescents having a lower degree of tolerance to changes in body temperature.

CONCLUSIONS

These data indicate that differences in nicotine's rewarding and aversive effects may contribute to variations in certain components of nicotine dependence between adult and adolescent female mice. Furthermore, this implies that smoking cessation therapies may not be equally effective across all ages.

The endogenous cannabinoid system modulates nicotine reward and dependence

A growing body of evidence suggests that the endogenous cannabinoid system modulates the addictive properties of nicotine, the main component of tobacco that produces rewarding effects. In our study, complementary transgenic and pharmacological approaches were used to test the hypothesis that the endocannabinoid system modulates nicotine reward and dependence. An acute injection of nicotine elicited normal analgesic and hypothermic effects in cannabinoid receptor (CB)(1) knockout (KO) mice and mice treated with the CB(1) antagonist rimonabant. However, disruption of CB(1) receptor signaling blocked nicotine reward, as assessed in the conditioned place preference (CPP) paradigm. In contrast, genetic deletion, or pharmacological inhibition of fatty acid amide hydrolase (FAAH), the enzyme responsible for catabolism of the endocannabinoid anandamide, enhanced the expression of nicotine CPP. Although the expression of spontaneous nicotine withdrawal (14 days, 24 mg/kg/day nicotine) was unaffected in CB(1) KO mice, acute administration of rimonabant (3 mg/kg) ameliorated somatic withdrawal signs in wild-type mice. Increasing endogenous levels of anandamide through genetic or pharmacological approaches exacerbated the physical somatic signs of spontaneous nicotine withdrawal in a milder withdrawal model (7 days, 24 mg/kg/day nicotine). Moreover, FAAH-compromised mice displayed increased conditioned place aversion in a mecamylamine-precipitated model of nicotine withdrawal. These findings indicate that endocannabinoids play a role in the rewarding properties of nicotine as well as nicotine dependence liability. Specifically, increasing endogenous cannabinoid levels magnifies, although disrupting CB(1) receptor signaling, attenuates nicotine reward and withdrawal. Taken together, these results support the hypothesis that cannabinoid receptor antagonists may offer therapeutic advantages to treat tobacco dependence.

A soybean cultivar lacking lipoxygenase 2 and 3 has similar calcium bioavailability to a commercial variety despite higher calcium absorption inhibitors

The aim of this study was to evaluate calcium bioavailability of a new soybean variety without 2 lipoxygenases with better taste and flavor than a commercial variety containing all 3 isozymes. Using the femur (45)Ca uptake method, calcium absorption from a new Brazilian variety, UFV-116, was compared to a common Brazilian variety, OCEPAR 19. Male Sprague-Dawley growing rats weighing 150 to 170 g (10/group) received test meals of whole fat soy flour prepared from UFV-116 or OCEPAR-19 seeds labeled with 10 microCi of (45)Ca. Femurs were removed after 48 h for determination of (45)Ca uptake. Calcium fractional absorption was equivalent between the 2 varieties. The higher oxalate:calcium molar ratio and the higher content of oxalate and phytate (P < 0.05) found in the UFV-116 variety did not affect calcium absorption. Therefore, the new variety is a comparable source of high bioavailable calcium.

Divergent effects of cannabidiol on the discriminative stimulus and place conditioning effects of Delta(9)-tetrahydrocannabinol

Cannabis sativa (marijuana plant) contains myriad cannabinoid compounds; yet, investigative attention has focused almost exclusively on Delta(9)-tetrahydrocannabinol (THC), its primary psychoactive substituent. Interest in modulation of THC's effects by these other cannabinoids (e.g., cannabidiol (CBD)) has been stimulated anew by recent approval by Canada of Sativex (a 1:1 dose ratio combination of CBD:THC) for the treatment of multiple sclerosis. The goal of this study was to determine the degree to which THC's abuse-related effects were altered by co-administration of CBD. To this end, CBD and THC were assessed alone and in combination in a two-lever THC discrimination procedure in Long-Evans rats and in a conditioned place preference/aversion (CPP/A) model in ICR mice. CBD did not alter the discriminative stimulus effects of THC at any CBD:THC dose ratio tested. In contrast, CBD, at CBD:THC dose ratios of 1:1 and 1:10, reversed CPA produced by acute injection with 10mg/kg THC. When administered alone, CBD did not produce effects in either procedure. These results suggest that CBD, when administered with THC at therapeutically relevant ratios, may ameliorate aversive effects (e.g., dysphoria) often associated with initial use of THC alone. While this effect may be beneficial for therapeutic usage of a CBD:THC combination medication, our discrimination results showing that CBD did not alter THC's discriminative stimulus effects suggest that CBD:THC combination medications may also produce THC-like subjective effects at these dose ratios.

Differential role of nicotinic acetylcholine receptor subunits in physical and affective nicotine withdrawal signs

It has been suggested that the negative effects associated with nicotine withdrawal promote continued tobacco use and contribute to the high relapse rate of smoking behaviors. Thus, it is important to understand the receptor-mediated mechanisms underlying nicotine withdrawal to aid in the development of more successful smoking cessation therapies. The effects of nicotine withdrawal are mediated through nicotinic acetylcholine receptors (nAChRs); however, the role of nAChRs in nicotine withdrawal remains unclear. Therefore, we used mecamylamine-precipitated, spontaneous, and conditioned place aversion (CPA) withdrawal models to measure physical and affective signs of nicotine withdrawal in various nAChR knockout (KO) mice. beta2, alpha7, and alpha5 nAChR KO mice were chronically exposed to nicotine through surgically implanted osmotic minipumps. Our results show a loss of anxiety-related behavior and a loss of aversion in the CPA model in beta2 KO mice, whereas alpha7 and alpha5 KO mice displayed a loss of nicotine withdrawal-induced hyperalgesia and a reduction in somatic signs, respectively. These results suggest that beta2-containing nAChRs are involved in the affective signs of nicotine withdrawal, whereas non-beta2-containing nAChRs are more closely associated with physical signs of nicotine withdrawal; thus, the nAChR subtype composition may play an important role in the involvement of specific subtypes in nicotine withdrawal.

Synthesis and pharmacology of 1-deoxy analogs of CP-47,497 and CP-55,940

A series of 1-deoxy analogs of CP-47,497 (8 and 13, n=0-7) and 1-deoxy analogs of CP-55,940 (9, n=0-7) have been synthesized and their affinities for the cannabinoid CB(1) and CB(2) receptors have been determined. Although the majority of these compounds exhibit selectivity for the CB(2) receptor, none have greater than modest affinity for either receptor. The interactions of these 1-deoxy nontraditional cannabinoids with the CB(2) receptor are discussed.

Novel, potent THC/anandamide (hybrid) analogs

The structure-activity relationship (SAR) of the end pentyl chain in anandamide (AEA) has been established to be very similar to that of Delta(9)-tetrahydrocannabinol (Delta(9)-THC). In order to broaden our understanding of the structural similarities between AEA and THC, hybrid structures 1-3 were designed. In these hybrids the aromatic ring of THC-DMH was linked to the AEA moiety through an ether linkage with the oxygen of the phenol of THC. Hybrid 1 (O-2220) was found to have very high binding affinity to CB1 receptors (K(i)=8.5 nM), and it is interesting to note that the orientation of the side chain with respect to the oxygen in the phenol is the same as in THCs. To further explore the SAR in this series the terminal carbon of the side chain was modified by adding different substituents. Several such analogs were synthesized and tested for their CB1 and CB2 binding affinities and in vivo activity (tetrad tests). The details of the synthesis and the biological activity of these compounds are described.

Zinc and iron bioavailability of genetically modified soybeans in rats

The aim of this work was to evaluate zinc and iron bioavailability of UFV-116, a new variety without 2 lipoxygenases, with better taste and flavor than a commercial variety OCEPAR 19, containing all 3 isozymes. To evaluate zinc absorption using 65Zn whole body retention and femur 65Zn uptake, rats were given 3 g of a 65ZnCl2 labeled test meal (0.25 microCi). The 2 varieties were tested at the level of 9 and 30 ppm of zinc as defatted soy flour. Two other groups (control) received egg white as source of protein and ZnS04.H20 as the zinc source. To evaluate iron absorption, using 59Fe whole body retention, animals were given a 3 g 59FeCl3 labeled test meal (0.2 microCi). The 2 varieties were tested at 12 and 25 ppm iron as defatted soy flour. Whole fat soy flour of variety 1 (UFV-116) was higher (P < 0.05) in Ca, K, Mg, phytic acid, and oxalate than variety 2 (OCEPAR-19). No difference was observed among the soybean varieties (P > 0.05) for femur 65Zn retention, at different levels of zinc. However, whole body retention was lower (P < 0.05) for UFV-116 than for OCEPAR-19. Femur 65Zn uptake was correlated with the whole body retention; however, whole body retention was more sensitive. Whole body 59Fe retention from UFV-116 was lower (P < 0.05) than from OCEPAR-19. Zinc and iron bioavailability was lower for UFV-116, possibly due to its higher content of antinutrient factors, especially phytate.

Dose-related differences in the regional pattern of cannabinoid receptor adaptation and in vivo tolerance development to delta9-tetrahydrocannabinol

Chronic treatment with Delta(9)-tetrahydrocannabinol (THC) produces tolerance to cannabinoid-mediated behaviors and region-specific adaptation of brain cannabinoid receptors. However, the relationship between receptor adaptation and tolerance is not well understood, and the dose-response relationship of THC-induced cannabinoid receptor adaptation is unknown. This study assessed cannabinoid receptor function in the brain and cannabinoid-mediated behaviors after chronic treatment with different dosing regimens of THC. Mice were treated twice per day for 6.5 days with the following: vehicle, 10 mg/kg THC, or escalating doses of 10 to 20 to 30 or 10 to 30 to 60 mg/kg THC. Tolerance to cannabinoid-mediated locomotor inhibition, ring immobility, antinociception, and hypothermia was produced by both ramping THC-dose paradigms. Administration of 10 mg/kg THC produced less tolerance development, the magnitude of which depended upon the particular behavior. Decreases in cannabinoid-mediated G-protein activation, which varied with treatment dose and region, were observed in autoradiographic and membrane guanosine 5'-O-(3-[(35)S]thio)triphosphate ([(35)S]GTPgammaS)-binding assays in brains from THC-treated mice. Agonist-stimulated [(35)S]GTPgammaS binding was reduced in the hippocampus, cingulate cortex, periaqueductal gray, and cerebellum after all treatments. Decreased agonist-stimulated [(35)S]GTPgammaS binding in the caudate-putamen, nucleus accumbens, and preoptic area occurred only after administration of 10 to 30 to 60 mg/kg THC, and no change was found in the globus pallidus or entopeduncular nucleus after any treatment. Changes in the CB(1) receptor B(max) values also varied by region, with hippocampus and cerebellum showing reductions after all treatments and striatum/globus pallidus showing effects only at higher dosing regimens. These results reveal that tolerance and CB(1) receptor adaptation exhibit similar dose-dependent development, and they are consistent with previous studies demonstrating less cannabinoid receptor adaptation in striatal circuits.

Synthesis, nicotinic acetylcholine receptor binding, and pharmacological properties of 3'-(substituted phenyl)deschloroepibatidine analogs

A series of 3'-(substituted phenyl)deschloroepibatidine analogs (5a-j) were synthesized. The alpha4beta2( *) and alpha7 nicotinic acetylcholine receptor (nAChR) binding properties and functional activity in the tail-flick, hot-plate, locomotor, and body temperature tests in mice of 5a-j were compared to those of the nAChR agonist, nicotine (1), epibatidine (4), and deschloroepibatidine (13), the partial agonist, varenicline (3), and the antagonist 2'-fluoro-3'-(substituted phenyl)deschloroepibatidine analogs (7a-j). Unlike epibatidine and deschloroepibatidine, which are potent agonists in the tail-flick test, 5a-k show no or very low antinociceptive activity in the tail-flick or hot-plate test. However, they are potent antagonists in nicotine-induced antinociception in the tail-flick test, but weaker than the corresponding 2'-fluoro-3'-(substituted phenyl)deschloroepibatidines.

Lack of behavioral sensitization after repeated exposure to THC in mice and comparison to methamphetamine

RATIONALE

Recent evidence has provided support for the incentive-sensitization model of addiction, where repeated stimulation of neural reward circuits leads to a long-lasting sensitization of mesolimbic dopaminergic activity. This phenomenon has been demonstrated with many drugs of abuse, most often by measuring progressively increased activating effects of drugs on locomotor activity, thought to reflect an underlying neural sensitization. Whether cannabinoids, and in particular Delta(9)-tetrahydrocannabinol (THC), produce similar effects in this model is somewhat controversial, with mixed evidence in the literature.

OBJECTIVES

These experiments were conducted to determine whether behavioral sensitization could be established in mice after repeated exposure to THC. Sensitization to repeated methamphetamine treatment was used as a positive control.

METHODS

The effects of acute and repeated intermittent (every 3-4 days) treatment with THC or methamphetamine on locomotor activity were determined in Institute of Cancer Research (ICR) mice. Additional experiments with THC employed a dosing regimen that increased the number of injections, controlled for behavioral tolerance, examined different aspects of behavior, and used a different species (Sprague-Dawley rats).

RESULTS

Both methamphetamine and THC acutely increased activity. A robust dose-dependent sensitization was observed after intermittent treatment with methamphetamine but not with THC. Additionally, no evidence for behavioral sensitization to the effects of THC was found with any of the various protocols.

CONCLUSION

These data suggest that repeated THC treatment is less likely to produce behavioral sensitization than are other drugs of abuse. It appears that this phenomenon may only occur under very particular conditions, which raises doubts about its relevance to chronic cannabis users.

Significance of cannabinoid CB1 receptors in improgan antinociception

Improgan is a congener of the H(2) antagonist cimetidine, which produces potent antinociception. Because a) the mechanism of action of improgan remains unknown and b) this drug may indirectly activate cannabinoid CB(1) receptors, the effects of the CB(1) antagonist/inverse agonist rimonabant (SR141716A) and 3 congeners with varying CB(1) potencies were studied on improgan antinociception after intracerebroventricular (icv) dosing in rats. Consistent with blockade of brain CB(1) receptors, rimonabant (K(d) = 0.23 nM), and O-1691 (K(d) = 0.22 nM) inhibited improgan antinociception by 48% and 70% after icv doses of 43 nmol and 25 nmol, respectively. However, 2 other derivatives with much lower CB(1) affinity (O-1876, K(d) = 139 nM and O-848, K(d) = 352 nM) unexpectedly blocked improgan antinociception by 65% and 50% after icv doses of 300 nmol and 30 nmol, respectively. These derivatives have 600-fold to 1500-fold lower CB(1) potencies than that of rimonabant, yet they retained improgan antagonist activity in vivo. In vitro dose-response curves with (35)S-GTPgammaS on CB(1) receptor-containing membranes confirmed the approximate relative potency of the derivatives at the CB(1) receptor. Although antagonism of improgan antinociception by rimonabant has previously implicated a mechanistic role for the CB(1) receptor, current findings with rimonabant congeners suggest that receptors other than, or in addition to CB(1) may participate in the pain-relieving mechanisms activated by this drug. The use of congeners such as O-848, which lack relevant CB(1)-blocking properties, will help to identify these cannabinoid-like, non-CB(1) mechanisms.

PERSPECTIVE

This article describes new pharmacological characteristics of improgan, a pain-relieving drug that acts by an unknown mechanism. Improgan may use a marijuana-like (cannabinoid) pain-relieving mechanism, but it is shown presently that the principal cannabinoid receptor in the brain (CB(1)) is not solely responsible for improgan analgesia.

Cannabinoid CB(2) receptor activation decreases cerebral infarction in a mouse focal ischemia/reperfusion model

Cannabinoid CB(2) Receptor (CB(2)) activation has been shown to have immunomodulatory properties without psychotropic effects. The hypothesis of this study is that selective CB(2) agonist treatment can attenuate cerebral ischemia/reperfusion injury. Selective CB(2) agonists (O-3853, O-1966) were administered intravenously 1 h before transient middle cerebral artery occlusion (MCAO) or 10 mins after reperfusion in male mice. Leukocyte/endothelial interactions were evaluated before MCAO, 1 h after MCAO, and 24 h after MCAO via a closed cranial window. Cerebral infarct volume and motor function were determined 24 h after MCAO. Administration of the selective CB(2) agonists significantly decreased cerebral infarction (30%) and improved motor function (P<0.05) after 1 h MCAO followed by 23 h reperfusion in mice. Transient ischemia in untreated animals was associated with a significant increase in leukocyte rolling and adhesion on both venules and arterioles (P<0.05), whereas the enhanced rolling and adhesion were attenuated by both selective CB(2) agonists administered either at 1 h before or after MCAO (P<0.05). CB(2) activation is associated with a reduction in white blood cell rolling and adhesion along cerebral vascular endothelial cells, a reduction in infarct size, and improved motor function after transient focal ischemia.

Exposure to Marijuana Smoke Impairs Memory Retrieval in Mice

Marijuana (Cannabis sativa) and its primary psychoactive component, delta-9-tetrahydrocannabinol (Delta(9)-THC), have long been known to disrupt cognition in humans. Although Delta(9)-THC and other cannabinoids disrupt performance in a wide range of animal models of learning and memory, few studies have investigated the effects of smoked marijuana in these paradigms. Moreover, in preclinical studies, cannabinoids are generally administered before acquisition, and because retention is generally evaluated soon afterward, it is difficult to distinguish between processes related to acquisition and retrieval. In the present study, we investigated the specific effects of marijuana smoke and injected Delta(9)-THC on acquisition versus memory retrieval in a mouse repeated acquisition Morris water-maze task. To distinguish between these processes, subjects were administered Delta(9)-THC or they were exposed to marijuana smoke either 30 min before acquisition or 30 min before the retention test. Inhalation of marijuana smoke or injected Delta(9)-THC impaired the ability of the mice to learn the location of the hidden platform and to recall the platform location once learning had already taken place. In contrast, neither drug impaired performance in a cued task in which the platform was made visible. Finally, the cannabinoid-1 (CB(1)) receptor antagonist N-(piperidin-1-yl)-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide HCl (rimonabant) blocked the memory disruptive effects of both Delta(9)-THC and marijuana. These data represent the first evidence demonstrating that marijuana impairs memory retrieval through a CB(1) receptor mechanism of action and independently of its effects on sensorimotor performance, motivation, and initial acquisition.

Evaluation of fatty acid amide hydrolase inhibition in murine models of emotionality

RATIONALE

Manipulations of the endocannabinoid/fatty acid amide hydrolase (FAAH) signaling systems result in conflicting and paradoxical effects in rodent models of emotional reactivity.

OBJECTIVES

In the present study, we tested the hypothesis that the inhibition of FAAH would elicit significant effects in murine models used to screen anxiolytic and antidepressant drugs.

MATERIALS AND METHODS

FAAH (-/-) mice and wild-type mice treated with FAAH inhibitors (URB597 and OL-135) were evaluated in standard behavioral screening models for antidepressant (i.e., tail suspension and forced-swim tests) and anxiolytic (i.e., elevated plus maze) agents. The doses of URB597 and OL-135 selected were based on their ability to augment the pharmacological effects (i.e., analgesia, catalepsy, and hypothermia) of exogenously administered anandamide.

RESULTS

FAAH (-/-) mice, anandamide-injected FAAH (-/-) mice, or wild-type mice injected with FAAH inhibitors or anandamide failed to exhibit significant effects in standard tests of emotional reactivity, although the antidepressant desipramine and the anxiolytic agent midazolam were active in the appropriate assays. FAAH- (-/-) and URB597-treated mice finally displayed significant effects in the tail suspension test when substantial methodological changes were made (i.e., altered ambient light and increased sample sizes).

CONCLUSIONS

Although FAAH suppression can elicit significant effects under some instances in which consequential procedural modifications are made, the present results indicate that the pharmacological inhibition or genetic deletion of FAAH is ineffective in standard mouse models of emotional reactivity. It remains to be established whether the effects of FAAH inhibition in these modified tasks are predictive of their efficacy in treating emotional disorders.

Nicotine Dependence and Reward Differ between Adolescent and Adult Male Mice

The present study defined age differences in several aspects of nicotine dependence using male mice of two age groups [postnatal day (PND) 28 and PND 70]. Adolescent and adult mice displayed differences in acute sensitivity to nicotine, rewarding and withdrawal effects, development of tolerance to nicotine, and nicotinic receptor function. In the condition place preference model, adolescent mice displayed a higher sensitivity to nicotine than adults. In addition, in spontaneous and mecamylamine-precipitated withdrawal models, adolescent mice displayed fewer withdrawal signs than adults. In response to acute nicotine, it was found that adolescent mice displayed greater nicotine-induced antinociception compared with adult counterparts in the tail-flick test. Furthermore, differences in tolerance to nicotine were also noted in that adolescents developed a significantly higher degree of tolerance to nicotine in the hot-plate test compared with adults. Finally, using rubidium efflux assays, it was found that adolescent nicotinic receptors in different brain areas displayed significantly increased functionality compared with adult receptors. These data indicate that the underlying receptor mechanisms of nicotine dependence differ for adults and adolescents, suggesting that the effectiveness of smoking cessation therapies will differ for various age groups.

Genetic Approaches Identify Differential Roles for α4β2*Nicotinic Receptors in Acute Models of Antinociception in Mice

The effects of nicotine on the tail-flick and hot-plate tests were determined to identify nicotinic receptor subtypes responsible for spinally and supraspinally mediated nicotine analgesia in knockin mice expressing hypersensitive alpha(4) nicotinic receptors (L9'S), in seven inbred mouse strains (C57BL/6, DBA/2, A/2, CBA/2, BALB/cByJ, C3H/HeJ, and 129/SvEv), and in two F1 hybrids (B6CBAF1 and B6D2F1). L9'S heterozygotes were approximately 6-fold more sensitive to the antinociceptive effects of nicotine than the wild-type controls in the hot-plate test but not in the tail-flick assay. Large differences in the effects of nicotine were also observed with both tests for the seven mouse strains. A/J and 129 mice were 6- to 8-fold more sensitive than CBA and BALB mice. In addition, B6CBAF1 hybrid mice were even less sensitive than CBA mice. Nicotinic binding sites were measured in three spinal cord regions and the hindbrain of the inbred strains. Significant differences in cytisine-sensitive, high affinity [(125)I]epibatidine binding site levels (alpha(4)beta(2)(*) subtypes), but not in (125)I-alpha-bungarotoxin binding (alpha(7)(*) subtypes), were observed. Significant negative correlations between cytisine-sensitive [(125)I]epibatidine binding and nicotine ED(50) for both tests were noted. Our results indicate that alpha(4)beta(2)(*) acetylcholine nicotinic receptors (nAChR) are important in mediating nicotine analgesia in supraspinal responses, while also showing that alpha(4)beta(2)(*)-nAChR and at least one other nAChR subtype appear to modulate spinal actions.

The role of fluorine substitution in the structure-activity relationships (SAR) of classical cannabinoids

A facile synthesis of 1-fluoro-1-deoxy-Delta(8)-THC analogs with side chains seven carbons in length, in the alkane/ene/yne- series (6, 5, and 4), was achieved from 1-fluoro-3,5-dimethoxybenzene (1). In vitro studies show that substitution by a fluorine has a significant detrimental effect on CB1 binding which is supported by in vivo testing. The implications of these results on the SAR of classical cannabinoids are discussed.

Soy isoflavones do not affect bone resorption in postmenopausal women: a dose-response study using a novel approach with 41Ca

INTRODUCTION

The purpose of this 3-way crossover study was to identify the effective dose of soy protein isolate enriched with isoflavones for suppressing bone resorption in postmenopausal women using a novel, rapid assessment of antibone resorbing treatments.

METHODS

Thirteen postmenopausal women (>or=6 yr since menopause) were predosed with 41Ca iv. After a 200-d baseline period, subjects were given 43 g soy protein/d that contained 0, 97.5, or 135.5 mg total isoflavones in randomized order. The soy protein isolate powder was incorporated into baked products and beverages. Each 50-d intervention phase was preceded by a 50-d pretreatment phase for comparison. Serum isoflavone levels and biochemical markers were measured at the end of each phase. Twenty-four-hour urine samples were collected approximately every 10 d during each phase for 41Ca/Ca analysis by accelerator mass spectrometry.

RESULTS

Serum isoflavone levels reflected the amount of isoflavones consumed in a dose-dependent manner. None of the isoflavone levels had a significant effect on biochemical markers of bone turnover, urinary cross-linked N teleopeptides of type I collagen and serum osteocalcin, or bone turnover as assessed by urinary 41Ca/Ca ratios.

CONCLUSIONS

Soy protein with isoflavone doses of up to 135.5 mg/d did not suppress bone resorption in postmenopausal women. This is the first efficacy trial using the novel technique of urinary 41Ca excretion from prelabeled bone.

The psychoactive plant cannabinoid, Delta9-tetrahydrocannabinol, is antagonized by Delta8- and Delta9-tetrahydrocannabivarin in mice in vivo

BACKGROUND AND PURPOSE

To follow up in vitro evidence that Delta(9)-tetrahydrocannabivarin extracted from cannabis (eDelta(9)-THCV) is a CB(1) receptor antagonist by establishing whether synthetic Delta(9)-tetrahydrocannabivarin (O-4394) and Delta(8)-tetrahydrocannabivarin (O-4395) behave as CB(1) antagonists in vivo.

EXPERIMENTAL APPROACH

O-4394 and O-4395 were compared with eDelta(9)-THCV as displacers of [(3)H]-CP55940 from specific CB(1) binding sites on mouse brain membranes and as antagonists of CP55940 in [(35)S]GTPgammaS binding assays performed with mouse brain membranes and of R-(+)-WIN55212 in mouse isolated vasa deferentia. Their ability to antagonize in vivo effects of 3 or 10 mg kg(-1) (i.v.) Delta(9)-tetrahydrocannabinol in mice was then investigated.

KEY RESULTS

O-4394 and O-4395 exhibited similar potencies to eDelta(9)-THCV as displacers of [(3)H]-CP55940 (K (i)=46.6 and 64.4 nM, respectively) and as antagonists of CP55940 in the [(35)S]GTPgammaS binding assay (apparent K (B)=82.1 and 125.9 nM, respectively) and R-(+)-WIN55212 in the vas deferens (apparent K (B)=4.8 and 3.9 nM respectively). At i.v. doses of 0.1, 0.3, 1.0 and/or 3 mg kg(-1) O-4394 and O-4395 attenuated Delta(9)-tetrahydrocannabinol-induced anti-nociception (tail-flick test) and hypothermia (rectal temperature). O-4395 but not O-4394 also antagonized Delta(9)-tetrahydrocannabinol-induced ring immobility. By themselves, O-4395 and O-4394 induced ring immobility at 3 or 10 mg kg(-1) (i.v.) and antinociception at doses above 10 mg kg(-1) (i.v.). O-4395 also induced hypothermia at 3 mg kg(-1) (i.v.) and above.

CONCLUSIONS AND IMPLICATIONS

O-4394 and O-4395 exhibit similar in vitro potencies to eDelta(9)-THCV as CB(1) receptor ligands and as antagonists of cannabinoid receptor agonists and can antagonize Delta(9)-tetrahydrocannabinol in vivo.

Development of pharmacoresistance to benzodiazepines but not cannabinoids in the hippocampal neuronal culture model of status epilepticus

Status epilepticus (SE) is a life-threatening neurological disorder associated with a significant morbidity and mortality. Benzodiazepines are the initial drugs of choice for the treatment of SE. Despite aggressive treatment, over 40% of SE cases are refractory to the initial treatment with two or more medications. It would be a major advance in the clinical management of SE to identify novel anticonvulsant agents that do not lose their ability to treat SE with increasing seizure duration. Cannabinoids have recently been demonstrated to regulate seizure activity in brain. However, it remains to be seen whether they develop pharmacoresistance upon prolonged SE. In this study, we used low Mg(2+) to induce SE in hippocampal neuronal cultures and in agreement with animal models and human SE confirm the development of resistance to benzodiazepine with increasing durations of SE. Thus, lorazepam (1 microM) was effective in blocking low Mg(2+) induced high-frequency spiking for up to 30 min into SE. However, by 1 h and 2 h of SE onset it was only 10-15% effective in suppressing SE. In contrast, the cannabinoid type-1 (CB1) receptor agonist, WIN 55,212-2 (1 microM) in a CB1 receptor-dependent manner completely abolished SE at all the time points tested even out to 2 h after SE onset, a condition where resistance developed to lorazepam. Thus, the use of cannabinoids in the treatment of SE may offer a unique approach to controlling SE without the development of pharmacoresistance observed with conventional treatments.

New potent and selective inhibitors of anandamide reuptake with antispastic activity in a mouse model of multiple sclerosis

We previously reported that the compound O-2093 is a selective inhibitor of the reuptake of the endocannabinoid anandamide (AEA). We have now re-examined the activity of O-2093 in vivo and synthesized four structural analogs (O-2247, O-2248, O-3246, and O-3262), whose activity was assessed in: (a) binding assays carried out with membranes from cells overexpressing the human CB(1) and CB(2) receptors; (b) assays of transient receptor potential of the vanilloid type-1 (TRPV1) channel functional activity (measurement of [Ca(2+)](i)); (c) [(14)C]AEA cellular uptake and hydrolysis assays in rat basophilic leukaemia (RBL-2H3) cells; (d) the mouse 'tetrad' tests (analgesia on a hot plate, immobility on a 'ring', rectal hypothermia and hypolocomotion in an open field); and (e) the limb spasticity test in chronic relapsing experimental allergic encephalomyelitis (CREAE) mice, a model of multiple sclerosis (MS). O-2093, either synthesized by us or commercially available, was inactive in the 'tetrad' up to a 20 mg kg(-1) dose (i.v.). Like O-2093, the other four compounds exhibited low affinity in CB(1) (K(i) from 1.3 to >10 microM) and CB(2) binding assays (1.3<K(i)< 8 microM), low potency and efficacy in a TRPV1 functional assay (EC(50)>10 microM), very low potency as fatty acid amide hydrolase (FAAH) inhibitors (IC(50)>25 microM) and were inactive in the 'tetrad' up to a 30 mg kg(-1) dose (i.v.). While O-2247 and O-2248 were poor inhibitors of [(14)C]AEA cellular uptake (IC(50)>40 microM), O-3246 and O-3262 were quite potent in this assay. O-3246, which exhibits only a very subtle structural difference with O-2093, is the most potent inhibitor of AEA uptake reported in vitro under our experimental conditions (IC(50)=1.4 microM) and is 12-fold more potent than O-2093. When injected intravenously O-3246 and O-3262, again like O-2093 and unlike O-2247 and O-2248, significantly inhibited limb spasticity in mice with CREAE. These data confirm the potential utility of selective AEA uptake inhibitors as anti-spasticity drugs in MS and, given the very subtle chemical differences between potent and weak inhibitors of uptake, support further the existence of a specific mechanism for this process.

RhoA, encoding a Rho GTPase, is associated with smoking initiation

We used microarray analysis of acute nicotine responses in mouse brain to choose rationale candidates for human association studies on tobacco smoking and nicotine dependence (ND). Microarray studies on the time-course of acute response to nicotine in mouse brain identified 95 genes regulated in ventral tegmental area. Among these, 30 genes were part of a gene network, with functions relevant to neural plasticity. On this basis and their known roles in drug abuse or synaptic plasticity, we chose the genes RhoA and Ywhag as candidates for human association studies. A synteny search identified human orthologs and we investigated their role in tobacco smoking and ND in a human case-control association study. We genotyped five and three single nucleotide polymorphisms from the RhoA and Ywhag genes, respectively. Both single marker and haplotype analyses were negative for the Ywhag gene. For the RhoA gene, rs2878298 showed highly significant genotypic association with both smoking initiation (SI) and ND (P = 0.00005 for SI and P = 0.0007 for ND). In the allelic analyses, rs2878298 was only significant for SI. In the multimarker haplotype analyses, significant association with SI was found for the RhoA gene (empirical global P values ranged from 9 x 10(-5) to 10(-5)). In all multimarker combinations analyzed, with or without inclusion of the single most significant marker rs2878298, identical risk and protective haplotypes were identified. Our results indicated that the RhoA gene is likely involved in initiation of tobacco smoking and ND. Replication and future model system studies will be needed to validate the role of RhoA gene in SI and ND.