Characterization of RGS14 in the Adult Mouse Brain and its Role in Limiting Cocaine-Induced Behavioral Adaptations Pubblico
Bramlett, Sara (Fall 2024)
Abstract
Regulator of G protein signaling 14 (RGS14) is a multifunctional signaling protein that acts as a natural suppressor of synaptic plasticity, particularly in the hippocampus. Previously, RGS14 was found primarily in the postsynaptic dendrites of pyramidal neurons in hippocampal area CA2, but more recent studies have shown that RGS14 is expressed in multiple neuron populations throughout the hippocampus (CA1 and CA2), caudate nucleus, putamen, globus pallidus, substantia nigra, and amygdala. Additionally, RGS14 is present in limbic regions associated with reward behavior and addiction, such as the central amygdala and nucleus accumbens (NAc). Here, we provide comprehensive mapping of RGS14 in the adult mouse brain, revealing its widespread expression. Strong RGS14 staining is observed in neuron populations of the hippocampal formation, amygdala, septum, bed nucleus of the stria terminalis, and NAc, as well as in axon fiber tracts, including the dorsal fornix and fimbria. These findings suggest that RGS14 modulates core cognitive functions such as sensory perception, emotion, memory, and motivation by regulating plasticity in these regions.
Further, we explored the role of RGS14 in cocaine-induced plasticity in emotional-motivational circuits. Using immunofluorescence and dopamine receptor reporter mice, we found that RGS14 is localized to neurons expressing D1 and D2 dopamine receptors in NAc neurons and is upregulated in the NAc of mice with chronic cocaine history. RGS14-deficient mice exhibited significantly enhanced cocaine-induced locomotor sensitization, conditioned place preference, and conditioned locomotor activity compared to wild-type controls. These results suggest that endogenous RGS14 suppresses cocaine-induced neuroplasticity in emotional and motivational circuits, acting as a protective factor against maladaptive changes that contribute to addiction. Together, these findings reveal that RGS14 plays a key role in regulating both normal and drug-induced plasticity in regions of the brain that govern cognition, motivation, and addiction-related behaviors.
Table of Contents
Table of Contents
Page
Chapter 1: Introduction
1.1 Regulator of G protein Signaling 14: structure and binding partners……………..1
1.2 RGS14 regulation of postsynaptic signaling and plasticity……………………….3
1.3 Tissue distribution of RGS14………………………………………….…………..4
1.4 RGS14 in the limbic system………………………………………………………7
1.5 RGS14 in the basal ganglia………………………………………………………11
1.6 Addiction pathology and possible roles of RGS14……………………………….13
1.7 Research objectives………………………………………………………………18
Chapter 2: Methods
2.1 Subjects…………………………………………………………………………..20
2.2 Immunohistochemistry…………………………………………………………..20
2.3 Fluorescent imaging and image processing……………………………………...22
2.4 Assessment of relative protein levels…………………………………………….23
2.5 Drugs……………………………………………………………………………..24
2.6 Locomotor sensitization……………………………………………………….…24
2.7 Conditioned place preference……………………………………………………25
2.8 Statistics………………………………………………………………………….26
Chapter 3: Characterization of RGS14 in the adult mouse brain
3.1 Heat atlas of RGS14 protein……………………………………………………..28
3.2 Olfactory areas…………………………………………………………………...33
3.3 Isocortex……………………………………………………………………….…33
3.4 Septal regions…………………………………………………………………….42
3.5 Amygdaloid complex & extended amygdala…………………………………….43
3.6 Hippocampal formation………………………………………………………….44
3.7 Basal ganglia and midbrain……………………………………………….……...45
3.8 Discussion…………………………………………………………………….….59
3.8.1. RGS14 in the hippocampal formation, septal regions, and basolateral amygdala…………………………………………………………………..60
3.8.2. RGS14 in the extended amygdala………………………………………... 63
3.8.3. RGS14 in the basal ganglia………………………………………………..65
3.8.4. Caveats and limitations……………………………………………………66
3.8.5. Conclusions………………………………………………………………..68
Chapter 4: Endogenous RGS14 suppresses cocaine-induced emotionally-motivated behaviors in female mice
4.1 RGS14 localizes to D1R- and D2R-expressing cells in the nucleus accumbens...69
4.2 RGS14 is upregulated following cocaine challenge in the nucleus accumbens of mice with a chronic cocaine history……………………………………………..71
4.3 Enhanced locomotor sensitization to cocaine in RGS14-KO mice……………...71
4.4 RGS14 loss increases the expression of cocaine-induced locomotor sensitization……………………………………………………………………...74
4.5 RGS14 loss alters the temporal dynamics of cocaine-induced locomotor activation………………………………………………………………………...75
4.6 RGS14 loss augments the magnitude and duration of cocaine-conditioned place preference………………………………………………………………………..81
4.7 RGS14 loss augments the magnitude and duration of cocaine-conditioned locomotor hyperactivity……………………………………………………...…..82
4.8 RGS14 regulates cocaine-conditioned place preference and cocaine-conditioned locomotor activation through dissociable mechanisms………………………….84
4.9 Cocaine conditioning overcomes stronger inherent place aversion in RGS14-KO mice…………………………………………………………………….………...84
4.10 RGS14 and pERK colocalize in distinct neurons in the nucleus accumbens and extended amygdala following cocaine………………………......……………….89
4.10.1. RGS14 and pERK colocalize in patches in nucleus accumbens core and shell… …………………………………………………………………....90
4.10.2. RGS14 and pERK colocalize in dorsal BNSTov and BNSTju……………91
4.10.3. RGS14 and pERK colocalize in the lateral-capsular central amygdala…...96
4.11 Discussion………………………………………………………………………..99
4.11.1. RGS14 actions in the nucleus accumbens and regulation of locomotor activity…………………………………………………………………..…99
4.11.2. RGS14 actions outside of the nucleus accumbens and cocaine-conditioned place preference……………………………………………….………….101
4.11.3. Dissociation of RGS14 actions on cocaine-induced limbic and motor system adaptations………………………………………………….…………….103
4.11.4. RGS14 in addiction and anxiety in women and girls……………….……103
4.11.5. Caveats and limitations…………………………………………………..105
4.11.6. Conclusions………………………………………………………………106
Chapter 5: Final discussion, conclusions, and future directions
5.1 Overview of brain RGS14 expression and possible functional implications..107
5.2 Possible differential regulation of signaling in nucleus accumbens D1- and D2-MSN……………………………………………………………108
5.3 Implications for RGS14 in human disease and future directions……………111
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