Opioid receptors dor opioid receptor for vas eferens

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-opioid receptors (DOR) - opioid receptor . for vas eferens Subtypes are 1, 2 Enkephalin has high affinity for DOR DOR -mediated activity does not appear to be involved in drug dependence But DORs mediate reward pathway Exist as dimers – agonist influenced High concentrations found in hypothalamus, raphe magnus, pain complex in the spinal cord, pituitary
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-opioid receptors (KOR) Named for etocyclazocine Subtypes are 1, 3 Dynorphin has high affinity Located primarily in spinal cord and nucleus accumbens . receptor stimulation may be able to produce analgesia without euphoria therefore less abuse potential Kappa aversion: KOR agonists can produce dysphoria and psychotomimetic effects ; this suggests that addiction may be due to a dysfunctional KOR system Aversion mechanism: KOR stimulation of certain neuronal population in the n. accumbens may cause aversion
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Lecture 9b Objectives: Growth Factors Define “growth factors” and contrast with “neurotrophin” Describe the intracellular signaling cascade(s) activated by the stimulation of Trk receptors Match each neurotrophin with its appropriate Trk receptor and outline how the interaction of each neurotrophin with its Trk receptor leads to effects upon gene transcription List the major superfamilies of growth factors and provide examples for each
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Peptide Growth Factors Proteins that stimulate cellular proliferation and promote cell survival Often referred to as “ neurotrophic factors ” or neurotrophins (act exclusively in the nervous system) NGF (nerve growth factor) was the first to be characterized Some act only during restricted periods of development; others act throughout life Synthesized by a wide variety of cell types incl. neurons, glia Secreted into the extracellular fluid, diffuse and then act either on other cells (paracrine) or on releasing cell (autocrine) At least 15 different growth factors promote the development and survival of neurons Growth factors can also regulate the synthesis and release of other neurotransmitters (contribute to synaptic plasticity)
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Varieties of Growth Factors 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 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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