CB(1) receptor antagonists were among the most promising drug targets in the last decade. They have been explored and found to be effective as therapeutic agents for obesity and related cardiometabolic problems; however, use of rimonabant, the first marketed CB(1) receptor antagonist, has been suspended because of its anxiogenic and depressogenic side effects. Because some other antiobesity drugs, like dexfenfluramine or sibutramine, were also suspended, the unmet need for drugs that reduce body weight became enormous. One approach that emerged was the use of CB(1) receptor antagonists that poorly cross the blood brain barrier, the second, the development of neutral antagonists instead of inverse agonists, and the third, use of personalized medicine, namely the selection of the patient population without psychiatric side effects. In this review, we dissect the peripheral and central mechanisms involved in the effects of CB(1) receptor antagonists and argue that central mechanisms are more or less involved in most cardiometabolic therapeutic effects and thus, among patients with unsatisfactory therapeutic response to compounds with peripheral action, centrally acting antagonists may be needed. An analysis of pharmacogenetic factors may help to identify persons who are at no or low risk for psychiatric adverse effects. Here, we present the models and identify molecular mechanisms and receptors involved in the effects of stress-, anxiety- and depression-related neurocircuitries sensitive to CB(1) receptor antagonists, like the serotonergic, noradrenergic and dopaminergic systems, which are not only regulated by CB(1) receptors, but also regulate the synthesis of the endocannabinoid 2-arachidonoyl-glycerol.

In this study, we investigated the effect of chronic repeated restraint (RR) on prolactin‐releasing peptide (PrRP) expression. In the brainstem, where PrRP colocalize with norepinephrine in neurons of the A1 and A2 catecholaminergic cell groups, the expression of tyrosine hydroxylase (TH) has also been examined. In the brainstem, but not in the hypothalamus, the basal PrRP expression in female rats was higher than that in the males that was abolished by ovariectomy. RR evoked an elevation of PrRP expression in all areas investigated, with smaller reaction in the brainstems of females. There was no gender‐related difference in the RR‐evoked TH expression. Elevation of PrRP was relatively higher than elevation of TH, causing a shift in PrRP/TH ratio in the brainstem after RR. Estrogen α receptors were found in the PrRP neurons of the A1 and A2 cell groups, but not in the hypothalamus. Bilateral lesions of the hypothalamic paraventricular nucleus did not prevent RR‐evoked changes. Elevated PrRP production parallel with increased PrRP/TH ratio in A1/A2 neurons indicate that: (i) there is a clear difference in the regulation of TH and PrRP expression after RR, and (ii) among other factors this may also contribute to the changed sensitivity of the hypothalamo‐pituitary–adrenal axis during chronic stress.

ObjectivesVenlafaxine (VLX), a serotonine-noradrenaline reuptake inhibitor, is one of the most commonly used antidepressant drugs in clinical practice for the treatment of major depressive disorder (MDD). Despite being more potent than its predecessors, similarly to them, the therapeutical effect of VLX is visible only 3–4 weeks after the beginning of treatment. Furthermore, recent papers show that antidepressants, including also VLX, enhance the motor recovery after stroke even in non depressed persons. In the present, transcriptomic-based study we looked for changes in gene expressions after a long-term VLX administration.MethodsOsmotic minipumps were implanted subcutaneously into Dark Agouti rats providing a continuous (40 mg/kg/day) VLX delivery for three weeks. Frontal regions of the cerebral cortex were isolated and analyzed using Illumina bead arrays to detect genes showing significant chances in expression. Gene set enrichment analysis was performed to identify specific regulatory networks significantly affected by long term VLX treatment.ResultsChronic VLX administration may have an effect on neurotransmitter release via the regulation of genes involved in vesicular exocytosis and receptor endocytosis (such as Kif proteins, Myo5a, Sv2b, Syn2 or Synj2). Simultaneously, VLX activated the expression of genes involved in neurotrophic signaling (Ntrk2, Ntrk3), glutamatergic transmission (Gria3, Grin2b and Grin2a), neuroplasticity (Camk2g/b, Cd47), synaptogenesis (Epha5a, Gad2) and cognitive processes (Clstn2). Interestingly, VLX increased the expression of genes involved in mitochondrial antioxidant activity (Bcl2 and Prdx1). Additionally, VLX administration also modulated genes related to insulin signaling pathway (Negr1, Ppp3r1, Slc2a4 and Enpp1), a mechanism that has recently been linked to neuroprotection, learning and memory.ConclusionsOur results strongly suggest that chronic VLX treatment improves functional reorganization and brain plasticity by influencing gene expression in regulatory networks of motor cortical areas. These results are consonant with the synaptic (network) hypothesis of depression and antidepressant-induced motor recovery after stroke.

Prolonged neurotoxicity of the recreational drug, MDMA (3,4-methylenedioxymethamphetamine) on serotoninergic axon terminals has been suggested. The effect of a single (15 mg/kg) dose of intraperitoneally administered MDMA on serotoninergic fibre density, defined by tryptophan hydroxylase (TpH) and serotonin transporter (5-HTT) immunoreactivity, has been evaluated in the spinal cord and brain areas in Dark Agouti rats, 7 and 180 days after MDMA applications. Immunostaining for amyloid precursor protein (APP) has been performed to examine possible defects of the fast axonal transport, and 5-HTT mRNA expressions were quantified in neurones of medullary raphe nuclei. Seven days after MDMA treatment, a substantial decrease in the density of TpH-immunoreactive fibres was detectable in the frontal cortex, the caudate-putamen, the CA1 region of the hippocampus, and marked decreases were found in the spinal cord. These changes in TpH density showed a high correlation with 5-HTT densities. In contrast, APP-immunoreactive axonal bulbs were not detected in any of the brain regions studied. Seven days after MDMA administrations, significantly elevated 5-HTT mRNA expressions were found in the raphe pallidus and obscurus. Our results suggest that a single dose of MDMA elicits widespread depletion of TpH and 5-HTT immunoreactivity in serotoninergic axons without morphological sign of the blockage of the fast anterograde axonal transport. Our results do not support the notion of MDMA-induced axotomy of serotoninergic neurones. The up-regulation of 5-HTT mRNA expressions 1 week after MDMA injections might indicate the potential recovery of the serotonin system.

The recreational drug ecstasy [3,4-methylenedioxymethamphetamine (MDMA)], has been found to selectively damage brain serotonin neurons in experimental animals, and probably in human MDMA users, but detailed morphometric analyses and parallel functional measures during damage and recovery are missing. Since there is evidence that serotonin regulates sleep, we have compared serotonergic markers parallel with detailed analysis of sleep patterns at three time-points within 180 d after a single dose of 15 mg/kg MDMA in male Dark Agouti rats. At 7 d and 21 d after MDMA treatment, significant(30-40%), widespread reductions in serotonin transporter (5-HTT) density were detected in the cerebral cortex, hippocampus, most parts of the hypothalamus, and some of the brainstem nuclei. With the exception of the hippocampus, general recovery was observed in the brain 180 d after treatment. Transient increases followed by decreases were detected in 5-HTT mRNA expression of dorsal and median raphe nuclei at 7 d and 21 d after the treatment. Significant reductions in rapid eye movement (REM) sleep latency, increases in delta power spectra in non-rapid eye movement sleep and increased fragmentation of sleep were also detected, but all these alterations disappeared by the 180th day. The present data provide evidence for long-term, albeit, except for the hippocampus, transient changes in the terminal and cellular regions of the serotonergic system after this drug. Reduced REM latency and increased sleep fragmentation are the most characteristic alterations of sleep consistently described in depression using EEG sleep polygraphy.

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Acutely, 3,4,-methylenedioxymethamphetamine (MDMA) induces cerebrovascular dysfunction [Quate et al., (2004)Psychopharmacol., 173, 287-295]. In the longer term the same single dose results in depletion of 5-hydroxytrptamine (5-HT) nerve terminals. In this study we examined the cerebrovascular consequences of this persistent neurodegeneration, and the acute effects of subsequent MDMA exposure, upon the relationship that normally exists between local cerebral blood flow (LCBF) and local cerebral glucose utilization (LCMRglu). Dark agouti (DA) rats were pre-treated with 15 mg/kg i.p. MDMA or saline. Three weeks later, rats from each pre-treatment group were treated with an acute dose of MDMA (15 mg/kg i.p.) or saline. Quantitative autoradiographic imaging was used to measure LCBF or LCMRglu with [(14)C]-iodoantipyrine and [(14)C]-2-deoxyglucose, respectively. Serotonergic terminal depletion was assessed using radioligand binding with [(3)H]-paroxetine and immunohistochemistry. Three weeks after MDMA pre-treatment there were significant reductions in densities of 5-HT transporter (SERT)-positive fibres (-46%) and [(3)H]-paroxetine binding (-47%). In animals pre-treated with MDMA there were widespread significant decreases in LCMRglu, but no change in LCBF indicating a persistent loss of cerebrovascular constrictor tone. In both pre-treatment groups, acute MDMA produced significant increases in LCMRglu, while LCBF was significantly decreased. In 50% of MDMA-pre-treated rats, random areas of focal hyperaemia indicated a loss of autoregulatory capacity in response to MDMA-induced hypertension. These results suggest that cerebrovascular regulatory dysfunction resulting from acute exposure to MDMA is not diminished by previous exposure, despite a significant depletion in 5-HT terminals. However, there may be a sub-population, or individual circumstances, in which this dysfunction develops into a condition that might predispose to stroke.

CB(1) receptor antagonists were among the most promising drug targets in the last decade. They have been explored and found to be effective as therapeutic agents for obesity and related cardiometabolic problems; however, use of rimonabant, the first marketed CB(1) receptor antagonist, has been suspended because of its anxiogenic and depressogenic side effects. Because some other antiobesity drugs, like dexfenfluramine or sibutramine, were also suspended, the unmet need for drugs that reduce body weight became enormous. One approach that emerged was the use of CB(1) receptor antagonists that poorly cross the blood brain barrier, the second, the development of neutral antagonists instead of inverse agonists, and the third, use of personalized medicine, namely the selection of the patient population without psychiatric side effects. In this review, we dissect the peripheral and central mechanisms involved in the effects of CB(1) receptor antagonists and argue that central mechanisms are more or less involved in most cardiometabolic therapeutic effects and thus, among patients with unsatisfactory therapeutic response to compounds with peripheral action, centrally acting antagonists may be needed. An analysis of pharmacogenetic factors may help to identify persons who are at no or low risk for psychiatric adverse effects. Here, we present the models and identify molecular mechanisms and receptors involved in the effects of stress-, anxiety- and depression-related neurocircuitries sensitive to CB(1) receptor antagonists, like the serotonergic, noradrenergic and dopaminergic systems, which are not only regulated by CB(1) receptors, but also regulate the synthesis of the endocannabinoid 2-arachidonoyl-glycerol.