Chronic nicotine alters cannabinoid-mediated locomotor activity and receptor density in periadolescent but not adult male rats

A significant number of youths use cigarettes, and more than half of the youths who smoke daily also use illicit drugs. The focus of these studies is on how exposure to nicotine affects subsequent responses to both nicotine and cannabinoids in adolescents compared with adults. We have shown previously that chronic treatment with nicotine produces sensitization to its locomotor-activating effects in female and adult rats but not male adolescent rats. To better understand the effects of nicotine on adolescent and adult rats, rats were injected with nicotine or saline for 7 days and, on day 8, either challenged with delta-9-tetrahydrocannabinol (Delta 9-THC) or the cannabinoid agonist CP 55,940 and tested for locomotor activity, or the brains were removed for quantitative autoradiography studies of the cannabinoid(1) receptor. A separate group of rats was treated with nicotine plus the cannabinoid antagonist AM 251 and then challenged with CP 55,940. In adolescent male rats, nicotine administration led to sensitization to the locomotor-decreasing effects of both Delta 9-THC and CP 55,940, but in adult male rats, the response to either drug was unchanged compared to controls. The effect of nicotine on CP 55,940-mediated locomotor activity was blocked by co-administration of AM 251 with the nicotine. Further, cannabinoid receptor density was increased in the prelimbic prefrontal cortex, ventral tegmental area, and select regions of the hippocampus in adolescent male rats pretreated with nicotine compared to vehicle-treated controls. There were no significant changes in cannabinoid receptor binding, however, in any of the brain regions examined in adult males pretreated with nicotine. The prelimbic prefrontal cortex and the hippocampus have been shown previously to be involved in stimulant reinforcement; thus it is possible that these changes contribute to the unique behavioral effects of chronic nicotine and subsequent drug administration in adolescents compared with adults.

Synthesis and CB1 cannabinoid receptor affinity of 4-alkoxycarbonyl-1,5-diaryl-1,2,3-triazoles

A series of 4-alkoxycarbonyl-1,5-diaryl-1,2,3-triazoles were synthesized regioselectively using click chemistry and evaluated at CB1 cannabinoid receptors. The n-propyl ester 11 (K(i)=4.6 nM) and phenyl ester 14 (K(i)=11 nM) exhibited the most potent affinity of the series.

Sensitivity to cocaine conditioned reward depends on sex and age

Human and animal laboratory studies show that females and males respond differently to drugs and that drug administration during adolescence leads to different behavioral effects than during adulthood. Adult female rats are more sensitive to the behavioral effects of cocaine than adult males, but it is not known if the same effect of sex exists during adolescence. In the present study, sensitivity to the conditioned reward of cocaine was evaluated using a conditioned place preference (CPP) paradigm where adolescent (PND 34) and adult (PND 66) male and female rats were trained and tested for the development of CPP to multiple doses of cocaine. Female rats developed CPP at lower doses than males, regardless of age. In addition, adolescent male and female rats established a CPP at lower doses of cocaine than adult male and female rats, respectively. Thus, both age and sex altered cocaine conditioned reward with the order of sensitivity being adolescent females > adult females > adolescent males > adult males. These data show that adolescents are more sensitive to the conditioned rewarding properties of cocaine than adults and that females respond to lower doses of cocaine compared to males regardless of age.

Chronic cocaine produces decreases in N/OFQ peptide levels in select rat brain regions

The interaction of opioids and stimulants is well established; however, the mechanisms that underlie the role that opioid receptors play in psychostimulant action are not. Nociceptin/orphaninFQ (N/OFQ), the endogenous agonist at NOP receptors, attenuates the behavioral effects of cocaine. The effects of cocaine on N/OFQ were examined in rats using immunoautoradiographic and RIA techniques. Chronic administration of cocaine decreased N/OFQ in medial regions of the caudate putamen, the nucleus accumbens shell, and the substantia nigra. These studies show that N/OFQ levels are altered by treatment with cocaine. Furthermore, the changes in N/OFQ parallel those seen for kappa-opioid receptors, suggesting that the interactions between cocaine and these systems might be similar.

Effect of MDMA (ecstasy) on activity and cocaine conditioned place preference in adult and adolescent rats

MDMA (ecstasy) is a drug commonly used in adolescence, and many users of MDMA also use other illicit drugs. It is not known whether MDMA during adolescence alters subsequent responses to cocaine differently than in adults. This study examined the effects of MDMA in adolescent and adult rats on cocaine conditioned reward. At the start of these experiments, adolescent rats were at postnatal day (PND) 33 and adult rats at PND 60. Each rat was treated for 7 days with MDMA (2 or 5 mg/kg/day or vehicle) and locomotor activity was measured. Five days later cocaine conditioned place preference (CPP) was begun. Rats were trained for 3 days, in the morning with saline and in the afternoon with 10 mg/kg cocaine in 30 min sessions, and tested on the fourth day. MDMA stimulated activity in both age groups, but with a greater effect in the adult rats. Sensitization to the locomotor-stimulant effects of the lower dose of MDMA occurred in adult rats and in both groups to the higher dose. Cocaine did not produce a CPP in vehicle-treated adolescent rats, but a significant CPP was observed subsequent to treatment with MDMA. In contrast, cocaine-induced CPP was diminished after MDMA in adult rats. These effects were still evident 2 weeks later upon retest. Thus, under the present conditions, MDMA increased cocaine conditioned reward in adolescent and decreased it in adult rats. These findings suggest that exposure to MDMA during this critical developmental period may carry a greater risk than during adulthood and that male adolescents may be particularly vulnerable to the risk of stimulant abuse after use of MDMA.

Substance misuse in first-episode psychosis: 15-month prospective follow-up study

BACKGROUND

Well-designed prospective studies of substance misuse in first-episode psychosis can improve our understanding of the risks associated with comorbid substance misuse and psychosis.

AIMS

To examine the potential effects of substance misuse on in-patient admission and remission and relapse of positive symptoms in first-episode psychosis.

METHOD

The study was a prospective 15-month follow-up investigation of 103 patients with first-episode psychosis recruited from three mental health services.

RESULTS

Substance misuse was independently associated with increased risk of in-patient admission, relapse of positive symptoms and shorter time to relapse of positive symptoms after controlling for potential confounding factors. Substance misuse was not associated with remission or time to remission of positive symptoms. Heavy substance misuse was associated with increased risk of in-patient admission, relapse and shorter time to relapse.

CONCLUSIONS

Substance misuse is an independent risk factor for a problematic recovery from first-episode psychosis.

Synthesis of dopamine transporter selective 3-diarylmethoxymethyl-8-arylalkyl-8-azabicyclo[3.2.1]octane derivatives

A series of diarylmethoxymethyltropane-GBR hybrid analogues with all three possible stereochemical orientations at C3 were synthesized and evaluated at dopamine and serotonin transporters. The 3alpha derivatives were found to be the most potent compounds with the 3alpha-di(4-fluorophenyl)methoxymethyl-8-(3-phenylpropyl)-8-azabicyclo[3.2.1]octane 15b (Ki = 5 nM) being the most potent compound of the series. The corresponding 3-di(4-fluorophenyl)-methoxymethyl-8-(3-phenylpropyl)-8-azabicyclo[3.2.1]oct-2-ene 12b (Ki = 12 nM) was slightly less potent than the 3alpha-analogue, while the 3beta-di(4-fluorophenyl)methoxymethyl-8-(3-phenylpropyl)-8-azabicyclo[3.2.1]octane 23b (Ki = 78 nM) exhibited only modest affinity for the dopamine transporter. Only the 3alpha-analogue 15b (SERT/DAT = 48) exhibited higher SERT/DAT selectivity than GBR 12909. These results indicate that the dopamine transporter can tolerate some variability in proximity of the benzhydryl ether to the basic nitrogen atom of the tropane without loss in potency. In addition, the structure-activity data for these tropane-GBR 12909 hybrid analogues support previous findings that the stereochemical and conformational effects imparted by unsaturation at C3 are important for dopamine transporter selectivity over the serotonin transporter.

Structure-activity studies of 3'-4'-dichloro-meperidine analogues at dopamine and serotonin transporters

The structure-activity relationships of 3',4'-dichloro-meperidine were investigated at dopamine (DAT) and serotonin transporters (SERT). Large ester substituents and lipophilic groups at the 4-position favored molecular recognition at the SERT. The benzyl ester of 3',4'-dichloro-meperidine exhibited high potency and high selectivity for the SERT (DAT/SERT=760). Chemical modification of the ester group and N-substitution generally led to compounds with decreased DAT affinity. Only small esters and alkyl groups were tolerated at the 4-position of the meperidine ring system by the DAT. Overall, the meperidine analogues were generally more selective for the SERT than for the DAT.

The impact of substance use disorders on clinical outcome in 643 patients with first-episode psychosis

OBJECTIVE

Studies investigating the impact of comorbid substance use disorders (SUD) in psychosis have tended to focus on cross-sectional data, with few studies examining the effects of substance use course on clinical outcome. The main aim of the present study was to assess the impact of baseline SUD and course of SUD on remission of positive symptoms.

METHOD

The Early Psychosis Prevention and Intervention Centre admitted 786 first-episode psychosis (FEP) patients between 1998 and 2000. Data on SUD and clinical outcome were collected from patients' medical records (MR) of 643 patients who met inclusion criteria.

RESULTS

Lifetime prevalence of SUD was 74%, with 62% having a SUD at baseline. This reduced to 36% in those patients who completed 18 months of treatment at the EPPIC program. A Cox regression analysis indicated that a decrease or cessation of substance use significantly increased the probability of remission, whilst persistent SUD substantially reduced the likelihood. In addition, patients who reduced use appeared to have better outcomes at 18 months than those patients who had never used substances. Baseline SUD was not found to have any significant influence on symptom remission.

CONCLUSION

Patients presenting with FEP have high rates of SUD. Effective management of psychosis within a specialized service is associated with reductions in SUD over the course of treatment, although persistent substance use is associated with non-compliance, treatment drop-out and poor remission rates. As such, young people with FEP and comorbid substance use should be offered integrated treatment that addresses both disorders.

Synthesis and biological evaluation of meperidine analogues at monoamine transporters

A series of aryl-substituted meperidine analogues was synthesized, and the binding affinities were determined at the DAT, SERT, and NET as well as at mu-opioid receptors. Generally the analogues exhibited increased affinity for the DAT and SERT relative to meperidine but exhibited low binding affinity for the NET. The 2-naphthyl derivative 7f was the most potent ligand at the SERT (K(i) = 0.0072 muM) and was the most selective ligand for the SERT over the DAT (DAT/SERT = 158) and mu-opioid receptors (mu/SERT = 281). The 3,4-dichlorophenyl derivative 7e was the most potent ligand at the DAT (K(i) = 0.125 muM) and was the most selective ligand for the DAT over mu-opioid receptors (mu/DAT = 16.3) but remained slightly more selective for the SERT over the DAT(DAT/SERT = 6.68). Three compounds, the 3,4-dichlorophenyl derivative 7e and the 2-naphthyl analogues 6f and 7f, were identified that were more potent at the DAT than meperidine and that exhibited well-defined biphasic dopamine uptake inhibition similar to meperidine. However, none of the analogues tested produced locomotor effects or substituted for cocaine in drug discrimination studies, suggesting that the mu-opioid effects of these analogues may contribute to the poor efficacy observed in vivo.

Neurochemical alterations produced by daily nicotine exposure in periadolescent vs. adult male rats

Chronic treatment with nicotine differentially alters behavior in adolescent rats compared to adult rats. It is not known, however, whether the effects of nicotine on the neurochemical pathways with which it interacts differ in adolescents vs. adults. In the current study, the effects of a 7-day treatment with nicotine on nicotinic, dopaminergic, and serotonergic neurochemistry were examined in the caudate putamen and nucleus accumbens in periadolescent vs. adult male rats. Nicotine treatment increased dopamine transporter densities and decreased serotonin transporter densities in periadolescent rats. There was no change in nicotinic acetylcholine receptor densities or dopamine D1 or D2 receptor densities in nicotine-pretreated periadolescent rats. In adult rats pretreated with nicotine, there was an increase in nicotinic acetylcholine densities, but no change in dopamine transporter, dopamine D1 or D2 receptor, or serotonin transporter densities. Overall, these findings show that periadolescent rats have neurochemical adaptations to nicotine different from adult rats. These alterations may explain, at least in part, the differential behavioral effects of chronic nicotine in adult and adolescent male rats.

Synthesis and nicotinic acetylcholine receptor binding affinities of 2- and 3-isoxazolyl-8-azabicyclo[3.2.1]octanes

A series of epiboxidine homologues, 2- and 3-isoxazole substituted 8-azabicyclo[3.2.1]octane derivatives was synthesized and evaluated as potential ligands for neuronal nicotinic acetylcholine receptors in [(3)H]cytisine labeled rat brain. The 2beta-isoxazolyl-8-azabicyclo[3.2.1]octane 9b (K(i)=3 nM) was the most potent compound of the series with a binding affinity twice that of nicotine. The 3beta-isoxazolyl-8-azabicyclo[3.2.1]octane 15b (K(i)=148 nM) exhibited moderate affinity while the corresponding 2alpha- and 3alpha-isomers exhibited micromolar binding affinity.

Inactivation of viruses infecting ectothermic animals by amphibian and piscine antimicrobial peptides

The ability of five purified amphibian antimicrobial peptides (dermaseptin-1, temporin A, magainin I, and II, PGLa), crude peptide fractions isolated from the skin of Rana pipiens and R. catesbeiana, and four antimicrobial peptides (AMPs) from hybrid striped bass (piscidin-1N, -1H, -2, and -3) were examined for their ability to reduce the infectivity of channel catfish virus (CCV) and frog virus 3 (FV3). All compounds, with the exception of magainin I, markedly reduced the infectivity of CCV. In contrast to CCV, FV3 was 2- to 4-fold less sensitive to these agents. Similar to an earlier study employing two other amphibian peptides, the agents used here acted rapidly and over a wide, physiologically relevant, temperature range to reduce virus infectivity. These results extend our previous findings and strongly suggest that various amphibian and piscine AMPs may play important roles in protecting fish and amphibians from pathogenic viruses.

Synthesis of dopamine transporter selective 3-[2-(diarylmethoxyethylidene)]-8-alkylaryl-8-azabicyclo[3.2.1]octanes

A series of 3-[2-(diarylmethoxyethylidene)]-8-alkylaryl-8-azabicyclo[3.2.1]octanes was synthesized and the binding affinities of the compounds were determined at the dopamine and serotonin transporters. The 8-phenylpropyl analogues 8a (K(i)=4.1 nM) and 8b (K(i)=3.7 nM) were the most potent compounds of the series with binding affinities 3 times greater than GBR-12909. In addition, 8a (SERT/DAT=327) was over 300-fold more selective for the dopamine transporter than the serotonin transporter.

Synthesis and dopamine transporter binding affinities of 3alpha-benzyl-8-(diarylmethoxyethyl)-8-azabicyclo[3.2.1]octanes

A series of 3alpha-benzyl-8-(diarylmethoxyethyl)-8-azabicyclo[3.2.1]octanes was synthesized and the binding affinities of the compounds were determined at the dopamine transporter. The unsubstituted analogue 7b (K(i)=98nM) was the most potent compound of the series with binding affinity three-times greater than cocaine and only 5-fold less than GBR-12909. The structure-activity data for 7a-f suggests that these compounds may be binding at the dopamine transporter in a similar fashion to GBR 12909.

Synthesis and biological evaluation at nicotinic acetylcholine receptors of N-arylalkyl- and N-aryl-7-azabicyclo[2.2.1]heptanes

A new series of N-arylalkyl-substituted 7-azabicyclo[2.2.1]heptanes and N-aryl-substituted 7-azabicyclo[2.2.1]heptanes were synthesized and evaluated as potential ligands for neuronal nicotinic acetylcholine receptors. The in vitro binding affinities (K(i)) of the 7-azabicyclo[2.2.1]heptane derivatives were measured by inhibition of [(3)H]cytisine binding to rat brain tissue. The most potent ligand of the series was found to be N-(3-pyridylmethyl)-7-azabicyclo[2.2.1]heptane (5b, K(i) = 98 nM). The chloro analogue (5a, K(i) = 245 nM) 5a and epibatidine (1) produced dose-dependent analgesia in both hotplate and tail-flick tests when administered subcutaneously. However, when compounds 1 and 5a,b were administered intrathecally, all produced analgesia in the tail-flick test but only 5a produced analgesia in the hotplate test.