NEUROTRANSMITTERS AND NEUROMODULATORS

• mediates communication within neuron-to-neuron or neuron-to effector organ

  neurotransmitter
• glutamate

  small molecule transmitters
• γ-aminobutyric acid [GABA]


  small-molecule transmitters
• norepinephrine

  small molecule transmitters
• dopamine

  small molecule transmitters
• neuropeptides

  large molecule transmitters
• substance P

  large molecule transmitters
• enkephalin

  large molecule transmitters
• nitric oxide (NO)

  gas transmitters
• receptors for many neurotransmitters are located on both presynaptic and postsynaptic element
• presynaptic receptor, inhibits further release of the transmitter, providing feedback control


  autoreceptor
• ligand is a chemical other than the transmitter released by the nerve ending on which the receptor is located

  heteroreceptor
• receptors are concentrated in clusters on the postsynaptic membrane close to the endings of neurons that secrete the neurotransmitters specific for them
• loss of responsiveness only to the ligand and maintained responsiveness of the cell to other ligands

  homologous
• cell becomes unresponsive to other ligands as well

  heterologous
• Process in which neurotransmitters are rapidly transported from the synaptic cleft back into the cytoplasm of the neurons are released called reuptake
• involves a high-affinity, Na+ -dependent membrane transporter

  reuptake
• After release of norepinephrine into the synaptic cleft, it is rapidly routed back into the sympathetic nerve terminal by a norepinephrine transporter (NET).
• A portion of the norepinephrine that re-enters the neuron is sequestered into the synaptic vesicles through the vesicular monoamine transporter (VMAT)
• Maybe excitatory or inhibitory

  acetylcholine
• Created by: Choline Acetyl- transferase from Acetyl CoA and Choline


  acetylcholine
• Degraded by: Acetylcholinesterase into Acetate and Choline (1⁄2 of which will undergo reuptake)


  acetylcholine
• Triggers REM sleep

  acetylcholine
• decreased levels in Huntington’s dementia and Alzheimer’s dementia

  acetylcholine
• Found in the locus ceruleus of pons


  norepinephrine
• NOREPINEPHRINE

  • NeuroMODULATOR in the CNS and NeuroTRANSMITTER in the PNS synthesized INSIDE synaptic vesicles
• NOREPINEPHRINE

  • HALF-LIFE: 2 MINUTES (short compared to renin, aldosterone, corticosterone, and DHEA)
• Primary NT from post-ganglionic sympa neurons

  norepinephrine
• for arousal/wakefulness

  norepinephrine
• Secreted mainly by the adrenal medulla greater Beta-2 action than NE


  epinephrine
• Relieve effects of bee sting by decreasing contraction of airway smooth muscles


  epinephrine
• Secreted in the substantia nigra (fine-tunes movement)


  dopamine
• Also secreted by the hypothalamus (PIF or PIH) to inhibit prolactin


  dopamine
• D1 Receptor: activates adenylate cyclase using Gs protein; D2: inhibits adenylate cyclase using G1 protein


  dopamine
• can be due to abnormalities in the prefrontal lobes, frontal lobes and limbic system (hippocampus)


  Schizophrenia
• Found in the median raphe of the brain stem, from tryptophan, converted to melatonin


  serotonin
• low levels association with depression


  serotonin
• NO synthase converts Arginine to citrulline and NO
• Permeant gas, inhibitory NT, vasodilator


  nitric oxide
• • Spinal cord main inhibitory NT;


  glycine