ABSTRACT:
Nair2015 - Interaction between
neuromodulators via GPCRs - Effect on cAMP/PKA signaling (D1
Neuron)
This model is described in the article:
Sensing Positive versus
Negative Reward Signals through Adenylyl Cyclase-Coupled GPCRs
in Direct and Indirect Pathway Striatal Medium Spiny
Neurons.
Nair AG, Gutierrez-Arenas O,
Eriksson O, Vincent P, Hellgren Kotaleski J.
J. Neurosci. 2015 Oct; 35(41):
14017-14030
Abstract:
Transient changes in striatal dopamine (DA) concentration
are considered to encode a reward prediction error (RPE) in
reinforcement learning tasks. Often, a phasic DA change occurs
concomitantly with a dip in striatal acetylcholine (ACh),
whereas other neuromodulators, such as adenosine (Adn), change
slowly. There are abundant adenylyl cyclase (AC) coupled GPCRs
for these neuromodulators in striatal medium spiny neurons
(MSNs), which play important roles in plasticity. However,
little is known about the interaction between these
neuromodulators via GPCRs. The interaction between these
transient neuromodulator changes and the effect on cAMP/PKA
signaling via Golf- and Gi/o-coupled GPCR are studied here
using quantitative kinetic modeling. The simulations suggest
that, under basal conditions, cAMP/PKA signaling could be
significantly inhibited in D1R+ MSNs via ACh/M4R/Gi/o and an
ACh dip is required to gate a subset of D1R/Golf-dependent PKA
activation. Furthermore, the interaction between ACh dip and DA
peak, via D1R and M4R, is synergistic. In a similar fashion,
PKA signaling in D2+ MSNs is under basal inhibition via
D2R/Gi/o and a DA dip leads to a PKA increase by disinhibiting
A2aR/Golf, but D2+ MSNs could also respond to the DA peak via
other intracellular pathways. This study highlights the
similarity between the two types of MSNs in terms of high basal
AC inhibition by Gi/o and the importance of interactions
between Gi/o and Golf signaling, but at the same time predicts
differences between them with regard to the sign of RPE
responsible for PKA activation.Dopamine transients are
considered to carry reward-related signal in reinforcement
learning. An increase in dopamine concentration is associated
with an unexpected reward or salient stimuli, whereas a
decrease is produced by omission of an expected reward. Often
dopamine transients are accompanied by other neuromodulatory
signals, such as acetylcholine and adenosine. We highlight the
importance of interaction between acetylcholine, dopamine, and
adenosine signals via adenylyl-cyclase coupled GPCRs in shaping
the dopamine-dependent cAMP/PKA signaling in striatal neurons.
Specifically, a dopamine peak and an acetylcholine dip must
interact, via D1 and M4 receptor, and a dopamine dip must
interact with adenosine tone, via D2 and A2a receptor, in
direct and indirect pathway neurons, respectively, to have any
significant downstream PKA activation.
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