Differential behavioural and neurochemical outcomes from chronic paroxetine treatment in adolescent and adult rats: a model of adverse antidepressant effects in human adolescents?

Selective serotonin reuptake inhibitor use is associated with increased risk of suicidal ideation in adolescent humans, yet the neuropharmacological basis of this phenomenon is unknown. Consequently, we examined the behavioural and neurochemical effects of chronic paroxetine (PRX) treatment in adult and adolescent rats. Rats received PRX in their drinking water (target dose 10 mg/kg) for 22 d, during which time they were assessed for depression- and anxiety-like behaviours. Subsequent ex-vivo analyses examined serum PRX concentrations, striatal neurotransmitter content, and regional serotonin and dopamine transporter (SERT, DAT) binding density. After 11–12 d treatment, PRX-treated adolescent rats showed a significant inhibition of social interaction while adults were unaffected. After 19–20 d treatment, adolescents failed to show an antidepressant-like effect of PRX treatment on the forced swim test (FST), while PRX-treated adults showed a typical decrease in immobility and increase in swimming. Two PRX-treated adolescents died unexpectedly after the FST suggesting a compromised response to physical stress. Despite their greater apparent adverse reaction to the drug, adolescents had significantly lower plasma PRX than adults at day 22 of treatment. Chronic PRX treatment had similar effects in adults and adolescents on striatal 5-HT (unchanged relative to controls) and 5-HIAA levels (decreased), while markers of dopaminergic function (DOPAC, HVA, DA turnover) were increased in adults only. SERT density was up-regulated in the amygdala in PRX-treated adolescents only while DAT density in the nucleus accumbens was down-regulated only in PRX-treated adults. These data suggest that the immature rat brain responds differently to PRX and that this might be of use in modelling the atypical response of human adolescents to antidepressants. The age-specific PRX-induced changes in dopaminergic markers and SERT and DAT binding provide clues as to the neural mechanisms underlying adverse PRX effects in adolescent humans. © 2011, Cambridge University Pres

Mephedrone in adolescent rats: residual memory impairment and acute but not lasting 5-HT depletion

Mephedrone (4-methylmethcathinone, MMC) is a popular recreational drug, yet its potential harms are yet to be fully established. The current study examined the impact of single or repeated MMC exposure on various neurochemical and behavioral measures in rats. In Experiment 1 male adolescent Wistar rats received single or repeated (once a day for 10 days) injections of MMC (30 mg/kg) or the comparator drug methamphetamine (METH, 2.5 mg/kg). Both MMC and METH caused robust hyperactivity in the 1 h following injection although this effect did not tend to sensitize with repeated treatment. Striatal dopamine (DA) levels were increased 1 h following either METH or MMC while striatal and hippocampal serotonin (5-HT) levels were decreased 1 h following MMC but not METH. MMC caused greater increases in 5-HT metabolism and greater reductions in DA metabolism in rats that had been previously exposed to MMC. Autoradiographic analysis showed no signs of neuroinflammation ([125I]CLINDE ligand used as a marker for translocator protein (TSPO) expression) with repeated exposure to either MMC or METH. In Experiment 2, rats received repeated MMC (7.5, 15 or 30 mg/kg once a day for 10 days) and were examined for residual behavioral effects following treatment. Repeated high (30 mg/kg) dose MMC produced impaired novel object recognition 5 weeks after drug treatment. However, no residual changes in 5-HT or DA tissue levels were observed at 7 weeks post-treatment. Overall these results show that MMC causes acute but not lasting changes in DA and 5-HT tissue concentrations. MMC can also cause long-term memory impairment. Future studies of cognitive function in MMC users are clearly warranted. © 2012 PLoS On

Caveats of chronic exogenous corticosterone treatments in adolescent rats and effects on anxiety-like and depressive behavior and hypothalamic-pituitary-adrenal (HPA) axis function

<p>Abstract</p> <p>Background</p> <p>Administration of exogenous corticosterone is an effective preclinical model of depression, but its use has involved primarily adult rodents. Using two different procedures of administration drawn from the literature, we explored the possibility of exogenous corticosterone models in adolescence, a time of heightened risk for mood disorders in humans.</p> <p>Methods</p> <p>In experiment 1, rats were injected with 40 mg/kg corticosterone or vehicle from postnatal days 30 to 45 and compared with no injection controls on behavior in the elevated plus maze (EPM) and the forced swim test (FST). Experiment 2 consisted of three treatments administered to rats from postnatal days 30 to 45 or as adults (days 70 to 85): either corticosterone (400 μg/ml) administered in the drinking water along with 2.5% ethanol, 2.5% ethanol or water only. In addition to testing on EPM, blood samples after the FST were obtained to measure plasma corticosterone. Analysis of variance (ANOVA) and alpha level of <it>P </it>< 0.05 were used to determine statistical significance.</p> <p>Results</p> <p>In experiment 1, corticosterone treatment of adolescent rats increased anxiety in the EPM and decreased immobility in the FST compared to no injection control rats. However, vehicle injected rats were similar to corticosterone injected rats, suggesting that adolescent rats may be highly vulnerable to stress of injection. In experiment 2, the intake of treated water, and thus doses delivered, differed for adolescents and adults, but there were no effects of treatment on behavior in the EPM or FST. Rats that had ingested corticosterone had reduced corticosterone release after the FST. Ethanol vehicle also affected corticosterone release compared to those ingesting water only, but differently for adolescents than for adults.</p> <p>Conclusions</p> <p>The results indicate that several challenges must be overcome before the exogenous corticosterone model can be used effectively in adolescents.</p

Case Report: Testicular failure possibly associated with chronic use of methylphenidate

Methylphenidate is a commonly prescribed treatment for attention deficit hyperactivity disorder (ADHD). However, little is known about its adverse effects on the male reproductive system. We report a 20-year-old male patient whose chief complaint was of delayed puberty. He spoke in a high-pitched voice and complained of lack of body hair, impaired libido, inadequate erectile function, chronic fatigue, and low energy. He had been treated with methylphenidate as an infant and had continued treatment for 17 years. On examination, the patient was lean and visibly lacked facial or body hair. He further explained that he had never been able to grow underarm or facial hair and that he was often mistakenly considered a young teenager rather than a 20-year-old. The patient’s genitalia were categorized as Tanner Stage 2. Laboratory studies confirmed low serum follicle-stimulating hormone (FSH), luteinizing hormone (LH), and testosterone levels. The patient was given exogenous testosterone supplementation with pellets and human chorionic gonadotropin to maintain testicular size. After 4 months his symptoms improved and he demonstrated signs of puberty. Our goal is to further elucidate the possible impact of methylphenidate on the male reproductive system

Mephedrone in Adolescent Rats: Residual Memory Impairment and Acute but Not Lasting 5-HT Depletion

Mephedrone (4-methylmethcathinone, MMC) is a popular recreational drug, yet its potential harms are yet to be fully established. The current study examined the impact of single or repeated MMC exposure on various neurochemical and behavioral measures in rats. In Experiment 1 male adolescent Wistar rats received single or repeated (once a day for 10 days) injections of MMC (30 mg/kg) or the comparator drug methamphetamine (METH, 2.5 mg/kg). Both MMC and METH caused robust hyperactivity in the 1 h following injection although this effect did not tend to sensitize with repeated treatment. Striatal dopamine (DA) levels were increased 1 h following either METH or MMC while striatal and hippocampal serotonin (5-HT) levels were decreased 1 h following MMC but not METH. MMC caused greater increases in 5-HT metabolism and greater reductions in DA metabolism in rats that had been previously exposed to MMC. Autoradiographic analysis showed no signs of neuroinflammation ([125I]CLINDE ligand used as a marker for translocator protein (TSPO) expression) with repeated exposure to either MMC or METH. In Experiment 2, rats received repeated MMC (7.5, 15 or 30 mg/kg once a day for 10 days) and were examined for residual behavioral effects following treatment. Repeated high (30 mg/kg) dose MMC produced impaired novel object recognition 5 weeks after drug treatment. However, no residual changes in 5-HT or DA tissue levels were observed at 7 weeks post-treatment. Overall these results show that MMC causes acute but not lasting changes in DA and 5-HT tissue concentrations. MMC can also cause long-term memory impairment. Future studies of cognitive function in MMC users are clearly warranted. © 2012 Motbey et al

Cannabidiol potentiates Δ9-tetrahydrocannabinol (THC) behavioural effects and alters THC pharmacokinetics during acute and chronic treatment in adolescent rats

Rationale The interactions between Δ9-tetrahydrocannabinol (THC) and cannabidiol (CBD) during chronic treatment, and at equivalent doses, are not well characterised in animal models. Objectives The aim of this study is to examine whether the behavioural effects of THC, and blood and brain THC levels are affected by pre-treatment with equivalent CBD doses. Methods Adolescent rats were treated with ascending daily THC doses over 21 days (1 then 3 then 10 mg/kg). Some rats were given equivalent CBD doses 20 min prior to each THC injection to allow examination of possible antagonistic effects of CBD. During dosing, rats were assessed for THC and CBD/THC effects on anxiety-like behaviour, social interaction and place conditioning. At the end of dosing, blood and brain levels of THC, and CB1 and 5- HT1A receptor binding were assessed. Results CBD potentiated an inhibition of body weight gain caused by chronic THC, andmildly augmented the anxiogenic effects, locomotor suppressant effects and decreased social interaction seen with THC. A trend towards place preference was observed in adolescent rats given CBD/THC but not those given THC alone.With both acute and chronic administration, CBD pre-treatment potentiated blood and brain THC levels, and lowered levels of THC metabolites (THC-COOH and 11-OH-THC). CBD co-administration did not alter the THC-induced decreases in CB1 receptor binding and no drug effects on 5-HT1A receptor binding were observed. Conclusions CBD can potentiate the psychoactive and physiological effects of THC in rats, most likely by delaying the metabolism and elimination of THC through an action on the CYP450 enzymes that metabolise both drugs. Keywords THC . Cannabidiol . Cannabis . Adolescent . Anxiety . Reward . Pharmacokinetic

Trends in GP prescribing of psychotropic medications among young patients aged 16-24 years: A case study analysis

Background: Current clinical guidelines recommend non-pharmacological interventions as first-line treatments for young patients aged 16-24 years with a mental health condition (MHC). However, several studies have noted increasing trends in psychotropic prescribing for this age group, especially in antidepressant prescribing. In Australia, the vast majority of psychotropic medications prescribed to young people come from the general practice setting. To assess whether Australian General Practitioners (GPs) are prescribing in accordance with clinical guideline recommendations, this study examined trends in GP prescribing of psychotropic medications to young patients aged 16-24 years. Methods: We performed a retrospective analysis of routine general practice data from 9112 patients aged 16-24 years with a MHC. Data were extracted from the Melbourne East Monash General Practice Database from 1/01/2009 to 31/12/2014. The main outcome measures included the number of consultations for patients with MHCs, psychotropic prescribing by GPs, and patient characteristics associated with the likelihood of being prescribed a psychotropic. Results: In total, 9112 out of a total of 77,466 young patients were identified as having a MHC in this study, and 11,934 psychotropic prescriptions were provided to 3967 (43.5%) of them over the study period. Antidepressants accounted for 81.4% of total psychotropic prescriptions, followed by anxiolytics (9.6%) and antipsychotics (9.0%). The number of prescriptions issued to individuals with MHCs increased over time. Women and patients aged 21-24 years had higher incidence rates for prescription than men and those aged 16-17 (IRR: 1.15, 95% CI 1.08-1.22, IRR: 1.93, 95% CI 1.750-2.11). Conclusions: Our findings demonstrate an increasing trend in GP prescribing of psychotropics to young people over the study period with higher levels of prescribing to women and those 21-24 years of age. Although GP prescribing corresponded with guideline recommendations on the whole, there were discrepancies between GP's antidepressant prescribing and guideline recommendations, reasons for which were unclear. Research is needed to investigate GPs decision-making processes underlying their prescribing, to target interventions to improve existing data in GP records to improve management, and to identify areas of further training if needed to facilitate greater concordance between clinical practice and guideline recommendations