The current study examined whether adolescent rats are more vulnerable than adult rats to the lasting adverse effects of cannabinoid exposure on brain and behavior. Male Wistar rats were repeatedly exposed to D-9-tetrahydrocannabinol (D 9 -THC, 5 mg/kg i.p.) in a place-conditioning paradigm during either the adolescent (post-natal day 28 + ) or adult (post-natal day 60 + ) developmental stages. Adult rats avoided a D 9 -THC-paired environment after either four or eight pairings and this avoidance persisted for at least 16 days following the final D 9 -THC injection. In contrast, adolescent rats showed no significant place aversion. Adult D 9 -THC-treated rats produced more vocalizations than adolescent rats when handled during the intoxicated state, also suggesting greater drug-induced aversion. After a 10-15 day washout, both adult and adolescent D 9 -THC pretreated rats showed decreased social interaction, while only D 9 -THC pretreated adolescent rats showed significantly impaired object recognition memory. Seventeen days following their last D 9 -THC injection, rats were euthanased and hippocampal tissue processed using two-dimensional gel electrophoresis proteomics. There was no evidence of residual D 9 -THC being present in blood at this time. Proteomic analysis uncovered 27 proteins, many involved in regulating oxidative stress/mitochondrial functioning and cytoarchitecture, which were differentially expressed in adolescent D 9 -THC pretreated rats relative to adolescent controls. In adults, only 10 hippocampal proteins were differentially expressed in D 9 -THC compared to vehicle-pretreated controls. Overall these findings suggest that adolescent rats find repeated D 9 -THC exposure less aversive than adults, but that cannabinoid exposure causes greater lasting memory deficits and hippocampal alterations in adolescent than adult rats.

No abstract

No abstract

A 6-year-old dog, a 4-year-old dog and three 7-week-old puppies were diagnosed with thiamine deficiency caused by feeding sulphite treated meat. The 6-year-old dog presented with a history of inappetence, weight loss and vomiting that rapidly progressed to signs of multifocal intracranial disease including mental dullness, paresis, seizures, spontaneous nystagmus and strabismus. Thiamine pyrophosphate effect was elevated at 58% and magnetic resonance imaging revealed bilaterally symmetrical hyperintensity of the caudate nucleus and rostral colliculi. The dog recovered with thiamine supplementation. The 4-year-old dog and three 7-week-old puppies also presented with rapidly progressive multifocal central nervous system signs including ataxia, paresis, increased muscle tone, seizures, nystagmus and exophthalmos. The 4-year-old dog made a rapid recovery with thiamine supplementation. Euthanasia and necropsy of a puppy revealed malacia of multiple brainstem nuclei and oedema of the cerebral cortex. These findings were consistent with thiamine deficiency.

Use of the drug 3,4-methylenedioxymethamphetamine (MDMA, 'Ecstasy') can have long-term adverse effects on emotion in both humans and laboratory animals. The present study examined whether chronic treatment with the antidepressant drug fluoxetine could reverse such effects. Male Wistar rats were briefly exposed to MDMA (4 Â 5 mg/kg over 4 h) or vehicle on 2 consecutive days. Approximately 9-12 weeks later, half of the rats received a dose of approximately 6 mg/kg/day fluoxetine in their drinking water for a 5-week period. Fluoxetine administration reduced fluid intake and body weight in MDMA and vehicle pretreated rats. After several weeks of fluoxetine treatment, rats were assessed on the social interaction test, the emergence test of anxiety and the forced swim model of depression. MDMA pretreated rats showed reduced social interaction, increased anxiety on the emergence test, and increased immobility and decreased active responses in the forced swim test. Fluoxetine treatment reversed MDMA-induced anxiety in the emergence test and depressive-like effects in the forced swim test, yet exhibited no effects on the social interaction test. MDMA pretreated rats had decreased 5-HT and 5-HIAA levels in limbic and cortical regions, and decreased density of serotonin transporter sites in the cortex. Fluoxetine treatment did not greatly affect 5-HT levels in MDMA pretreated rats, but significantly decreased 5-HIAA levels in all brain sites examined. Postmortem blood serum levels of fluoxetine and norfluoxetine did not differ in MDMA and vehicle pretreated rats. These results indicate that fluoxetine may provide a treatment option for some of the deleterious long-term effects resulting from MDMA exposure.

The popular drug 3,4 methylenedioxymethamphetamine (MDMA, "Ecstasy", "the Love Drug") produces feelings of love and closeness in humans and induces analogous prosocial and antiaggressive effects in laboratory animals. Here we examined the specific brain regions that may be involved in these prosocial effects. Male Wistar rats were pretreated with a moderate dose of MDMA (5 mg/kg) or vehicle and then either kept alone in a familiar test chamber for 60 min (groups MDMA-ALONE and VEHICLE-ALONE) or allowed to engage in social interaction in the familiar test chamber with an unfamiliar same-sex conspecific for 60 min (groups MDMA-SOCIAL and VEHICLE-SOCIAL). Rats in the MDMA-SOCIAL group showed much greater overall social interaction than rats in the VEHICLE-SOCIAL group, with microanalysis revealing increased general investigation of other rats but decreased anogenital sniffing. Analysis of neural activation across 39 brain regions using Fos immunohistochemistry showed the following results: (1) VEHICLE-SOCIAL and VEHICLE-ALONE groups did not differ in Fos expression, indicating that a social context per se did not affect Fos expression, (2) MDMA-treated groups showed significantly increased Fos expression relative to VEHICLE treated groups in 30 brain regions, (3) the MDMA-SOCIAL group showed augmented Fos expression relative to the MDMA-ALONE group in six brain regions including the caudate-putamen (medial), medial preoptic area, paraventricular thalamic nucleus, central amygdala, ventromedial hypothalamic nucleus, and the medial amygdala (posterodorsal), and (4) the MDMA-SOCIAL group (but not the MDMA-ALONE group) showed augmented Fos expression relative to the VEHICLE groups in the nucleus accumbens, ventral tegmental area and periaqueductal grey. These results indicate that a moderate dose of MDMA given in a social context causes considerably greater brain activation than the same dose given to solitary rats. This activation involves specific neural circuits that are known to regulate affiliative behavior, perhaps by modulating the incentive value of social stimuli. A possible role for the neuropeptide oxytocin in mediating the prosocial effects of MDMA is discussed.

No abstract

No abstract