Antidepressant drugs affect dopamine uptake

Immunology of Physical Exercise: Is Equus caballus an Appropriate Animal Model for Human Athletes?

Domestic horses routinely participate in vigorous and various athletic activities. This enables the horse to serve as a model for studying athletic physiology and immunology in other species, including humans. For instance, as a model of physical efforts, such as endurance rides (long-distance running/aerobic exercise) and races (anaerobic exercise), the horse can be useful in evaluating post-exercise response. Currently, there has been significant interest in finding biomarkers, which characterize the advancement of training and adaptation to physical exercise in the horse. The parallels in cellular responses to physical exercises, such as changes in receptor expression and blood cell activity, improve our understanding of the mechanisms involved in the body's response to intense physical activity. This study focuses on the changes in levels of the pro- and anti-inflammatory cytokines and cellular response in the context of post-exercise immune response. Both the direction of changes in cytokine levels and cellular responses of the body, such as proliferation and expression of surface markers on lymphocytes, monocytes and neutrophils, show cross-functional similarities. This review reveals that horses are robust research models for studying the immune response to physical exercise in human athletes.

Radiological parameters to predict pancreatic texture: Current evidence and future perspectives

Preoperative prediction of the postoperative pancreatic fistula risk is critical in the current era of minimally invasive pancreatic surgeries to tailor perioperative management, thereby minimizing postoperative morbidity. Pancreatic duct diameter can be readily measured by any routine imaging used to diagnose pancreatic disease. However, radiological evaluation of pancreatic texture, an important determinant of pancreatic fistula, has not been widely used to predict the risk of postoperative pancreatic fistula. Qualitative and quantitative assessment of pancreatic fibrosis and fat fraction provides the basis for predicting pancreatic texture. Traditionally computed tomography has been utilized in identifying and characterizing pancreatic lesions and background parenchymal pathologies. With the increasing utilisation of endoscopic ultrasound and magnetic resonance imaging for evaluating pancreatic pathologies, elastography is emerging as a promising tool for predicting pancreatic texture. Also, recent studies have shown that early surgery for chronic pancreatitis is associated with better pain relief and preservation of pancreatic function. Pancreatic texture assessment can allow early diagnosis of chronic pancreatitis, facilitating early intervention. The present review outlines the current evidence in utilizing various imaging modalities for determining the pancreatic texture based on different parameters and image sequences. However, multidisciplinary investigations using strong radiologic-pathologic correlation are needed to standardize and establish the role of these non-invasive diagnostic tools in predicting pancreatic texture.

Developments of possible clinical diagnostic methods for parkinson's disease: event-related potentials

In this study, Event-Related Potential (ERP) analyzes were performed to detect cognitive impairments in PD with Deep Brain Stimulation (DBS). A total of 85 volunteers underwent ERP analysis and neuropsychological testing (NPT) to determine cognitive level. In ERP analyses, prolonged latencies were observed in PD groups. However, patients implanted with DBS showed a decrease in latencies, a decrease in symptoms and statistical improvements in both cognitive and attention skills. Considering all these data, ERP results are promising as a noninvasive method that can be used in both disease status and diagnosis of PD.

Characterization of Inflammatory Signals in BV-2 Microglia in Response to Wnt3a

Activation of microglia is one of the pathological bases of neuroinflammation, which involves various diseases of the central nervous system. Inhibiting the inflammatory activation of microglia is a therapeutic approach to neuroinflammation. In this study, we report that activation of the Wnt/β-catenin signaling pathway in a model of neuroinflammation in Lipopolysaccharide (LPS)/IFN-γ-stimulated BV-2 cells can result in inhibition of production of nitric oxide (NO), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α). Activation of the Wnt/β-catenin signaling pathway also results in inhibition of the phosphorylation of nuclear factor-κB (NF-κB) and extracellular signal-regulated kinase (ERK) in the LPS/IFN-γ-stimulated BV-2 cells. These findings indicate that activation of the Wnt/β-catenin signaling pathway can inhibit neuroinflammation through downregulating the pro-inflammatory cytokines including iNOS, TNF-α, and IL-6, and suppress NF-κB/ERK-related signaling pathways. In conclusion, this study indicates that the Wnt/β-catenin signaling activation may play an important role in neuroprotection in certain neuroinflammatory diseases.

Elucidating the Interaction between Pyridoxine 5'-Phosphate Oxidase and Dopa Decarboxylase: Activation of B6-Dependent Enzyme

Pyridoxal 5'-phosphate (PLP), the active form of vitamin B6, serves as a cofactor for scores of B6-dependent (PLP-dependent) enzymes involved in many cellular processes. One such B6 enzyme is dopa decarboxylase (DDC), which is required for the biosynthesis of key neurotransmitters, e.g., dopamine and serotonin. PLP-dependent enzymes are biosynthesized as apo-B6 enzymes and then converted to the catalytically active holo-B6 enzymes by Schiff base formation between the aldehyde of PLP and an active site lysine of the protein. In eukaryotes, PLP is made available to the B6 enzymes through the activity of the B6-salvage enzymes, pyridoxine 5'-phosphate oxidase (PNPO) and pyridoxal kinase (PLK). To minimize toxicity, the cell keeps the content of free PLP (unbound) very low through dephosphorylation and PLP feedback inhibition of PNPO and PLK. This has led to a proposed mechanism of complex formation between the B6-salvage enzymes and apo-B6 enzymes prior to the transfer of PLP, although such complexes are yet to be characterized at the atomic level, presumably due to their transient nature. A computational study, for the first time, was used to predict a likely PNPO and DDC complex, which suggested contact between the allosteric PLP tight-binding site on PNPO and the active site of DDC. Using isothermal calorimetry and/or surface plasmon resonance, we also show that PNPO binds both apoDDC and holoDDC with dissociation constants of 0.93 ± 0.07 μM and 2.59 ± 0.11 μM, respectively. Finally, in the presence of apoDDC, the tightly bound PLP on PNPO is transferred to apoDDC, resulting in the formation of about 35% holoDDC.

Hemodynamic management in brain dead donors

Donor management is the key in the complex donation process, since up to 20% of organs of brain death donors (DBD) are lost due to hemodynamic instability. This challenge is made more difficult due to the lack of strong recommendations on therapies for hemodynamic management in DBDs and more importantly to the epidemiologic changes in these donors who are becoming older and with more comorbidities (marginal donors). In the present manuscript we aimed at summarizing the available evidence on therapeutic strategies for hemodynamic management (focusing on vasoactive drugs) and monitoring (therapeutic goals). Evidence on management in elderly DBDs is also summarized. Donor management continues critical care but with different and specific therapeutic goals since the number of donor goals met is related to the number of organs retrieved and transplanted. Careful monitoring of selected parameters (possibly including serial echocardiography) is the clinical tool able to guarantee the achievement and maintaining of therapeutic goals. Despide worldwide differences, norepinephrine is the vasoactive of choice in most countries but, whenever higher doses (> 0.2 mcg/kg/min) are needed, a second vasoactive drug (vasopressin) is advisable. Hormonal therapy (desmopressin, corticosteroid and thyroid hormone) are suggested in all DBDs independently of hemodynamic instability. In the single patient, therapeutic regimen (imprimis vasoactive drugs) should be chosen also according to the potential organs retrievable (i.e. heart vs liver and kidneys).

Peripheral vascular disease: preclinical models and emerging therapeutic targeting of the vascular endothelial growth factor ligand-receptor system

Introduction: Vascular endothelial growth factor (VEGF)-A is a sought therapeutic target for PAD treatment because of its potent role in angiogenesis. However, no therapeutic benefit was achieved in VEGF-A clinical trials, suggesting that our understanding of VEGF-A biology and ischemic angiogenic processes needs development. Alternate splicing in VEGF-A produces pro- and anti-angiogenic VEGF-A isoforms; the only difference being a 6-amino acid switch in the C-terminus of the final 8th exon of the gene. This finding has changed our understanding of VEGF-A biology and may explain the lack of benefit in VEGF-A clinical trials. It presents new therapeutic opportunities for peripheral arterial disease (PAD) treatment.Areas covered: Literature search was conducted to include: 1) predicted mechanism by which the anti-angiogenic VEGF-A isoform would inhibit angiogenesis, 2) unexpected mechanism of action, and 3) how this mechanism revealed novel signaling pathways that may enhance future therapeutics in PAD.Expert opinion: Inhibiting a specific anti-angiogenic VEGF-A isoform in ischemic muscle promotes perfusion recovery in preclinical PAD. Additional efforts focused on the production of these isoforms, and the pathways altered by modulating different VEGF receptor-ligand interactions, and how this new data may allow bedside progress offers new approaches to PAD are discussed.I.

Anticancer Activity of Ganoderic Acid DM: Current Status and Future Perspective

Ganoderma lucidum is a mushroom that has a long history of medicinal use in the Far East countries as this mushroom is revered for its supposed miracle cures and life improving properties. Recently, this mushroom has come under scientific scrutiny to examine the possibility of finding biologically active compounds that may have an impact on human physiology. The main category of biologically active compounds produced in the G. lucidum, are the triterpenoids, which are known as Ganoderic Acids. In this review, we discuss one Ganoderic Acid in particular known as Ganoderic Acid-DM (GA-DM) that is extracted from the Ganoderma lucidum mushroom. We will discuss GA-DM as a potential therapeutic candidate for treating a number of diseases yet will focus on the potential to be used as an alternative or supplemental therapeutic agent in regards to various cancer types. The urge for this promising therapeutic agent is that GA-DM is capable of inducing cell death in cancer cells while exhibiting minimal toxicity to normal bystander cells. Furthermore, this review will look at GA-DM's ability to stimulate an immune response in the tumor environment to potentially provide long-term protection from the malignant tumors. We will also discuss the known routes of administration of GA-DM and pose the advantages and disadvantages of each route in a comparative manner. Finally, we will cover current status of the roles GA-DM may have as a therapeutic agent in respect to different cancer types as wells as discuss about its future perspective as a therapeutic candidate in other diseases as well.

Tenofovir rescue therapy for chronic hepatitis B patients after multiple treatment failures

AIM: To evaluate the efficacy and safety of tenofovir disoproxil fumarate (TDF) for chronic hepatitis B (CHB) patients after multiple failures.

METHODS: A total of 29 CHB patients who had a suboptimal response or developed resistance to two or more previous nucleoside/nucleotide analogue (NA) treatments were included. Study subjects were treated with TDF alone (n = 13) or in combination with lamivudine (LAM, n = 12) or entecavir (ETV, n = 4) for ≥ 6 mo. Complete virologic response (CVR) was defined as an achievement of serum hepatitis B virus (HBV) DNA level ≤ 60 IU/mL by real-time polymerase chain reaction method during treatment. Safety assessment was based on serum creatinine and phosphorus level. Eleven patients had histories of LAM and adefovir dipivoxil (ADV) treatment and 18 patients were exposed to LAM, ADV, and ETV. Twenty-seven patients (93.1%) were hepatitis B e antigen (HBeAg) positive and the mean value of the baseline serum HBV DNA level was 5.5 log IU/mL ± 1.7 log IU/mL. The median treatment duration was 16 mo (range 7 to 29 mo).

RESULTS: All the patients had been treated with LAM and developed genotypic and phenotypic resistance to it. Resistance to ADV was present in 7 patients and 10 subjects had a resistance to ETV. One patient had a resistance to both ADV and ETV. The cumulative probabilities of CVR at 12 and 24 mo of TDF containing treatment regimen calculated by the Kaplan Meier method were 86.2% and 96.6%, respectively. Although one patient failed to achieve CVR, serum HBV DNA level decreased by 3.9 log IU/mL from the baseline and the last serum HBV DNA level during treatment was 85 IU/mL, achieving near CVR. No patients in this study showed viral breakthrough or primary non-response during the follow-up period. The cumulative probability of HBeAg clearance in the 27 HBeAg positive patients was 7.4%, 12%, and 27% at 6, 12, and 18 mo of treatment, respectively. Treatment efficacy of TDF containing regimen was not statistically different according to the presence of specific HBV mutations. History of prior exposure to specific antiviral agents did not make a difference to treatment outcome. Treatment efficacy of TDF was not affected by combination therapy with LAM or ETV. No patient developed renal toxicity and no cases of hypophosphatemia associated with TDF therapy were observed. There were no other adverse events related to TDF therapy observed in the study subjects.

CONCLUSION: TDF can be an effective and safe rescue therapy in CHB patients after multiple NA therapy failures.

Tricyclics and malignant syndrome

A clinical and biological pattern similar to that of neuroleptic malignant syndrome is reported in a depressed patient treated with trimipramine, without any concomitant use of neuroleptics. The antidopaminergic properties of this drug, one of the tricyclic antidepressants, may account for this uncommon side effect.

Dopamine, schizophrenia, mania, and depression: Toward a unified hypothesis of cortico-striatopallido-thalamic function

Considerable evidence from preclinical and clinical investigations implicates disturbances of brain dopamine (DA) function in the pathophysiology of several psychiatric and neurologic disorders. We describe a neural model that may help organize theseindependent experimental observations. Cortical regions classically associated with the limbic system interact with infracortical structures, including the nucleus accumbens, ventral pallidum, and dorsomedial nucleus of the thalamus. In our model, overactivity in forebrain DA systems results in the loss of lateral inhibitory interactions in the nucleus accumbens, causing disinhibition of pallidothalamic efferents; this in turn causes rapid changes and a loss of focused corticothalamic activity in cortical regions controlling cognitive and emotional processes. These effects might be manifested clinically by some symptoms of psychoses. Underactivity of forebrain DA results in excess lateral inhibition in the nucleus accumbens, causing tonic inhibition of pallidothalamic efferents; this perpetuates tonic corticothalamic activity and prevents the initiation of new activity in other critical cortical regions. These effects might be manifested clinically by some symptoms of depression. This model parallels existing explanations for the etiology of several movement disorders, and may lead to testable inferences regarding the neural substrates of specific psychopathologies.

The effects of psychotherapy on neural responses to rewards in major depression

BACKGROUND

Unipolar major depressive disorder (MDD) is characterized by anomalous neurobiological responses to pleasant stimuli, a pattern that may be linked to symptoms of anhedonia. However, the potential for psychotherapy to normalize neurobiological responses to pleasant stimuli has not been evaluated.

METHODS

Twelve adults with and 15 adults without MDD participated in two identical functional magnetic resonance imaging scans that used a Wheel of Fortune task. Between scans, MDD outpatients received Behavioral Activation Therapy for Depression, a psychotherapy modality designed to increase engagement with rewarding stimuli and reduce avoidance behaviors.

RESULTS

Seventy-five percent of adults with MDD were treatment responders, achieving post-treatment Hamilton Rating Scale for Depression score of six or below. Relative to changes in brain function in the matched nondepressed group, psychotherapy resulted in functional changes in structures that mediate responses to rewards, including the paracingulate gyrus during reward selection, the right caudate nucleus (i.e., the dorsal striatum), during reward anticipation, and the paracingulate and orbital frontal gyri during reward feedback. There was no effect of diagnostic status or psychotherapy on in-scanner task-related behavioral responses.

CONCLUSIONS

Behavioral Activation Therapy for Depression, a psychotherapy modality designed to increase engagement with rewarding stimuli and reduce avoidance behaviors, results in improved functioning of unique reward structures during different temporal phases of responses to pleasurable stimuli, including the dorsal striatum during reward anticipation.

A registry-based, case-control investigation of Parkinson's disease with and without cognitive impairment

In approximately 40% of the patients, Parkinson's disease (PD) is complicated by cognitive impairment. The objective of this study was to evaluate the impact of cognitive impairment on disease severity and motor function in idiopathic PD patients. Forty-one PD patients with cognitive impairment (PD-CI) (Mini-Mental State Examination < or =24) and 41 PD patients without cognitive impairment (PD-Control) matched for age at onset and duration of the disease were examined using the Unified Parkinson's Disease Rating Scale (UPDRS). PD patients with cognitive impairment had overall poorer motor function, worse rigidity (both axial and limb) and bradykinesia, as well as worse performance in activities of daily living compared with matched PD patients without cognitive impairment. This could either be attributed to a direct effect of cognitive impairment on parkinsonian symptoms or to decreased compliance of patients during clinical examination. PD patients should be routinely and carefully screened for dementia and caregivers should be aware of the effect of dementia on PD.

Dopaminergic abnormalities in amygdaloid nuclei in major depression: a postmortem study

BACKGROUND

A deficiency of mesolimbic dopamine (DA) is a leading candidate for the etiology of certain symptoms of depression (e.g., anhedonia and loss of motivation). Here we show amounts of dopaminergic proteins in the amygdala, a key brain structure involved in the integration of emotions and stress, in subjects with major depression and in psychiatrically normal control subjects.

METHODS

The specific binding of [(125)I]RTI 55 to the DA transporter, [(3)H]SCH 23390 to the D1 receptor and [(125)I]epidepride to D2/D3 receptors were measured in the right amygdaloid complex in postmortem brains from 11 subjects with major depression and 11 matched control subjects.

RESULTS

The binding of [(125)I]RTI 55 to DA transporter was significantly lower in the basal and central amygdaloid nuclei, whereas the binding of [(125)I]epidepride to D2/D3 receptors was significantly higher in the basal, central, and lateral amygdaloid nuclei in major depression compared with control subjects. No difference in the binding of [(3)H]SCH 23390 to D1 receptors was observed.

CONCLUSIONS

Given that DA depletion in rats can induce a reduction in the DA transporter and an upregulation of D2/D3 receptors, our data are consistent with the hypothesis that major depression is associated with a deficiency of mesolimbic DA.

Permanent dopaminergic alterations in the n. accumbens after prenatal stress

It has been suggested that stress during the initial stages of human life may serve as a predisposing factor to mental illness. Recently, we reported that in pregnant rats, stress induces an increase of behavioral depression in the female offsprings when adult. This article describes the effect of prenatal stress on central dopaminergic transmission during adulthood. The offspring of stressed mothers showed an increase of behavioral depression in the Porsolt test and a reduction of DOPAC, HVA, and DOPAC/DA index in the n. accumbens. The effect on the right accumbens was more marked than on the left. A great body of information exists to suggest that depression is related to a decrease of dopaminergic neurotransmission, and the present data provide new evidence in support of the hypothesis that maternal stress during gestation increases the risk of depression in the offspring. We are also reporting a hitherto uncommented relationship between behavioral depression in the Porsolt test and the decrease of dopamine transmission in the n. accumbens.

Dopamine and melatonin in the nucleus accumbens may be implicated in the mode of action of antidepressant drugs

The effect of chronic systemic treatment (once a day for 2-3 weeks) with different antidepressant drugs (desipramine, mianserin, fluvoxamine 15 mg/kg per day i.p. or s.c.) on the behavioral responses elicited by intra-accumbens injection of graded doses (1-10,000 ng) of apomorphine and two doses (10 and 100 ng) of melatonin was investigated in rats. Treatment with antidepressant drugs consistently facilitated apomorphine-induced hypermotility, but differentially influenced apomorphine-induced hypomotility. The drugs completely antagonized melatonin-induced behavioral changes (hypomotility and increased duration of sniffing). The data suggest that chronic treatment with antidepressant drugs results in postsynaptic dopamine receptor supersensitivity in the nucleus accumbens, a terminal area of the mesolimbic dopaminergic system. It is postulated that the development of supersensitivity may be mediated by the inhibition of melatonin-induced effects observed after acute and chronic treatment with these antidepressants. The present findings may be relevant for the mode of therapeutic action of antidepressant drugs.

Neural symptoms induced by tricyclic antidepressants: phenomenology and pathophysiology

The authors review the literature describing the neural symptoms induced by tricyclic antidepressants, especially tremor, seizures, akathisia, myoclonus, dyskinesia and delirium. Sedation, modifications of sleep, memory and appetite are also described. Tremor and myoclonus are the most frequent drug-induced neural symptoms. Delirium is most often caused by high-dosage treatments. The pathophysiology of akathisia and dyskinesia raises important questions concerning the mode of action of antidepressants.

Antidepressant drugs increase the locomotor hyperactivity induced by MK-801 in rats

MK-801, a non-competitive NMDA receptor antagonist, induced the locomotor hyperactivity in rats. Imipramine (IMI), amitriptyline (AMI), citalopram (CIT) given acutely increased the MK-801-induced locomotor hyperactivity. Mianserin (MIA) showed a similar but weaker effect. Haloperidol completely blocked the hyperactivity induced by the antidepressant drug (AD) + MK-801. Prazosin had an only weak antagonistic effect. Repeated treatment with AD increased the MK-801 locomotor hyperactivity to a greater extent than acute treatment. This effect was completely blocked by haloperidol and only partly by prazosin. The obtained results indicate that the dopamine system may be involved, at least in part, in the potentiating effect of the combined treatment with AD + MK-801.

Paraganglionic cell response to chronic imipramine and handling stress: an ultrastructural study

The ultrastructure and connectivity of monoamine-storing paraganglionic cells in the rat superior cervical ganglion were investigated following chronic treatment with imipramine (Tofranil, Ciba-Geigy) and compared with uninjected unhandled controls and saline injected animals. The study reveals a significant decrease in the number of dense core vesicles in the drug-treated group (P less than 0.001) which is regarded as a specific effect due to receptor blocking actions of imipramine. A significant reduction in the maximum diameter of the external rim and internal cores of the vesicles (P less than 0.05) in the drug-treated group is mimicked to a certain extent by saline injections, indicating a mixed effect of stress handling and specific alteration. Although the paraganglionic cell morphology is unaltered in the group comparisons, the interrelationship of the paraganglionic cells to surrounding neural processes is significantly altered in both the control versus saline and the control versus drug group comparisons (P less than 0.05). The drug- and saline-induced alterations of neural connectivity may reflect stress-induced general changes demonstrating the plasticity of the paraganglionic cell population.

Possible role of dopamine D1 receptor in the behavioural supersensitivity to dopamine agonists induced by chronic treatment with antidepressants

The effect of chronic treatment with antidepressants (ADs) on the behavioral responses to LY 171555, a selective D2 receptor agonist, SKF 38393, a selective D1 receptor agonist, and B-HT 920, a selective DA autoreceptor agonist, was studied in rats. In normal rats small, intermediate and high doses of LY 171555 produced hypomotility, hyperactivity and stereotypies, respectively. Chronic but not acute pretreatment with imipramine (IMI) greatly potentiated the motor stimulant effect of LY 171555, but failed to modify its stereotypic and sedative effect. The potentiation of the motor stimulant effect of LY 171555 was observed also after chronic, but not acute, treatment with desmethylimipramine (DMI), mianserin (MIA) or repeated electroconvulsive shock (ECS). Chronic treatment with IMI failed to modify the effect of SKF 38393 (motor stimulation, grooming and penile erection), but reversed the sedative effect of B-HT 920 into a motor stimulant response. The motor stimulant response to LY 171555 in IMI-pretreated animals was suppressed by L-sulpiride, a D2 antagonist, and by a combination of reserpine with alpha-methyltyrosine (alpha-MT), but it was only partially antagonized by high doses of SCH 23390, a selective D1 antagonist. The results indicate that chronic treatment with ADs potentiates the behavioural responses mediated by the stimulation of postsynaptic D2 receptors in the mesolimbic system and suggest that this behavioural supersensitivity is due to enhanced neurotransmission at the D1 receptor level.

Effects of haloperidol on recall and information processing in verbal and spatial learning

1. Normal male subjects were tested with either a multi-trial word list learning test or a spatial analogue prior to administration of either 4 mg. or 10 mg. of oral haloperidol. Six hours after drug administration subjects who had previously received the verbal test were administered the spatial test, and vice versa, so for each test there was a no-drug control group, a group tested after receiving 4 mg. of haloperidol, and a group tested after a 10 mg. dose. 2. Both the verbal and spatial learning tests yield multidimensional measures of components of memory and learning, including measures sensitive to effort-demanding and more automatic information processing operations. 3. Results showed no differences for either test among the pre-drug control group and the 4 mg. and 10 mg. groups, with only one minor exception. 4. The lack of significant results cannot be attributed to insensitivity of the test instruments used, since previous studies have documented sensitivity to a number of clinical conditions and to aging. 5. Results have implications regarding clinical effects of haloperidol. A theory that links dopaminergic functioning with effortful information processing underlying memory and learning was not supported.

In vivo neurochemical profile of dopamine uptake inhibitors and releasers in rat caudate-putamen

The in vivo neurochemical profile of recently synthesized dopamine (DA) uptake inhibitors (Lu 19-005, Lu 17-133 and GBR 12.921) is described. The antidepressant, nomifensine, as well as another typical DA uptake inhibitor, methylphenidate, was also tested with the microdialysis technique. Most of the new DA uptake inhibitors induced a gradual dose- and time-dependent accumulation of extracellular DA with a weak influence on DA metabolites, similar to that of methylphenidate. Nomifensine, however, caused a DA overflow during the first hour after injection. This was distinguishable from the effect of other uptake inhibitors but comparable to amphetamine. The moderate increase of DOPAC induced by nomifensine compared to the marked decrease produced by amphetamine corroborates reports that the DA 'release' induced by these drugs is mediated by different mechanisms, originating from different intracellular storage pools of DA. The fact that nomifensine can be distinguished from other uptake inhibitors shows clearly that evaluation of dynamic changes in transmitter overflow provides information pertinent to the overall neurochemical characterization of a drug.

The continuous performance test, identical pairs version: II. Contrasting attentional profiles in schizophrenic and depressed patients

The Continuous Performance Test-Identical Pairs version was administered to 14 schizophrenic patients, 17 depressed patients, and 28 normal controls. The task was divided into verbal and spatial stimuli, as well as no-distraction and distraction (verbal and auditory) conditions. Both patient groups displayed attentional impairments compared to normal subjects, but they differed from each other in specific profiles. Schizophrenic patients were characterized by a global impairment and a particular inability to focus on the critical stimuli, whether verbal or spatial. They also made an excess of random responses throughout the task but showed no evidence that attention declined from its initial level over time. Depressed patients did not display a global attentional deficit but did show a specific inability to attend to spatial as compared to verbal stimuli and, in particular, a confusion when the spatial stimuli were only slightly different. Performance on a secondary task in response to a change in expectation improved dramatically for depressed but not schizophrenic patients, suggesting a more efficient allocation strategy, a greater reserve of processing capacity, or more dependence on motivational factors in depressed patients. Schizophrenic and depressed patients were alike in extent of distractibility. Whereas normal controls improved with the onset of external distraction, schizophrenic and depressed patients deteriorated to an equal extent. Distractibility was thus concluded to be a correlate of acute psychiatric illness and not specific for schizophrenia.

Dopamine uptake by platelets is selective, temperature dependent and not influenced by the dopamine-D1 or dopamine-D2 receptor

The human platelet, which takes up and releases dopamine, has been proposed as a peripheral model for the study of dopaminergic neurons in the central nervous system (CNS). In addition, the platelet has been shown to possess membrane components with pharmacological properties similar to the dopamine-D1 (DA-D1) and D2 (DA-D2) receptor on dopaminergic neurons. We have therefore studied the specificity of the platelet uptake system for dopamine and, as dopamine uptake comprises both internalised and membrane bound dopamine, the contribution of the DA-D1 and DA-D2 receptor to the uptake of dopamine has been assessed. Significant uptake of 3H-dopamine by platelet rich plasma (PRP) occurred after 10 min incubation at 37 degrees C, uptake being maximal after 90 min. In contrast, at 4 degrees C no uptake of 3H-dopamine occurred up to 60 mins incubation but at 20 degrees C was approximately 8% of the 60 min uptake at 37 degrees C. The neurotransmitters serotonin and dopamine inhibited dopamine uptake by platelets in a dose dependent manner. Uptake of dopamine appeared to be via two systems, one of high affinity with low capacity and the other of lower affinity but high capacity. In contrast, noradrenaline, adrenaline, acetylcholine, gamma-aminobutyric acid and histamine (10 microM) had no effect on dopamine uptake by platelets. The DA-D1 receptor antagonist SCH 23390 (10 microns) and the DA-D2 receptor antagonists (10 microM) spiperone, domperidone and (+)-butaclamol did not significantly affect dopamine uptake by platelets. In addition, ouabain and desipramine (100 microM) inhibited dopamine uptake by 21% and 24% respectively whilst reserpine and imipramine (100 microM) increased uptake by 14% and 15%. We therefore conclude that platelets take up dopamine via a selective, temperature dependent mechanism. Our data also suggest that dopamine uptake by platelets does not involve the DA-D1 or DA-D2 receptor.

Importance of D-2 mechanisms in the reversal of reserpine hypothermia in the mouse

The D-2 agonist LY 171555 (0.05, 0.1, 0.2 mg kg-1 s.c.) but not the D-1 agonist SK&F 38393 (5, 10, 20 mg kg-1 s.c.) reduced reserpine-induced hypothermia (RIH) in mice. This effect was antagonized by the D-2 antagonist (-)-sulpiride (50 mg kg-1 i.p.) but not by the D-1 antagonist SCH 23390 (0.1 mg kg-1 s.c.). SK&F 38393 (20 and 1 mg kg-1 s.c.) did not alter the effect of LY 171555 (0.1 and 0.2 mg kg-1) on RIH, but administration of both LY 171555 (0.2 mg kg-1 s.c.) and SK&F 38393 (1 mg kg-1 s.c.) antagonized the reserpine-induced sedation.

The pharmacological profile of Org 6906, a potential non-sedative antidepressant that combines monoamine uptake inhibition with alpha 2-adrenolytic activity

(dl)-(5 alpha,8 alpha,9 alpha)-5,8,9,10-Tetrahydro-5,9- methanobenzocycloocten-8-amine hydrochloride (Org 6906) is a potential new antidepressant agent, with a neurochemical profile quite different from that of the classical tricyclic antidepressant drugs. The compound was found active in behavioural tests which are considered to be predictive for antidepressant activity, such as the muricidal test in the rat and the acquired immobility model. Neurochemical studies showed that Org 6906 was an inhibitor of the reuptake of monoamines both in vitro and ex-vivo without having appreciable anticholinergic, antihistaminergic or alpha 1-adrenolytic activity. The facilitatory effect on monoaminergic neurotransmission was confirmed by the reversal of hypothermia induced by reserpine. The drug Org 6906 appeared to have selective alpha 2-adrenolytic properties. It facilitated potassium-stimulated release of noradrenaline from slices of cortex, displaced [3H]rauwolscine and [3H]dihydroergocryptine from their binding sites but only weakly blocked alpha 1-adrenoceptors. The alpha 2-adrenolytic properties were also apparent in behavioural interaction models. The compound antagonized the sleep-inducing effects of clonidine in chicks and mice and it antagonized the mydriasis induced by clonidine in the rat. Finally, it was shown that the two enantiomers of Org 6906 contributed almost equally to the relevant neurochemical and behavioural properties.

Chronic treatment with antidepressants decreases the number of [3H]SCH 23390 binding sites in the rat striatum and limbic system

Binding of [3H]SCH 23390 to dopamine D-1 receptors and of [3H]spiperone to D-2 sites was measured in identical membrane preparations of the striatum and limbic system of rats treated chronically (twice daily, for two weeks) with antidepressants. Chronic administration of imipramine, amitriptyline, mianserin, citalopram, bupropion, iprindole and electroconvulsive shocks, but not benztropine or cyproheptadine (non-antidepressants) decreased the number of [3H]SCH 23390 binding sites, while no change in the parameters of [3H]spiperone binding was observed. The serotonin2 receptor antagonist ketanserin when added to the incubation medium had no effect on [3H]SCH 23390 binding to D-1 sites. The results suggest that D-1 receptor subsensitivity is a component of the therapeutic effect of antidepressants.