Transgenic overexpression of galanin in the dorsal root ganglia modulates pain-related behavior

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Much research has focused on pathways leading to opiate addiction. Pathways opposing addiction are more difficult to study but may be critical in developing interventions to combat drug dependence and withdrawal. Galanin decreases firing of locus coeruleus neurons, an effect hypothesized to decrease signs of opiate withdrawal. The current study addresses whether galanin affects morphine withdrawal signs by using a galanin agonist, galnon, that crosses the blood-brain barrier, and mice genetically engineered to under-or overexpress galanin peptide. Galnon significantly decreased morphine withdrawal signs in C57BL͞6 mice. Further, knockout mice lacking galanin showed exacerbated morphine withdrawal signs, suggesting that endogenous galanin normally counteracts opiate withdrawal. Transgenic mice overexpressing galanin in noradrenergic neurons also showed decreased morphine withdrawal signs, suggesting a possible neuroanatomical locus for these effects of galanin. Both c-fos immunoreactivity, a marker of neuronal activity, and phosphorylation of tyrosine hydroxylase at Ser-40, a marker of cAMP levels, are decreased in the locus coeruleus by galnon treatment after morphine withdrawal, suggesting a possible molecular mechanism for the behavioral effects of galanin. These studies suggest that galanin normally acts to counteract opiate withdrawal and that small molecule galanin agonists could be effective in diminishing the physical signs of withdrawal.

Section: Discussionmentioning

confidence: 61%

Section: Discussionmentioning

confidence: 99%

The neuropeptide galanin modulates behavioral and neurochemical signs of opiate withdrawal

Zachariou

Brunzell

Hawes

et al. 2003

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“…Gal-OE mice (20), which fully recapitulate the endogenous expression pattern of galanin in the intact animal and inducibly overexpress the peptide following axotomy (21), were compared with lines carrying loss-of-function mutations in the galanin peptide (22) (Gal-KO) and GalR2 (23) (GalR2-MUT). Gal-OE (line OE2) mice (20) were completely resistant to the development of any clinical disease in the EAE model, compared to strain-, age-, and sex-matched WT controls, with cumulative total EAE scores (equivalent to the area under the curve (AUC) of the mean EAE clinical score against time) of 0.1 Ϯ 0.1 vs. 26.1 Ϯ 1.9, P Ͻ 0.001 (Fig.…”

Section: Resultsmentioning

confidence: 99%

“…Details of the strain and breeding history have been previously described (20,21). In brief, galanin over expressing mice, bred to homozygosity, were generated using a Ϸ25-kb transgene containing the entire murine galanin coding region and 19.9kb of upstream sequence.…”

Section: Methodsmentioning

confidence: 99%

A role for galanin in human and experimental inflammatory demyelination

Wraith¹,

Pope²,

Butzkueven

et al. 2009

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The neuropeptide galanin is widely expressed by many differing subsets of neurons in the nervous system. There is a marked upregulation in the levels of the peptide in a variety of nerve injury models and in the basal forebrain of humans with Alzheimer's disease. Here we demonstrate that galanin expression is specifically and markedly upregulated in microglia both in multiple sclerosis (MS) lesions and shadow plaques. Galanin expression is also upregulated in the experimental autoimmune encephalomyelitis (EAE) model of MS, although solely in oligodendrocytes. To study whether the observed increase in expression of galanin in inflammatory demyelination might modulate disease activity, we applied the EAE model to a panel of galanin transgenic lines. Over-expression of galanin in transgenic mice (Gal-OE) abolishes disease in the EAE model, whilst loss-of-function mutations in galanin or galanin receptor-2 (GalR2) increase disease severity. The pronounced effects of altered endogenous galanin or GalR2 expression on EAE disease activity may reflect a direct neuroprotective effect of the neuropeptide via activation of GalR2, similar to that previously described in a number of neuronal injury paradigms. Irrespective of the mechanism(s) by which galanin alters EAE disease activity, our findings imply that galanin/GalR2 agonists may have future therapeutic implications for MS.EAE ͉ GalR2 ͉ Glia ͉ multiple sclerosis T he neuropeptide galanin (1) is widely, but by no means ubiquitously, expressed in the adult brain (2-5), and following injury there is a dramatic increase in the levels of the peptide in many neuronal subpopulations (6-8) and in the basal forebrain of patients with Alzheimer's disease (9, 10). In addition to the neuronal expression of galanin, a small number of reports have shown that the neuropeptide is also expressed by oligodendrocyte or microglial cells following cortical spreading depression (11), transient forebrain ischaemia (12) or colchicine treatment (13,14). Of note, the adult Gal-OE mice used in this study have a marked increase in neuronal galanin expression that is predominantly in the terminal fields of the hippocampus (15). Before the current study there was no evidence that galanin was expressed in non-neuronal cells in these mice.We have previously shown that kainic acid-induced cell death in the CA1 and CA3 regions of the hippocampus is markedly reduced in Gal-OE mice compared to WT controls (15). Similarly, in vitro treatment with staurosporine or glutamate induced significantly less cell death in hippocampal cultures from Gal-OE animals than in WT controls (15). In contrast, Gal-KO mice demonstrated more hippocampal cell death following in vivo and in vitro neuronal damage than WT controls (15). Furthermore the addition of exogenous galanin peptide or the GalR2/3-specific agonist Gal2-11 reduced the amount of cell death when co-administered with either glutamate or staurosporine in WT primary hippocampal cultures (15). We have recently extended these findings by demonstrating that organo...

“…Cck and Vip, as well as Adcyap1, have been proposed as promising therapeutic targets for the treatment of neuropathic pain (49) and have been listed in other published microarray datasets from stress and depression studies (10,43,50) (Table S2). Also regulated by DMI in Rgs9KO mice were the peptides oxytocin, which has been implicated in antinociceptive mechanisms (51), and galanin (Gal), which has a profound role in nerve injury (52,53) and neuropathic pain-induced motivational changes (54).…”

Section: Discussionmentioning

confidence: 99%

RGS9-2–controlled adaptations in the striatum determine the onset of action and efficacy of antidepressants in neuropathic pain states

Mitsi

Terzi

Purushothaman

et al. 2015

The striatal protein Regulator of G-protein signaling 9-2 (RGS9-2) plays a key modulatory role in opioid, monoamine, and other G-protein-coupled receptor responses. Here, we use the murine spared-nerve injury model of neuropathic pain to investigate the mechanism by which RGS9-2 in the nucleus accumbens (NAc), a brain region involved in mood, reward, and motivation, modulates the actions of tricyclic antidepressants (TCAs). Prevention of RGS9-2 action in the NAc increases the efficacy of the TCA desipramine and dramatically accelerates its onset of action. By controlling the activation of effector molecules by G protein α and βγ subunits, RGS9-2 affects several protein interactions, phosphoprotein levels, and the function of the epigenetic modifier histone deacetylase 5, which are important for TCA responsiveness. Furthermore, information from RNA-sequencing analysis reveals that RGS9-2 in the NAc affects the expression of many genes known to be involved in nociception, analgesia, and antidepressant drug actions. Our findings provide novel information on NAc-specific cellular mechanisms that mediate the actions of TCAs in neuropathic pain states.desipramine | duloxetine | HDAC5 | spared nerve injury | gene expression R egulator of G-protein signaling 9-2 (RGS9-2) is an intracellular modulator of G-protein-coupled receptor (GPCR) function, which is expressed in medium spiny neurons and cholinergic interneurons of the striatum (1, 2). RGS9-2 influences the magnitude and time course of GPCR signaling by promoting GTPase activity of the Gα subunit and by preventing activation of Gα effectors (3). This modulation can also influence the duration of interactions between the Gβγ subunits and their effector molecules. In addition to Gα subunits, RGS9-2 interacts with several scaffolds and signal transduction proteins that affect its function, expression, and cellular localization. Interactions with the Gβ5 subunit and the adaptor protein R7BP determine the stability and cellular localization of RGS9-2, respectively (3, 4). Several recent studies have provided information on the regulation and function of RGS9-2 complexes in the striatum and how these complexes affect pharmacologic responses (2, 5, 6). In particular, RGS9-2 has been shown to modulate the actions of various psychotropic, antiparkinsonian, neuroleptic, and opiate analgesic drugs (1, 7). The nucleus accumbens (NAc) is a striatal brain region that is a major site of antidepressant drug action (8). Recent studies provided information on signal transduction events triggered by tricyclic antidepressants (TCAs) in NAc neurons and identified several second messengers, transcription factors, and epigenetic molecules involved in their therapeutic actions (9-11). TCAs, such as desipramine (DMI) and nortriptyline (NTL), and selective serotonin/norepinephrine reuptake inhibitors (SNRIs) have also been used to treat neuropathic pain, a complex chronic disorder that is highly comorbid with anxiety and depression (12, 13) and is characterized by thermal hyperalgesia, mech...