Lecture_15_-_Atypical_Neurotransmitters

Transcribed when c fos or c jun binds release is

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transcribed when c-fos or c-jun binds) Release is triggered by depolarization Degradation occurs through proteolytic degradation or binding to truncated receptors which limits their diffusion All growth factors elicit their biological effects via the stimulation of RTKs Neurotrophins : exclusively in nervous system, small and dimerize to form biologically active signaling molecules; bind to the promiscuous p75 receptor and to the Tropomycin/Tyrosine receptor kinase ( Trk) family of RTKs which stimulate MAPK pathways
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Trk Receptors Limited to neurons Kinase domains are highly conserved; differ in their extracellular domains When ligand binds, the ligand-receptor complex internalizes and is then transported to the cell body by axonal transport
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P75 Receptors Enhance neurotrophin activity • Equal affinity for all neurotrophins • Can cause TrK receptors to be more sensitive to their neurotrophin ligands • May make TrKA more selective for NGF and TrKB for BDNF Oppose neurotrophin activity • Can trigger apoptosis (cell death)
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Growth Factors and Disease • Decreased expression of BDNF may play a role in depression • Leads to decreased neurogenesis in the hippocampus, decreased dendritic spine density • SSRIs may work in part by increasing BDNF expression (by stimulation of the cAMP pathway)
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Treating Disease with Growth Factors Neurodegenerative diseases, such as Parkinson's, may be good candidates for treatment by growth factors Problems: •Growth factors are large molecules, difficult to get into the cns by systemic administration •Growth factors can be active in many different tissues outside of the cns, which leads to many side effects Solutions: •Intracranial dosing route – target specific brain regions •Viral vectors to increase the expression of growth factors •Develop small molecules that work as agonists at TrK receptors
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Purinergic Transmitters Historically, not considered probable mediators of neurotransmission because of their role in metabolism and as building blocks for DNA and RNA Now know they fit the criterion for a neurotransmitter: Concentrated in nerve terminals Released in response to neuronal stimulation Activate receptors to produce a biological effect Purines : ring-structured basic molecules that include adenine and guanine Puringeric transmitters : nucleoside and nucleotide derivatives of purine bases Major purinergic transmitters are: Adenosine, ATP and adenine dinucleosides (ApnA; n=# phosphates between the 2 adenosine molecules)
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Storage and release: ATP and ApnA are stored in small synaptic vesicles and released in response to action potentials (i.e., release is Ca2+-dependent) Often co-localized with
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transcribed when c fos or c jun binds Release is triggered...

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