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Lecture_15_-_Atypical_Neurotransmitters

Classical neurotransmitters and even found in same

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classical neurotransmitters and even found in same vesicles as classic neurotransmitters Adenosine is released from non-vesicular stores by: Bidirectional transporters Membrane-bound ectodiphosphohydrolase metabolizes ATP to adenosine; thus, the release of ATP can be a source of extracellular adenosine Transporters: 2 major nucleoside transporters Equilibrative Nucleoside Transporters (ENT1-4): mediate both efflux and influx Concentrative Nucleoside Transporters (CNT1-3): mediate Na+-dependent influx -chemotherapeutic (gemcitabine) and antiviral drugs (AZT) target these transporters
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Receptors: 2 subfamilies: P1 and P2 P1 (incl. A1, A2A, A2B, A3): G-protein coupled A1 has highest expression in CNS and highest affinity for adenosine (activation sedation and anxiolysis; inhibition (e.g., by caffeine) arousal and anxiety A2A highly concentrated in striatal structures and co-localized with dopamine receptors (agonists inhibit D2 activated behaviors; antagonists mimic D2 activated behaviors) A2B is ubitiquitous in body A3 in low levels in the brain
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A2A and D2 Receptor Interaction A2A stimulates the cAMP pathway, whereas D2 inhibits it They also interact in another way. A2A and D2 form a heterodimer, which reduces D2 recognition, coupling and signaling
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