Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0036341 (schizophrenia)
 60,220 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Adenosine diphosphate (ADP) stimulates the synthesis of prostaglandin E1 (PGE1) in lysed platelets from normal subjects, patients with affective illness but not in platelets from cases of schizophrenia. The stimulation is concentration-dependent and follows a curve which is mildly sigmoid in the normal, markedly sigmoid in depression and hyperbolic in mania.
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PMID:Effect of ADP on PGE1 formation in blood platelets from patients with depression, mania and schizophrenia. 120 54

The function of the neuromodulator, adenosine, has been thoroughly examined during the last two decades. Adenosine inhibits the release of several neurotransmitters and endogenous adenosine is supposed to have sedative and anticonvulsive properties. Lately, it has been discussed whether neuropsychiatric disorders could be treated with adenosynergic drugs. In patients with anxiety disorder a first clinical trial with the reuptake inhibitor dipyridamole was not successful. Disorders of the basal ganglia and schizophrenia might be positively influenced by newly developed A2-receptor ligands. A1-receptor agonists might prove to be neuroprotective; they also could be of importance in the treatment of epilepsy. Selective A1-receptor antagonists might be used in the treatment of depressive disorders and of neurodegenerative disorders such as Alzheimer's disease. The adenosine receptor antagonist, caffeine, is widely used in the treatment of migraine; more selective antagonists would provide a more powerful treatment.
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PMID:[Perspectives on the therapy of neuropsychiatric diseases with adenosinergic substances]. 775 49

The ventral striatum is included in brain circuits which connect brain areas classically ascribed to the motor or to the limbic system. In fact, the ventral striatum is involved in the connection between motivationally relevant stimuli and adaptive behaviours. Dopamine neurotransmission in the ventral striatum is essential for the increase in motor activity produced by motivational, salient, stimuli, such as food or novelty or by the administration of psychostimulants. Adenosine plays a role opposite to dopamine in the striatum and adenosine agonists produce similar behavioural effects as dopamine antagonists. On the other hand, adenosine antagonists, like caffeine, produce similar effects to increased dopaminergic neurotransmission in the striatum. Specific antagonistic interactions between specific subtypes of adenosine and dopapaine receptors in the basal ganglia play an essential role in the behavioural effects of adenosine agonists and antagonists. In particular, a strong antagonistic interaction between adenosine A2A and dopamine D2 receptors seems to take place in the striopallidal GABAergic neurons which originate in the ventral striatum. Therefore, adenosine A(ZA) agonists provide a potential new treatment for schizophrenia, since the dopamine D2 receptors of the ventral striopallidal neurons appear to be involved in the antipsychotic effects of neuroleptics. In fact, in animal models, the adenosine A2A agonist CGS 21680 has a profile of antipsychotic with a low liability to induce extrapyramidal side effects.
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PMID:Adenosine-dopamine interactions in the ventral striatum. Implications for the treatment of schizophrenia. 934 76

It is well known that the nucleoside adenosine exerts a modulatory influence in the central nervous system by activating G protein coupled receptors. Adenosine A2A receptors, the subject of the present review, are predominantly expressed in striatum, the major area of the basal ganglia. Activation of A2A receptors interferes with effects mediated by most of the principal neurotransmitters in striatum. In particular, the inhibitory interactions between adenosine acting on A2A receptors and dopamine acting on D2 receptors have been well examined and there is much evidence that A2A receptors may be a possible target for future development of drugs for treatment of Parkinson's disease, schizophrenia and affective disorders. Our understanding of the role of striatal A2A receptors has increased dramatically over the last few years. New selective antibodies, antagonist radioligands and optimized in situ hybridization protocols have provided detailed information on the distribution of A2A receptors in rodent as well as primate striatum. Studies on the involvement of A2A receptors in the regulation of DARPP-32 and the expression of immediate early genes, such as nerve growth factor-induced clone A and c-fos, have pointed out an important role for these receptors in regulating striatopallidal neurotransmission. Moreover, by using novel selective antagonists for A2A receptors and transgenic mice lacking functional A2A receptors, crucial information on the behavioral role of striatal A2A receptors has been provided, especially concerning their involvement in the stimulatory action of caffeine and the anti-Parkinsonian properties of A2A receptor antagonists. In the present review, current knowledge on the distribution, biochemistry and function of striatal A2A receptors is summarized.
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PMID:Distribution, biochemistry and function of striatal adenosine A2A receptors. 1050 34

Adenosine A2A receptors (A2AR) and dopamine D2 receptors (D2R) are highly concentrated in the striatum, where they are co-localized and exert reciprocal antagonistic interactions. It has been suggested that the A2R/D2R interactions might provide a therapeutic approach for basal ganglia disorders, such as Parkinson's disease, and schizophrenia. In the present work evidence is presented for the existence of an A2AR/D2R interaction in human brain by using quantitative autoradi- ography. The areas analyzed were the dorsal caudate nucleus and putamen. Parallel studies were performed in rat striatal sections. The A2AR agonist CGS 21680 was found to significantly increase IC50 values of competitive inhibition curves of the D2R/D3R antagonist [125I]iodosulpiride vs dopamine both in rat striatal and human striatal brain sections.
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PMID:Adenosine A2A agonist CGS 21680 decreases the affinity of dopamine D2 receptors for dopamine in human striatum. 1143 7

Adenosine has been proposed to contribute to the pathophysiology of schizoprenia and as a target for therapeutic intervention. In the lack of direct adenosine agonists, allopurinol may indirectly elevate adenosine levels by inhibiting degradation of purines. We report two cases of poorly responsive schizophrenic patients who improved considerably with add-on allopurinol 300 mg/day. Their clear clinical improvement warrant further investigation of allopurinol, as well as other purinergic strategies, for the treatment of schizophrenia.
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PMID:Allopurinol augmentation for poorly responsive schizophrenia. 1145 38

In the p50 suppression paradigm, when two auditory stimuli are presented 500 ms apart, the amplitude of the second response (S2), compared with the first (S1), is markedly attenuated in healthy subjects. This is an index of sensory gating. Most schizophrenic patients fail to inhibit the p50 response to the second stimulus, which is assumed to reflect an inhibitory deficit. Adenosine is a neuromodulator with mostly inhibitory activity which is released by physiological stimuli. Since this inhibitory pattern resembles the phenomenon of sensory gating, the contribution of adenosine to p50 suppression was investigated in normal volunteers after treatment with the adenosine antagonist theophylline or placebo. P50 recordings were conducted in thirteen healthy subjects at baseline and 5, 30, 60, and 90 min after oral administration of theophylline (0.66 mg/kg, maximum dose of 500 mg) or placebo in a cross-over design. Baseline results from 17 drug-treated schizophrenic patients were included for comparison. Compared with placebo, theophylline treatment significantly increased P50 ratio (S2/S1) from 0.28 +/- 0.03 to 0.82 +/- 0.11 at 30 min and 0.61 +/- 0.07 at 60 min (mean +/- SEM), which were not significantly different from the schizophrenia group (0.74 +/- 0.05). The increased p50 ratio by theophylline was due to a combined decrease in S1 and increase in S2 amplitude. The impairment of p50 suppression by theophylline in normal subjects suggests a modulatory role of adenosine in sensory gating, which may be related to p50 suppression deficit in schizophrenia and is in agreement with a hypoadenosinergic model of schizophrenia.
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PMID:The adenosine antagonist theophylline impairs p50 auditory sensory gating in normal subjects. 1237 99

Adenosine A (2A) receptors have been implicated in the pathophysiology of schizophrenia by clinical, anatomical, biochemical and genetic studies. We hypothesized that a genetically determined low number of adenosine A (2A) receptors could be a vulnerability factor for the development of the disease. The density of adenosine A (2A) receptors was investigated in human postmortem striatum of patients with schizophrenia (n = 9) and matched controls ( n= 9) using [ H)CGS 21680 as a radioligand probe. The maximum number of binding sites (B) (max) was 70% higher in patients with schizophrenia than in matched controls (609.4 +/- 259.1 354.0 +/- 156.4 fmol/mg protein, p=0.04). No significant difference could be discerned for the affinity of caffeine for adenosine A receptors between patients and controls. The increase in receptor density correlated with the dose of antipsychotic medication in chlorpromazine equivalents (r =0.61, = 0.014). We failed to provide evidence for a genetically determined reduction of adenosine A 2(A) receptors in schizophrenia. Instead, consistent with findings from animal experiments, our observation supports a role of adenosine A (2A) receptors in the molecular effects of antipsychotic drugs.
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PMID:Up-regulation of striatal adenosine A(2A) receptors in schizophrenia. 1263 74

Adenosine and dopamine receptors interact in the CNS to modulate behaviour, including sensorimotor gating. Prepulse inhibition (PPI) has been suggested to be an operational measure of sensorimotor gating. PPI and startle habituation are disrupted in patients with schizophrenia. In experimental animals, both parameters are modulated by dopaminergic and adenosine receptor agonists and antagonists. In the present study, we measured PPI and startle habituation in mice that lack functional adenosine A(2A) receptors. Startle amplitudes, startle habituation and PPI were significantly reduced in mice homozygous null for the adenosine A(2A) receptor (A(2A)(-/-)). In addition, differential effects of amphetamine and MK-801 on startle amplitude, startle habituation and PPI were observed between A(2A)(-/-) and wildtype controls. These data support the involvement of adenosine A(2A) receptors in regulation of PPI and startle habituation.
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PMID:Reduced startle habituation and prepulse inhibition in mice lacking the adenosine A2A receptor. 1290 46

Adenosine A(2A) and dopamine D(2) receptors have been shown previously to form heteromeric complexes and interact at the level of agonist binding, G protein coupling, and trafficking. Because dopamine D(2) and D(3) receptors show a high degree of sequence homology, A(2A) and D(3) receptors may also interact in a similar manner. The present studies with confocal microscopy showed that A(2A)-yellow fluorescent protein (YFP) and D(3)-green fluorescent protein 2 (GFP2) receptors colocalize in the plasma membrane. Furthermore, fluorescence resonance energy transfer (FRET) analysis demonstrated that A(2A)-YFP and D(3)-GFP2 receptors give a positive FRET efficiency and are thereby likely to exist as heteromeric A(2A)/D(3) receptor complexes. Saturation experiments with [(3)H]dopamine demonstrated that the A(2A) receptor agonist 4-[2-[[6-amino-9(N-ethyl-beta-d-ribofuranuronaminoamidosyl)-9H-purin-2-yl]amino]ethyl]benzenepropanoic acid (CGS-21680) reduced the affinity of the high-affinity agonist binding state of the D(3) receptor for [(3)H]dopamine. The A(2A) and D(2A) receptors seem to interact also at the level of G protein coupling, because the adenosine A(2A) receptor agonist CGS-21680 fully counteracted the D(3) receptor-mediated inhibition of a forskolin-mediated increase in cAMP levels. Taken together, when coexpressed in the same neuron, A(2A) and D(3) receptors seem to form A(2A)/D(3) heteromeric receptor complexes in which A(2A) receptors antagonistically modulate both the affinity and the signaling of the D(3) receptors. D(3) receptor is one of the therapeutic targets for treatment of schizophrenia, and therefore, the A(2A)/D(3) receptor interactions could provide an alternative antischizophrenic treatment.
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PMID:Adenosine A2A receptor and dopamine D3 receptor interactions: evidence of functional A2A/D3 heteromeric complexes. 1553 41


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