G-protein coupled receptors interact to provide additional regulatory mechanisms for neurotransmitter signaling. Adenosine A(2A) receptors are expressed at a high density in striatal neurons, where they closely interact with dopamine D₂ receptors and modulate effects of dopamine and responses to psychostimulants. A(2A) receptors are expressed at much lower densities in other forebrain neurons b...

A cDNA clone is described that encodes a novel G-protein-coupled dopamine receptor (DopR99B) expressed in Drosophila heads. The DopR99B receptor maps to 99B3-5, close to the position of the octopamine/tyramine receptor gene at 99A10-B1, suggesting that the two may be related through a gene duplication. Agonist stimulation of DopR99B receptors expressed in Xenopus oocytes increased intracellular...

The classical dopamine hypothesis of schizophrenia postulates a hyperactivity of dopaminergic transmission at the D(2) receptor. We measured in vivo occupancy of striatal D(2) receptors by dopamine in 18 untreated patients with schizophrenia and 18 matched controls, by comparing D(2) receptor availability before and during pharmacologically induced acute dopamine depletion. Acute depletion of i...

In primates, CB(1) cannabinoid receptor agonists produce sedation and psychomotor slowing, in contrast to behavioral stimulation produced by high doses of dopamine receptor agonists. To investigate whether dopamine agonists attenuate the sedative effects of a cannabinoid agonist in monkeys, we compared the effects of D(1) or D(2) dopamine receptor agonists on spontaneous behavior in three to si...

Background Increased locomotor activity in response to the same stimulus is an index of behavioral sensitization observed in preclinical models of drug addiction and compulsive behaviors. Repeated administration of quinpirole, a D2/D3 dopamine agonist, induces locomotor sensitization. This effect is potentiated and accelerated by co-administration of U69593, a kappa opioid receptor agonist. The...

previous studies have shown that ascorbic acid (aa) plays a crucial role in mammalian brain as avitamin and neuronal modulator. there is increasing evidence indicating that dopaminergic system and aacould affect learning and memory processes. in addition, vitamin c acts as a dopamine antagonist in thebrain. the aim of the present study was to evaluate the intra-hippocampal co-administration of ...

objective: curcumin is a major constituent of turmeric and influences many functions of the brain. in the present study, we investigated the effect of curcumin on yawning induced by apomorphine in rats. materials and methods: curcumin administered orallyfor 10 consecutive days. yawning was induced by subcutaneous (s.c.) injection of apomorphine (a dopamine receptor agonist) and the number of ya...

Adenosine receptors modulate dopaminergic function by regulating dopamine release in presynaptic neurons and intracellular signaling in postsynaptic striatal neurons. To investigate how adenosine impinges on the action of dopamine in feeding and locomotion, genetically altered, dopamine-deficient mice were treated with adenosine receptor antagonists. Acute administration of the nonselective ade...

adenosine acts as neuromodulator in the brain, which its involvement in a wide range of brain processes and diseases has been studied, such as epilepsy, sleep, anxiety, panic disorder, alzheimer’s disease, parkinson’s disease and schizophrenia. adenosine receptors have been detected: a1r, a2ar (a2ar), a2br, and a3r. a1r and a2r inhibit camp production, while a2ar and a2br stimulate camp product...

Given the complex interactions between dopamine D1 and glutamate NMDA receptors in the striatum, we investigated the role of these receptors in transporter-mediated GABA release from cultured medium spiny neurons of rat striatum. Like NMDA receptor-mediated [(3)H]-GABA release, that induced by prolonged (20 min) dopamine D1 receptor activation was enhanced on omission of external calcium, was a...