Viloxazine Increases Extracellular Concentrations of Norepinephrine, Dopamine, and Serotonin in the Rat Prefrontal Cortex at Doses Relevant for the Treatment of Attention-Deficit/Hyperactivity Disorder.

Background: Viloxazine ER (viloxazine extended-release capsules; Qelbree®), a nonstimulant attention-deficit/hyperactivity disorder (ADHD) treatment, has known activity as a norepinephrine (NE) transporter (NET) inhibitor. In vitro studies have also shown direct pharmacological effects on specific serotonin (5-HT) receptors, but not on the serotonin transporter (SERT). An in vivo microdialysis study in rats showed viloxazine (50 mg/kg i.p.) increased extracellular 5-HT, NE, and dopamine (DA) in the prefrontal cortex (PFC), a key brain region in ADHD pathology. This study evaluated whether these effects occur at clinically relevant concentrations. Methods: Microdialysis experiments were conducted in freely-moving, Sprague-Dawley rats (males, 8 weeks). Viloxazine (1, 3, 10, 30 mg/kg) was administered intraperitoneally to establish the dose range in rats at which viloxazine plasma concentrations aligned with those of individuals with ADHD administered therapeutic doses of viloxazine ER. Concentrations of unbound viloxazine, NE, 5-HT, DA, and NE and 5-HT metabolites (3,5-dihydroxyphenylglycol [DHPG] and 5-hydroxyindoleacetic acid [5-HIAA]) were measured in PFC interstitial fluid. After identifying a therapeutically relevant dose (30 mg/kg), the experiment was repeated using 30 and 50 mg/kg viloxazine (as 50 mg/kg increased NE, 5-HT, and DA in prior studies). Results: Viloxazine unbound (free drug) plasma concentrations in rats at 30 mg/kg were comparable to free drug concentrations in individuals with ADHD taking clinically effective doses (based on validated population PK models). Viloxazine 30 mg/kg significantly increased extracellular NE, 5-HT, and DA PFC levels compared to vehicle. Concomitant decreases in DHPG, but not 5-HIAA, support the inhibitory effect of viloxazine on NET but not SERT. Conclusion: At clinically relevant concentrations, viloxazine increases PFC NE, DA, and 5-HT. Prefrontal augmentation of 5-HT does not appear to result from 5-HT reuptake inhibition but may be related to activation of 5-HT neurons. The potential therapeutic role of serotonergic effects in ADHD treatment merits further exploration.

Amitifadine, a triple monoamine re-uptake inhibitor, reduces nicotine self-administration in female rats.

A wider diversity of drug treatments to aid smoking cessation is needed to help tailor the most efficacious treatment for different types of smokers. This study was conducted to determine whether amitifadine, which inhibits re-uptake of dopamine, norepinephrine and serotonin, would decrease nicotine self-administration at doses that do not cause adverse side effects. Adult female Sprague-Dawley rats were trained to self-administer nicotine intravenous (IV) and were given acute doses of amitifadine in a repeated measures counterbalanced design. Effects of amitifadine on locomotor activity and food motivated responding were also evaluated. Chronic amitifadine effects were also examined. The 30 mg/kg amitifadine dose significantly reduced nicotine self-administration. The 5 and 10 mg/kg doses reduced nicotine self-administration during the first 15 min of the session when the greatest amount of nicotine was self-administered. The 30 mg/kg amitifadine dose, but not the lower doses caused a significant reduction in locomotor activity averaged over the one-hour session and reduced food motivated responding. The 10 mg/kg dose caused hypoactivity at the beginning of the session, but 5 mg/kg did not cause any hypoactivity. The effects of chronic amitifadine treatment (10 mg/kg) over the course of 15 sessions was also determined. Amitifadine caused a significant reduction in nicotine self-administration, which was not seen to diminish over two consecutive weeks of treatment and a week after enforced abstinence. Amitifadine significantly reduced nicotine self-administration. This prompts further research to determine if amitifadine might be an effective treatment for smoking cessation.

Antipsychotic-like effect of the muscarinic acetylcholine receptor agonist BuTAC in non-human primates.

Cholinergic, muscarinic receptor agonists exhibit functional dopamine antagonism and muscarinic receptors have been suggested as possible future targets for the treatment of schizophrenia and drug abuse. The muscarinic ligand (5R,6R)-6-(3-butylthio-1,2,5-thiadiazol-4-yl)-1-azabicyclo[3.2.1]octane (BuTAC) exhibits high affinity for muscarinic receptors with no or substantially less affinity for a large number of other receptors and binding sites, including the dopamine receptors and the dopamine transporter. In the present study, we wanted to examine the possible antipsychotic-like effects of BuTAC in primates. To this end, we investigated the effects of BuTAC on d-amphetamine-induced behaviour in antipsychotic-naive Cebus paella monkeys. Possible adverse events of BuTAC, were evaluated in the same monkeys as well as in monkeys sensitized to antipsychotic-induced extrapyramidal side effects. The present data suggests that, the muscarinic receptor ligand BuTAC exhibits antipsychotic-like behaviour in primates. The behavioural data of BuTAC as well as the new biochemical data further substantiate the rationale for the use of muscarinic M1/M2/M4-preferring receptor agonists as novel pharmacological tools in the treatment of schizophrenia.

Biopharmaceutical characterization, metabolism, and brain penetration of the triple reuptake inhibitor amitifadine.

Amitifadine (EB-1010, formerly DOV 21,947) is a serotonin-preferring triple reuptake inhibitor that is a drug candidate for major depressive disorder. We investigated several relevant biopharmaceutic and drug-like characteristics of amitifadine using in vitro methodology and additionally determined the in vivo brain to plasma ratio of the drug in rats. Amitifadine was highly plasma protein bound with over 99% of drug bound to human plasma proteins. Using Caco-2 cell lines, amitifadine was bidirectionally highly permeable and showed no evidence of active secretion. Amitifadine was metabolized slowly by human hepatocytes and the major metabolite was the lactam EB-10101. In vitro studies using human liver microsomes demonstrated that EB-10101 was formed by monoamine oxidase A (MAO-A) and a NADPHdependent enzyme, possibly a cytochrome P450 (CYP) isoform. Amitifadine was a moderate inhibitor of the human isoforms of the major drug metabolizing enzymes CYP2D6, CYP3A4, CYP2C9, and CYP2C19 (IC50 = 9 - 100 µM), but was a potent inhibitor of human CYP2B6 (IC50 = 1.8 µM). The brain to plasma ratio for amitifadine varied from 3.7 - 6.5 at various time points, indicating preferential partitioning into rat brain versus plasma. The low affinity for the major drug metabolizing CYP enzymes and metabolism by multiple pathways may reduce pharmacokinetic drug-drug interactions and effects of enzyme polymorphisms. Overall, these studies suggest that amitifadine has drug-like characteristics favorable for drug development.

A review of the abuse potential assessment of atomoxetine: a nonstimulant medication for attention-deficit/hyperactivity disorder.

RATIONALE: Treatment of attention-deficit/hyperactivity disorder (ADHD) has for many years relied on psychostimulants, particularly various formulations of amphetamines and methylphenidate. These are central nervous system stimulants and are scheduled because of their abuse potential. Atomoxetine (atomoxetine hydrochloride; Strattera®) was approved in 2002 for treatment of ADHD, and was the first nonstimulant medication approved for this disorder. It was classified as an unscheduled medication indicating a low potential for abuse. However, the abuse potential of atomoxetine has not been reviewed. OBJECTIVES: In this article, we review the evidence regarding abuse potential of atomoxetine, a selective inhibitor of the presynaptic norepinephrine transporter, which is unscheduled/unrestricted in all countries where it is approved. METHODS: Results from receptor binding, in vitro electrophysiology, in vivo microdialysis, preclinical behavioral, and human laboratory studies have been reviewed. RESULTS: Atomoxetine has no appreciable affinity for, or action at, central receptors through which drugs of abuse typically act, i.e., dopamine transporters, GABA(A) receptors, and opioid µ receptors. In behavioral experiments in rodents, atomoxetine does not increase locomotor activity, and in drug discrimination studies, its profile is similar to that of drugs without abuse potential. Atomoxetine does not serve as a reinforcer in monkey self-administration studies, and human laboratory studies suggest that atomoxetine does not induce subjective effects indicative of abuse. CONCLUSION: Neurochemical, preclinical, and early clinical studies predicted and supported a lack of abuse potential of atomoxetine, which is consistent with the clinical trial and postmarketing spontaneous event data in the past 10 years.

Muscarinic mechanisms in psychotic disorders.

Schizophrenia is a devastating disease with several broad symptom clusters and the current monoamine-based treatments do not adequately treat the disease, especially negative and cognitive symptoms. A proposed alternative approach for treating schizophrenia is through the use of compounds that activate certain muscarinic receptor subtypes, the so-called muscarinic cholinergic hypothesis theory. This theory has been revitalized with a number of recent and provocative findings including postmortem reports in schizophrenia patients showing decreased numbers of muscarinic M(1) and M(4) receptors in brain regions associated with schizophrenia as well as decreased muscarinic receptors in an in vivo imaging study. Studies with M(4) knockout mice have shown that there is a reciprocal relationship between M(4) and dopamine receptor function, and a number of muscarinic agonists have shown antidopaminergic activity in a variety of preclinical assays predictive of antipsychotic efficacy in the clinic. Furthermore, the M(1)/M(4) preferring partial agonist xanomeline has been shown to have antipsychotic-like and pro-cognitive activity in preclinical models and in clinical trials to decrease psychotic-like behaviors in Alzheimer's patients and positive, negative, and cognitive symptoms in patients with schizophrenia. Therefore, we propose that an agonist with M(1) and M(4) interactions would effectively treat core symptom clusters associated with schizophrenia. Currently, research is focused on developing subtype-selective muscarinic agonists and positive allosteric modulators that have reduced propensity for parasympathetic side-effects, but retain the therapeutic benefit observed with their less selective predecessors.

Pharmacological characterization of the norepinephrine and dopamine reuptake inhibitor EB-1020: implications for treatment of attention-deficit hyperactivity disorder.

We report on the pharmacological, behavioral, and neurochemical characterization of a novel dual norepinephrine (NE)/dopamine (DA) transporter inhibitor EB-1020 (1R,5S)-1-(naphthalen-2-yl)-3-azabicyclo[3.1.0]hexane HCl). EB-1020 preferentially inhibited monoamine reuptake in cloned cell lines transfected with human transporters with IC50 values of 6 and 38, respectively, for NE and DA transporters. In microdialysis studies, EB-1020 markedly increased NE, and DA concentrations levels in rat prefrontal cortex in vivo with peak increases of 375 and 300%, respectively with the greatest effects on NE, and also increased DA extracellular concentrations in the striatum to 400% of baseline concentrations. Behavioral studies demonstrated that EB-1020 dose-dependently decreased immobility in the mouse tail suspension test of depression to 13% of control levels, and did not stimulate locomotor activity in adult rats in the optimal dose range. EB-1020 dose-dependently inhibited locomotor hyperactivity in juvenile rats lesioned with the neurotoxin 6-hydroxydopamine (100 µg intracisternally) as neonates; a well-established animal model for attention-deficit hyperactivity disorder (ADHD). These data suggest that EB-1020 mediates its actions by stimulating NE and DA neurotransmission, which are typically impaired in ADHD.

Effects of the triple reuptake inhibitor amitifadine on extracellular levels of monoamines in rat brain regions and on locomotor activity.

Major depressive disorder is a prevalent disease, and current pharmacotherapy is considered to be inadequate. It has been hypothesized that a triple reuptake inhibitor (TRI) that activates dopamine (DA) neurotransmission in addition to serotonin and norepinephrine (NE) circuitries may result in enhanced antidepressant effects. Here, we investigated the pharmacological effects of a serotonin-preferring TRI-amitifadine (EB-1010, formerly DOV 21947). The effects of amitifadine (10 mg/kg ip.) on extracellular concentrations of monoamines and their metabolites in rat brain regions were investigated using the in vivo microdialysis technique. The effects of amitifadine on locomotor activity and stereotyped behavior were also evaluated. A major metabolite of amitifadine, the 2-lactam compound, was investigated for inhibition of monoamine uptake processes. Amitifadine markedly and persistently increased extracellular concentrations of serotonin, NE, and DA in prefrontal cortex. The extracellular concentrations of DA were also increased in the DA-rich areas striatum and nucleus accumbens. The extracellular concentrations of the metabolites of serotonin, 5-hydroxyindoleacetic acid, and DA, 3,4-dihydroxyphenylacetic and homovanillic acid, were also markedly decreased in brain regions. Amitifadine did not increase locomotor activity or stereotypical behaviors over a broad dose range. The lactam metabolite of amitifadine weakly inhibited monoamine uptake. Thus, amitifadine increased extracellular concentrations of serotonin, NE, and DA, consistent with TRI. Although amitifadine significantly increased DA in the nucleus accumbens, it did not induce locomotor hyperactivity or stereotypical behaviors. The enhancement of serotonin, NE, and DA in rat brain regions associated with depression suggest that amitifadine may have novel antidepressant activity.

Antipsychotic drugs: comparison in animal models of efficacy, neurotransmitter regulation, and neuroprotection.

Various lines of evidence indicate the presence of progressive pathophysiological processes occurring within the brains of patients with schizophrenia. By modulating chemical neurotransmission, antipsychotic drugs may influence a variety of functions regulating neuronal resilience and viability and have the potential for neuroprotection. This article reviews the current literature describing preclinical and clinical studies that evaluate the efficacy of antipsychotic drugs, their mechanism of action and the potential of first- and second-generation antipsychotic drugs to exert effects on cellular processes that may be neuroprotective in schizophrenia. The evidence to date suggests that although all antipsychotic drugs have the ability to reduce psychotic symptoms via D(2) receptor antagonism, some antipsychotics may differ in other pharmacological properties and their capacities to mitigate and possibly reverse cellular processes that may underlie the pathophysiology of schizophrenia.

Selective muscarinic receptor agonist xanomeline as a novel treatment approach for schizophrenia.

OBJECTIVE: There are significant unmet needs in the treatment of schizophrenia, especially for the treatment of cognitive impairment, negative syndrome, and cognitive function. Preclinical data suggest that agonists with selective affinity for acetylcholine muscarinic receptors provide a potentially new mechanism to treat schizophrenia. The authors studied xanomeline, a relatively selective muscarinic type 1 and type 4 (M(1) and M(4)) receptor agonist, to determine if this agent is effective in the treatment of schizophrenia. METHOD: In this pilot study, the authors examined the efficacy of xanomeline on clinical outcomes in subjects with schizophrenia (N=20) utilizing a double-blind, placebo-controlled, 4-week treatment design. Outcome measures included the Positive and Negative Syndrome Scale (PANSS) for schizophrenia, the Brief Psychiatric Rating Scale (BPRS), the Clinical Global Impression (CGI) scale, and a test battery designed to measure cognitive function in patients with schizophrenia. RESULTS: Subjects treated with xanomeline did significantly better than subjects in the placebo group on total BPRS scores and total PANSS scores. In the cognitive test battery, subjects in the xanomeline group showed improvements most robustly in measures of verbal learning and short-term memory function. CONCLUSIONS: These results support further investigation of xanomeline as a novel approach to treating schizophrenia.

Zonisamide prevents olanzapine-associated hyperphagia, weight gain, and elevated blood glucose in rats.

Olanzapine (OLZ), one of the second-generation atypical antipsychotics (SGAs), has shown relative advantages in patient adherence and outcomes. However, OLZ has also been associated with a higher incidence of weight gain than most other SGAs. Excessive weight gain may in turn contribute to long-term health concerns for some individuals. Zonisamide (ZNS), a medication approved in the United States as an adjunct in the management of epilepsy, has a diverse pharmacological profile, including sodium channel blockade, monoamine enhancement, and inhibition of carbonic anhydrase. ZNS has also been reported to cause weight loss in both humans and rodents. We hypothesized that this profile might be beneficial when co-administered with OLZ. To test this hypothesis, we evaluated the effects of OLZ on body weight, as well as the pathways known to regulate feeding behavior and arousal in the Sprague-Dawley rat. As indicated via c-Fos expression, we found an OLZ-induced activation in the nucleus accumbens and orexin neurons in the lateral hypothalamus. An OLZ-associated development of hyperphagia, weight gain and elevated blood glucose in the rat was also found. These outcomes were attenuated and reversed in the presence of concomitant ZNS. These results suggest the hypothesis that ZNS may effectively treat or prevent weight gain or metabolic changes associated with the SGAs. Future studies of this combination in patients through appropriately designed human clinical studies are encouraged.

Cholinergic dysfunction in a mouse model of Alzheimer disease is reversed by an anti-A beta antibody.

Disruption of cholinergic neurotransmission contributes to the memory impairment that characterizes Alzheimer disease (AD). Since the amyloid cascade hypothesis of AD pathogenesis postulates that amyloid beta (A beta) peptide accumulation in critical brain regions also contributes to memory impairment, we assessed cholinergic function in transgenic mice where the human A beta peptide is overexpressed. We first measured hippocampal acetylcholine (ACh) release in young, freely moving PDAPP mice, a well-characterized transgenic mouse model of AD, and found marked A beta-dependent alterations in both basal and evoked ACh release compared with WT controls. We also found that A beta could directly interact with the high-affinity choline transporter which may impair steady-state and on-demand ACh release. Treatment of PDAPP mice with the anti-A beta antibody m266 rapidly and completely restored hippocampal ACh release and high-affinity choline uptake while greatly reducing impaired habituation learning that is characteristic of these mice. Thus, soluble "cholinotoxic" species of the A beta peptide can directly impair cholinergic neurotransmission in PDAPP mice leading to memory impairment in the absence of overt neurodegeneration. Treatment with certain anti-A beta antibodies may therefore rapidly reverse this cholinergic dysfunction and relieve memory deficits associated with early AD.

Effect of the attention deficit/hyperactivity disorder drug atomoxetine on extracellular concentrations of norepinephrine and dopamine in several brain regions of the rat.

Atomoxetine is a selective inhibitor of norepinephrine transporters and is currently being used in the pharmacotherapy of attention deficit/hyperactivity disorder (ADHD). We have previously shown that atomoxetine increased extracellular (EX) concentrations of norepinephrine and dopamine in prefrontal cortex, but unlike the psychostimulant methylphenidate, did not alter dopamine(EX) in nucleus accumbens or striatum. Using the in vivo microdialysis technique in rat, we investigated the effects of atomoxetine on norepinephrine(EX) and dopamine(EX) concentrations in several other brain regions and also evaluated the role of inhibitory autoreceptors on atomoxetine-induced increases of norepinephrine(EX) concentrations. Atomoxetine (3mg/kg i.p.) increased norepinephrine(EX) robustly in prefrontal cortex, occipital cortex, lateral hypothalamus, dorsal hippocampus and cerebellum, suggesting that norepinephrine(EX) is increased throughout the brain by atomoxetine. In lateral hypothalamus and occipital cortex where dopamine(EX) was quantifiable, atomoxetine did not increase dopamine(EX) concentrations, in contrast to parallel increases of norepinephrine(EX) and dopamine(EX) in prefrontal cortex, indicating a unique effect in prefrontal cortex. Administration of the alpha(2)-adrenergic antagonist idazoxan 1h after atomoxetine resulted in increases in prefrontal cortical norepinephrine efflux greater than either compound alone, indicating an attenuating effect of the adrenergic autoreceptors on norepinephrine efflux.

Preclinical pharmacology of FMPD [6-fluoro-10-[3-(2-methoxyethyl)-4-methyl-piperazin-1-yl]-2-methyl-4H-3-thia-4,9-diaza-benzo[f]azulene]: a potential novel antipsychotic with lower histamine H1 receptor affinity than olanzapine.

FMPD [6-fluoro-10-[3-(2-methoxyethyl)-4-methyl-piperazin-1-yl]-2-methyl-4H-3-thia-4,9-diaza-benzo[f]azulene] is a potential novel antipsychotic with high affinity for dopamine D2 (Ki= 6.3 nM), 5-HT(2A) (Ki= 7.3 nM), and 5-HT6 (Ki= 8.0 nM) human recombinant receptors and lower affinity for histamine H1 (Ki= 30 nM) and 5-HT2C (Ki= 102 nM) human recombinant receptors than olanzapine. Oral administration of FMPD increased rat nucleus accumbens 3,4-dihyroxyphenylacetic acid concentrations (ED200 = 6 mg/kg), blocked 5-HT2A agonist-induced increases in rat serum corticosterone levels (ED50= 1.8 mg/kg), and inhibited the ex vivo binding of [125I]SB-258585 [4-iodo-N-[4-methoxy-3-(4-methyl-piperazin-1-yl)-phenyl]-benzenesulfonamide] to striatal 5-HT6 receptors (ED50= 10 mg/kg) but failed to inhibit ex vivo binding of [3H]pyrilamine to hypothalamic histamine H1 receptors at doses of up to 30 mg/kg. In electrophysiology studies, acute administration of FMPD selectively elevated the number of spontaneously active A10 (versus A9) dopamine neurons and chronic administration selectively decreased the number of spontaneously active A10 (versus A9) dopamine neurons. FMPD did not produce catalepsy at doses lower than 25 mg/kg p.o. In Fos-induction studies, FMPD had an atypical antipsychotic profile in the striatum and nucleus accumbens and increased Fos expression in orexin-containing neurons of the hypothalamus. FMPD produced only a transient elevation of prolactin levels. These data indicate that FMPD is an orally available potent antagonist of dopamine D2, 5-HT2A, and 5-HT6 receptors and a weak antagonist of H1 and 5-HT2C receptors. FMPD has the potential to have efficacy in treating schizophrenia and bipolar mania with a low risk of treatment-emergent extrapyramidal symptoms, prolactin elevation, and weight gain. Clinical trials are needed to test these hypotheses.

Case history: the discovery of fluoxetine hydrochloride (Prozac).

In the early 1970s, evidence of the role of serotonin (5-hydroxytryptamine or 5-HT) in depression began to emerge and the hypothesis that enhancing 5-HT neurotransmission would be a viable mechanism to mediate antidepressant response was put forward. On the basis of this hypothesis, efforts to develop agents that inhibit the uptake of 5-HT from the synaptic cleft were initiated. These studies led to the discovery and development of the selective serotonin-reuptake inhibitor fluoxetine hydrochloride (Prozac; Eli Lilly), which was approved for the treatment of depression by the US FDA in 1987. Here, we summarize this research and discuss the many challenges that we encountered during the development of fluoxetine hydrochloride, which has now been widely acknowledged as a breakthrough drug for depression.

The dual transporter inhibitor duloxetine: a review of its preclinical pharmacology, pharmacokinetic profile, and clinical results in depression.

Major depressive disorder (MDD) poses a significant health problem and is estimated to be the third most costly and disabling disorder in the United States. Pharmacotherapy of depression has been successful, but improvements in response rates, remission rates, side effects, compliance and faster onset of therapeutic action have become prime objectives in drug development. There is considerable support for the hypothesis that dysfunctional serotonergic or noradrenergic neurotransmission may be etiological in depressed patients. Duloxetine is a balanced and potent reuptake inhibitor of serotonin (5-HT) and norepinephrine (NE) being studied as an antidepressant medication. In this review, we highlight the preclinical pharmacology, pharmacokinetic profile, and effects of duloxetine in the pharmacotherapy of depression. Evidence for 5-HT and NE reuptake inhibition by duloxetine comes from in vitro and in vivo transporter binding and functional uptake studies. Taken together with efficacy data from in vivo microdialysis, electrophysiological and behavioral studies, it is evident that duloxetine is balanced as a dual serotonin norepinephrine uptake inhibitor in vivo. The clinical efficacy and safety of duloxetine in the treatment of MDD has been studied in 6 multicenter, randomized, double-blind, placebo-controlled trials. In these studies, duloxetine was found to be effective in the treatment of emotional/psychological and painful physical symptoms associated with depression. More importantly, duloxetine appears to have better response rates and remission from depressive symptoms, perhaps due to its ability to treat a wider range of symptoms.

Amantadine for weight gain associated with olanzapine treatment.

Patients with schizophrenia (Sch), schizoaffective, schizophreniform, or bipolar (BP) I disorders [Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV)]; not manic or acutely psychotic [Brief Psychiatric Rating Scale (BPRS) total score < or =45]; treated with olanzapine for 1-24 months; and who had gained > or =5% of their initial body weight were examined to determine whether amantadine could attenuate weight gain or promote weight loss. Olanzapine (Olz; 5-20 mg/day) was co-administered with double-blind treatment of 100-300 mg/day amantadine (Olz+Amt, n=60) or placebo (Olz+Plc, n=65). Visit-wise analysis of weight showed that weight change from baseline [last-observation-carried-forward (LOCF)] in the Olz+Amt group was significantly different from the Olz+Plc group at weeks 8 (P=0.042), 12 (P=0.029), and 16 (primary endpoint, mean+/-S.D.: -0.19+/-4.58 versus 1.28+/-4.26 kg, P=0.045). Mean BPRS total score, positive subscale, and anxiety-depression scores improved comparably in both groups, and Montgomery-Asberg Depression Rating Scale (MADRS) total score improved in the Olz+Amt group. Overall, amantadine was safe, was well tolerated, and attenuated weight gain or promoted weight loss in some patients who had gained weight during olanzapine therapy.

Treatment of glossodynia with olanzapine.

A 73-year-old white male with a 6-month history of glossodynia, unresponsive to clotrimazole troches, cevimeline, triamcinolone dental paste, paroxetine, and lorazepam presented to the dermatology clinic for consultation. Work-up revealed no oral abnormalities and no underlying systemic disorder. He denied symptoms consistent with a psychiatric disorder. A detailed free amnestic assessment by a board certified Geriatric Psychiatrist (John S. Kennedy, MD) found that the patient was oppressed by the pain. He did not meet the criteria for major depression nor did he have any anxiety disorder or delusions. Because of the presence of dysphoria and anticipatory anxiety secondary to glossodynia, the patient was started on olanzapine. Improvement of pain symptoms were noted within 3 days with full resolution of symptoms at 1- and 3-month follow-ups. Dysphoria and anticipatory anxiety remitted fully upon pain relief.

M4 muscarinic receptors regulate the dynamics of cholinergic and dopaminergic neurotransmission: relevance to the pathophysiology and treatment of related CNS pathologies.

Dopaminergic dysfunction is an important pathogenetic factor for brain pathologies such as Parkinson's disease, ADHD, schizophrenia, and addiction as well as for metabolic disorders and anorexia. Dopaminergic neurons projecting from the midbrain to forebrain regions, such as the nucleus accumbens and the prefrontal cortex, regulate motor and cognitive functions and coordinate the patterned response of the organism to sensory, affective, and rewarding stimuli. In this study, we showed that dopaminergic neurotransmission is highly dependent on M4 cholinergic muscarinic receptor function. Using in vivo microdialysis, we found elevated dopamine (DA) basal values and enhanced DA response to psychostimulants in the nucleus accumbens of M4 knockout mice. We also demonstrated impaired homeostatic control of cholinergic activity that leads to increased basal acetylcholine efflux in the midbrain of these animals. Thus, loss of M4 muscarinic receptor control of cholinergic function effectuates a state of dopaminergic hyperexcitability. This may be responsible for pathological conditions, in which appetitive motivation as well as affective and cognitive processing is impaired. We propose that M4 receptor agonists could represent an innovative strategy for the treatment of pathologies associated with hyperdopaminergia.

Clinical assessment of norepinephrine transporter blockade through biochemical and pharmacological profiles.

BACKGROUND: To assess the sensitivity of biochemical, physiological, and pharmacological markers of peripheral norepinephrine (NE) transporter (NET) function, we chronically antagonized NET by a range of doses of duloxetine [(+)-N-methyl-3-(1-naphthalenyloxy)-2 thiophenepropanamine], which blocks the NE reuptake process. METHODS AND RESULTS: Duloxetine was administered in a randomized, placebo-controlled study in 15 healthy volunteers. Plasma from duloxetine-treated subjects (ex vivo effect) dose-dependently decreased radioligand binding to human NET (maximum inhibition was 60%) (P=0.02). The dose of intravenous tyramine required to raise systolic blood pressure by 30 mm Hg (PD30) increased dose-dependently with duloxetine and was significant at the end of the 120-mg/d dosage (P<0.001). The plasma dihydoxyphenylglycol to NE (DHPG/NE) ratio was reduced significantly at 2 weeks of treatment with 80 mg/d duloxetine (11.3 at baseline, 3.4 at 240 mg/d, P<0.001). Plasma NE was significantly increased starting at 120 mg/d duloxetine. Urine results (corrected for 24-hour creatinine excretion) showed a dose-dependent change from the baseline urinary excretion for NE, DHPG, and the DHPG/NE ratio. The most sensitive measure, the DHPG/NE ratio, was significant at the 80-mg dose. Urinary NE excretion was significantly raised after 2 weeks of treatment with 80 mg/d duloxetine (P<0.001), the lowest dose used in the study. CONCLUSIONS: These findings suggest that the degree of NET blockade can be assessed with the plasma or urine DHPG/NE ratio and the pressor effect of tyramine. Also, the DHPG/NE ratio is more sensitive at the lower end of NET inhibition, whereas tyramine exhibits a linear relation, with NET inhibition commencing at a higher dose.