1. Describe the general steps involved in synaptic transmission.
• action potential enters pre-synaptic terminal
• AP activates voltage dependent calcium channels
• Ca2+ ions enter the cell
• Increased Intracellular [Ca2+]
• binding of vesicles to presynaptic membrane
• release of neurotransmitter into synaptic cleft
• binding to postsynaptic receptors,
• activation of ion gate sodium channels
• Post-synaptic potential > AP
• Removal from synaptic cleft by enzymatic degradation or re-uptake across the
plasma membrane
2. Describe the synthesis and degradation steps of the following neurotransmitters:
a. Acetylcholine
• Synthesized by ChAT
• Packaged into vesicles by VAChT
• Hydrolysis by acetylcholinesterase into acetate and choline
• Shunting into presynaptic terminals by choline transport protein
b. GABA
• Synthesized from glutamate by GAD
• Packaged by VGAT
• Removal from synaptic cleft by high affinity GABA transporter
c. Dopamine
• Synthesized by Tyrosine Hydroxylase
• Packaged through Vesicular Monoamine Transporter
• reuptake by DAT and/or degradation by MAO or CoMT
3. What are the criteria for a specific substance to be classified as a neurotransmitter?
1) synthesized in neuron, 2) stored in nerve terminal, 3) released in quantities sufficient
to affect postsynaptic cell, 4) exogenous application mimics action, 5) mechanism for
removal, 6) the presence and use of specific pharmacological blockers and agonists.
4. What are the major structural and functional similarities and differences between
ionotropic and metabotropic neurotransmitter receptors? What are the advantages of
each? Provide two examples of each type of receptor
STRUCTURAL/FUNCTIONAL SIMILARITIES: Both are transmembrane proteins, both bind
transmitters (ligand gated), both bind transmitter on the extracellular side of the
receptor, and both act as transducers of information from the presynaptic cell.
