Question

Identify the mechanisms that could produce increased release probability of GABA in the given circuit.

a) Phosphorylation by PKA of the mu opioid receptors on the GABA terminals increases the constitutive activity of the mu opioid receptors.
b) Phosphorylation by PKA of a Calcium channel increases the number of calcium channels in the GABA terminals.
c) Phosphorylation by PKA of the GABA-A receptors in the GABA neuron increases their affinity for GABA.
d) Phosphorylation by PKA of the mu opioid receptors promotes their desensitization.
e) Phosphorylation by PKA of mu opioid receptors on the GABA terminals switches their coupling to Go.

Answer 1

Increased release probability of GABA can be a result of PKA-mediated phosphorylation that increases calcium channels at GABA terminals, facilitating greater calcium influx and GABA release when neurons are active.

Step-by-step explanation:

The mechanisms that could produce increased release probability of GABA in the given circuit include the phosphorylation of various proteins by protein kinase A (PKA). Phosphorylation is a common way of regulating protein function and can lead to different outcomes depending on the target. Option b stands out as a mechanism that could increase GABA release probability at the terminals: phosphorylation by PKA of a Calcium channel increases the number of calcium channels in the GABA terminals. Increased calcium channel numbers can lead to more calcium influx when the neurons are active, which in turn can increase the probability of GABA-containing vesicles fusing with the presynaptic membrane and releasing their neurotransmitter content.