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Neurobiology questions

1. Two types of GABA receptors have been identified. The GABA(a) receptor is an ion channel permeable to CL-; and the GABA(b) receptor is a G-protein-couple receptor (activates a second messenger cascadein the postsynaptic cell) which causes K+ selective channels to open. What effect would the activation of GABA(b) receptors have on the membrane potential of the postsynaptic cell? Explain your answer?

2. Consider an excitatory synapse on the soma of a neuron and another excitatory synapse on the tip of a dendrite. Which of the two would be more effective in evoking action potentials in the synaptic neuron? (In other words, does the expression "Location, location, location" apply to neurons? Explain your answer.

Solution Preview

1. Let's break this down:
GABA receptors are inhibitory neurotransmitters

GABA(a) transports Cl- into or out of the cell (the direction depends on the Cl- concentration)
GABA(b) transports K+ into or out of the cell (the direction depends on the K+ concentrations, typically potassium is higher inside the cell)

The resting potential of the cell is -70mV on the inside (meaning there are more negative charges inside the cell; the outside potential is 70mV). When GABA(b) is selectively activated it drives the export of K+ out of the cell ...