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Background Selective serotonergic reuptake inhibitors, including fluoxetine (FLX), are the most commonly used for the treatment of major depression. However, they are effective for remission in only 30% of patients. Recently, we observed that Galanin (1-15) [GAL(1-15)] enhanced the antidepressant effects of FLX in naïve animals, suggesting a new augmentation strategy in depression. Methods We have analyzed in an animal model of depression, the olfactory bulbectomy (OBX) rats, the effect of GAL(1-15) on FLX-mediated responses in the forced swimming test and the sucrose preference test and the involvement of GAL receptor 2 with its antagonist, M871. We have also studied the corticosterone levels in OBX after the coadministration of GAL(1-15) with FLX. Moreover, we studied whether the effects of GAL(1-15) on FLX actions were mediated via auto- and heteroreceptor 5-HT1A (5-HT1AR), analyzing the binding characteristics, mRNA levels, and functionality of 5-HT1AR in the dorsal hippocampus. Results GAL(1-15) enhances the antidepressant-like effects induced by FLX in OBX animals in the forced swimming test and the sucrose preference test. The involvement of the GALR2 was demonstrated with M871. Importantly, the mechanism underlying the GAL(1-15)/FLX interactions in the OBX animals involves the 5-HT1AR in the hippocampus at the plasma membrane (increase of affinity and density of 5HT1AR in the DG) and transcriptional (increase of 5HT1AR mRNA levels in DG and CA1) levels. Besides, the coadministration of GAL(1-15) and FLX also reduced OBX-increased corticosterone levels. Conclusions The results open the possibility to use GAL(1-15) in combination with FLX as a novel strategy for the treatment of depression.

Alcohol Use Disorder (AUD) is among the most prevalent mental illnesses, and due to the low efficacy of the current medication, it is essential to find new biological targets that could modulate alcohol consumption. Since Galanin (1−15) [GAL(1−15)] produces a loss of motivational behaviour by an artificial reinforcer and decreases the preference an alcohol consumption in a voluntary alcohol intake, we have studied the role of GAL(1−15) in alcohol-seeking behaviour and the involvement of the corticomesolimbic system as well as the role of GAL(1−15) in context-induced alcohol relapse. In rats, we have studied GAL(1−15)-effects on alcohol-seeking in self-administration, in fixed-ratio (FR1) and progressive-ratio (PR), and the involvement of GAL receptors using siRNA GALR1 or GALR2 knockdown animals. We have analysed the transcriptional changes of C-Fos, dopamine receptors, GAL receptors and 5HT1A receptors in the corticomesolimbic system. Also, we have examined the effect of GAL(1−15) in context-induced alcohol relapse. GAL(1−15) substantially reduced alcohol-seeking behaviour in the operant self-administration model in an FR1 protocol and at the breaking point in a PR schedule. GALR1and GALR2 were involved in these effects, as indicated by the analysis by GALR2 antagonist and GALR1 and GALR2 knockdown animals. Notably, the mechanism of GAL(1−15)-mediated actions involved changes in C-Fos, Dopamine receptors and 5HT1A expression in the ventral tegmental area, accumbens nucleus and prefrontal cortex. Significantly, GAL(1−15) reduced the context-induced alcohol relapse. These results open up the possibility to use GAL(1−15) as a novel strategy in AUD. This work was supported by grants awarded by Spanish Ministry of Economy PID2020-114392RB-100, PDC2021-121566-100 and by Junta de Andalucía P20-00026-R and PI-0083-2019. Partial funding for open access charge: Universidad de Málaga

Selective 5-HT reuptake inhibitor antidepressants (SSRIs) are the first choice in major depressive disorder (MDD), but 50% of affected patients do not show improvement. Galanin(1-15) [GAL(1-15)] enhanced Fluoxetine antidepressant-like effects in an animal model of depression, the olfactory bulbectomy (OBX), however, further detailed analysis of GAL(1-15) effects as augmentation treatment in OBX rats are needed. In OBX rats, we analysed the effect of GAL(1–15) on Escitalopram (ESC)-mediated responses in behavioural tests related to despair. We studied whether GAL(1–15) effects involved 5-HT1AR using an in vivo model siRNA 5-HT1A knockdown rats. Moreover, we analysed by immunohistochemistry the expression of the immediate-early gene c-Fos (c-Fos IR) after the administration of GAL(1-15)+ESC in OBX rats in several nuclei involved in MDD. GAL(1-15) enhances the antidepressant-like effects of ESC, and the GALR2 antagonist M871 blocked GAL(1-15) mediated actions. The downregulation of 5-HT1AR by siRNA was sufficient to block GAL(1-15) effects. Our immunohistochemistry and principal component analysis (PCA) analysis suggest that two functional networks are involved in these effects, one includes the lateral (LHb) and medial (mHb) habenula, dorsal raphe (DR) and ventral tegmental area (VTA), and the other consists of the dentate gyrus (DG), and prefrontal cortex (PFC). The results open up the possibility of using GAL(1-15) in combination with SSRIs as a novel strategy for treating MDD.

Oxidative distress and mitochondrial dysfunction, are key factors involved in the pathophysiology of Parkinson's disease (PD). The pleiotropic hormone insulin-like growth factor II (IGF-II) has shown neuroprotective and antioxidant effects in some neurodegenerative diseases. In this work, we demonstrate the protective effect of IGF-II against the damage induced by 1-methyl-4-phenylpyridinium (MPP+) in neuronal dopaminergic cell cultures and a mouse model of progressive PD. In the neuronal model, IGF-II counteracts the oxidative distress produced by MPP + protecting dopaminergic neurons. Improved mitochondrial function, increased nuclear factor (erythroid-derived 2)-like2 (NRF2) nuclear translocation along with NRF2-dependent upregulation of antioxidative enzymes, and modulation of mammalian target of rapamycin (mTOR) signalling pathway were identified as mechanisms leading to neuroprotection and the survival of dopaminergic cells. The neuroprotective effect of IGF-II against MPP + -neurotoxicity on dopaminergic neurons depends on the specific IGF-II receptor (IGF-IIr). In the mouse model, IGF-II prevents behavioural dysfunction and dopaminergic nigrostriatal pathway degeneration and mitigates neuroinflammation induced by MPP+. Our work demonstrates that hampering oxidative stress and normalising mitochondrial function through the interaction of IGF-II with its specific IGF-IIr are neuroprotective in both neuronal and mouse models. Thus, the modulation of the IGF-II/IGF-IIr signalling pathway may be a useful therapeutic approach for the prevention and treatment of PD., Graphical abstract Image 1, Highlights • IGF-II hampers oxidative damage and promotes survival in a cellular model of PD. • IGF-II avoids mitochondrial damage in dopaminergic cells in a model of PD. • IGF-II receptor mediates the neuroprotective effect of IGF-II in a cellular model of PD. • IGF-II prevents nigrostriatal degeneration and inflammation in a mice model of PD. • IGF-II prevents behavioural dysfunction in a mice model of PD.

Alcohol consumption is considered a major risk factor for disease and mortality worldwide. In the absence of effective treatments in alcohol use disorders, it is important to find new biological targets that could modulate alcohol consumption. We tested the role of the N-terminal galanin fragment (1-15) [GAL(1-15)] in voluntary ethanol consumption in rats using the two-bottle choice paradigm as well as compare the effects of GAL(1-15) with the whole molecule of GAL. We describe for the first time that GAL(1-15), via central mechanisms, induces a strong reduction in preference and ethanol consumption in rats. These effects were significantly different than GAL. GAL receptor (GALR) 2 was involved in these effects, because the specific GALR2 antagonist M871 blocked GAL(1-15) mediated actions in preference and ethanol intake. Importantly, the mechanism of this action involves changes in GALR expression and also in immediate-early gene C-Fos and receptors-internalization-related gene Rab5 in the striatum. The relevance of the striatum as a target for GAL(1-15) was supported by the effect of GAL(1-15) on the locomotor activity of rats after ethanol administration. These results may give the basis for the development of novel therapeutics strategies using GAL(1-15) analogues for the treatment of alcohol use disorders in humans.

Insulin-like growth factor-II (IGF-II) is a naturally occurring hormone that exerts neurotrophic and neuroprotective properties in a wide range of neurodegenerative diseases and ageing. Accumulating evidence suggests that the effects of IGF-II in the brain may be explained by its binding to the specific transmembrane receptor, IGFII/M6P receptor (IGF-IIR). However, relatively little is known regarding the role of IGF-II through IGF-IIR in neuroprotection. Here, using adult cortical neuronal cultures, we investigated whether IGF-II exhibits long-term antioxidant effects and neuroprotection at the synaptic level after oxidative damage induced by high and transient levels of corticosterone (CORT). Furthermore, the involvement of the IGF-IIR was also studied to elucidate its role in the neuroprotective actions of IGF-II. We found that neurons treated with IGF-II after CORT incubation showed reduced oxidative stress damage and recovered antioxidant status (normalized total antioxidant status, lipid hydroperoxides and NAD(P) H:quinone oxidoreductase activity). Similar results were obtained when mitochondria function was analysed (cytochrome c oxidase activity, mitochondrial membrane potential and subcellular mitochondrial distribution). Furthermore, neuronal impairment and degeneration were also assessed (synaptophysin and PSD-95 expression, presynaptic function and FluoroJade B® stain). IGF-II was also able to recover the long-lasting neuronal cell damage. Finally, the effects of IGF-II were not blocked by an IGF-IR antagonist, suggesting the involvement of IGF-IIR. Altogether these results suggest that, in or model, IGF-II through IGF-IIR is able to revert the oxidative damage induced by CORT. In accordance with the neuroprotective role of the IGF-II/IGF-IIR reported in our study, pharmacotherapy approaches targeting this pathway may be useful for the treatment of diseases associated with cognitive deficits (i.e., neurodegenerative disorders, depression, etc.)., Graphical abstract fx1, Highlights • First evidence that IGF-II reverts oxidative synaptic damage produced by corticoids. • IGF-II recovers mitochondrial function in synapses after oxidative damage. • IGF-II restores mitochondrial distribution in neurons after oxidative damage. • Evidence of the involvement of IGF-II receptor in the recovery of synaptic function. • IGF-II reverts neurodegeneration induced by oxidative damage produced by corticoids.

Ladrón de Guevara-Miranda, David et al., Cocaine addiction disorder is notably aggravated by concomitant cognitive and emotional pathology that impedes recovery. We studied whether a persistent cognitive/emotional dysregulation in mice withdrawn from cocaine holds a neurobiological correlate within the hippocampus, a limbic region with a key role in anxiety andmemory but that has been scarcely investigated in cocaine addiction research. Mice were submitted to a chronic cocaine (20 mg/kg/day for 12 days) or vehicle treatment followed by 44 drug-free days. Some mice were then assessed on a battery of emotional (elevated plus-maze, light/dark box, open field, forced swimming) and cognitive (object and place recognition memory, cocaine-induced conditioned place preference, continuous spontaneous alternation) behavioral tests, while othermice remained in their home cage. Relevant hippocampal features [basal c-Fos activity, GABA+, parvalbumin (PV)+ and neuropeptide Y (NPY)+ interneurons and adult neurogenesis (cell proliferation and immature neurons)] were immunohistochemically assessed 73 days after the chronic cocaine or vehicle protocol. The cocaine-withdrawn mice showed no remarkable exploratory or emotional alterations but were consistently impaired in all the cognitive tasks. All the cocainewithdrawn groups, independent of whether they were submitted to behavioral assessment or not, showed enhanced basal c-Fos expression and an increased number of GABA+ cells in the dentate gyrus. Moreover, the cocaine-withdrawn mice previously submitted to behavioral training displayed a blunted experience-dependent regulation of PV+ and NPY+ neurons in the dentate gyrus, and neurogenesis in the hippocampus. Results highlight the importance of hippocampal neuroplasticity for the ingrained cognitive deficits present during chronic cocaine withdrawal., This research was funded by the Spanish Ministerio de Economía y Competitividad and the European Commission Regional Development Fund (UE-ERDF) (PSI2015- 73156-JIN to E.C-O, SAF12-36853 to M.A.-D and PSI2013-44901-P to L.J.S.), Junta de Andalucıa (CTS-2563 to M.A.-D) and Red de Trastornos Adictivos (RD12/ ́ 0028/0001 to F.R.F.). Authors received funds from the National System of Health Instituto de Salud Carlos III (Sara Borrell CD12/00455 to E.C-O; Miguel Servet CP14/00173 to A.S. and CP14/00212 to F.J.P.), from the Spanish Ministerio de Educación, Cultura y Deporte (FPU13/04819 to D.L.d.G.-M.) and from the University of Málaga (Plan Propio grant to C.M. and C.R.-V.).

Background: Anhedonia is a core feature of depressive disorders. The galanin N-terminal fragment (1-15) plays a role in mood regulation since it induces depression and anxiogenic-like effects in rats. In this study, we analysed galanin N-terminal fragment (1-15) actions in anhedonic-like behaviours in rats using operant and non-operant tests and the areas involved with these effects. Methods: Galanin N-terminal fragment (1-15) effects were analysed in saccharin self-administration, sucrose preference, novelty-suppressed feeding and female urine sniffing tests. The areas involved in galanin N-terminal fragment (1-15)-mediated effects were studied with positron emission tomography for in vivo imaging, and we analysed the ventral tegmental area and nucleus accumbens. Galanin N-terminal fragment (1-15) had effects on the mRNA expression of the dopamine transporters Dat and Vmat2; the C-Fos gene; the dopamine receptors D1, D2, D3, D5; and the galanin receptors 1 and 2. Results: Galanin N-terminal fragment (1-15) at a concentration of 3 nmol induced a strong anhedonia-like phenotype in all tests. The involvement of galanin receptor 2 was demonstrated with the galanin receptor 2 antagonist M871 (3 nmol). The 18F-fluorodeoxyglucose positron emission tomography images indicated the action of galanin N-terminal fragment (1-15) over several nuclei of the limbic system. Galanin N-terminal fragment (1-15)-mediated effects also involved changes in the expression of Dat, Vmat2, D3 and galanin receptors in the ventral tegmental area as well as the expression of C-Fos, D1, D2 and D3 and TH immunoreactivity in the nucleus accumbens. Conclusions: Our results indicated that galanin N-terminal fragment (1-15) exerts strong anhedonic-like effects and that this effect was accompanied by changes in the dopaminergic mesolimbic system. These results may provide a basis for the development of novel therapeutic strategies using galanin N-terminal fragment (1-15) analogues for the treatment of depression and reward-related diseases.

Galanin (1-15) [GAL(1–15)] participates in mood regulation and depression. GAL(1–15) is also able to enhance the antidepressant effects induced by Fluoxetine (FLX) in the forced swimming test through interaction between GALR1-GALR2 and 5-HT1A receptors that induced changes in the binding characteristics and mRNA of the 5-HT1AR in the hippocampus. Since the medial prefrontal cortex (mPFC) is a core region for the interaction between emotional processing and cognition with a high density of 5-HT1AR and GALR1 and GALR2, we have analyzed the binding characteristics and mRNA levels of 5-HT1AR in the mPFC after GAL(1–15)-FLX administration in the rats. GAL(1–15) increased the Kd and the Bmax of the 5HT1AR agonist binding in the mPFC as well as the mRNA levels of 5-HT1AR in mPFC. Moreover, GAL(1–15) reversed the effects of memory impairment induced by FLX(10 mg/kg) in the Novel Object Recognition task. GALR2 was involved in these effects, since the specific GALR2 antagonist M871 blocked GAL(1–15) mediated actions at behavioral level. On the contrary GAL(1–15) did not reverse the effect of FLX in the Object Location Memory task. In conclusion, our results describe an interactions between GAL(1–15) and FLX in the mPFC involving interactions at the 5-HT1AR receptor level in the plasma membrane with changes at the transcriptional level with implications also at functional level. The GALR1-GALR2-5-HT1A heteroreceptor could be postulated to be used to reverse some of the adverse effects of FLX on memory processes.

Galanin (GAL) and the NPYY1 agonist play a role in mood regulation and both neuropeptides interact in several central functions. The present study examined the interaction between Galanin receptor 2 (GALR2) and Neuropeptide Y Y1 receptor (NPYY1R) in the dentate gyrus (DG) of the Hippocampus in relation to depression-like behavior. Using receptor autoradiography, in situ hybridization and in situ proximity ligation assay an interaction between GALR and NPYY1R was demonstrated in the DG probably involving the formation of GALR2-NPYY1R heteroreceptor complexes. These complexes were specifically observed in the polymorphic and subgranular subregions of the DG, where both receptors were found to colocalize. Moreover, this GALR2/NPYY1R interaction was linked to an enhancement of the antidepressive-like behavior mediated by NPYY1R in the forced swimming test. Specific cells populations within DG subregions may be involved in this behavioral effect since the coactivation of GALR2 and NPYY1R enhances the NPYY1R-mediated reduction in the number of c-Fos immunoreactive nuclei in the polymorphic region. These results indicate that GALR2/NPYY1R interactions can provide a novel integrative mechanism in DG in depression-related behavior and may give the basis for the development of drugs targeting GALR2/NPYY1R heteroreceptor complexes in the DG of the hippocampus for the treatment of depression.

Alcohol consumption is considered a major risk factor for disease and mortality worldwide. In the absence of effective treatments in alcohol use disorders, it is important to find new biological targets that could modulate alcohol consumption. We tested the role of the N-terminal galanin fragment (1-15) [GAL(1-15)] in voluntary ethanol consumption in rats using the two-bottle choice paradigm as well as compare the effects of GAL(1-15) with the whole molecule of GAL. We describe for the first time that GAL(1-15), via central mechanisms, induces a strong reduction in preference and ethanol consumption in rats. These effects were significantly different than GAL. GAL receptor (GALR) 2 was involved in these effects, because the specific GALR2 antagonist M871 blocked GAL(1-15) mediated actions in preference and ethanol intake. Importantly, the mechanism of this action involves changes in GALR expression and also in immediate-early gene C-Fos and receptors-internalization-related gene Rab5 in the striatum. The relevance of the striatum as a target for GAL(1-15) was supported by the effect of GAL(1-15) on the locomotor activity of rats after ethanol administration. These results may give the basis for the development of novel therapeutics strategies using GAL(1-15) analogues for the treatment of alcohol use disorders in humans.

The introduction of allosteric receptor-receptor interactions in G protein-coupled receptor (GPCR) heteroreceptor complexes of the central nervous system (CNS) gave a new dimension to brain integration and neuropsychopharmacology. The molecular basis of learning and memory was proposed to be based on the reorganization of the homo- and heteroreceptor complexes in the postjunctional membrane of synapses. Long-term memory may be created by the transformation of parts of the heteroreceptor complexes into unique transcription factors which can lead to the formation of specific adapter proteins. The observation of the GPCR heterodimer network (GPCR-HetNet) indicated that the allosteric receptor-receptor interactions dramatically increase GPCR diversity and biased recognition and signaling leading to enhanced specificity in signaling. Dysfunction of the GPCR heteroreceptor complexes can lead to brain disease. The findings of serotonin (5-HT) hetero and isoreceptor complexes in the brain over the last decade give new targets for drug development in major depression. Neuromodulation of neuronal networks in depression via 5-HT, galanin peptides and zinc involve a number of GPCR heteroreceptor complexes in the raphe-hippocampal system: GalR1-5-HT1A, GalR1-5-HT1A-GPR39, GalR1-GalR2, and putative GalR1-GalR2-5-HT1A heteroreceptor complexes. The 5-HT1A receptor protomer remains a receptor enhancing antidepressant actions through its participation in hetero- and homoreceptor complexes listed above in balance with each other. In depression, neuromodulation of neuronal networks in the raphe-hippocampal system and the cortical regions via 5-HT and fibroblast growth factor 2 involves either FGFR1-5-HT1A heteroreceptor complexes or the 5-HT isoreceptor complexes such as 5-HT1A-5-HT7 and 5-HT1A-5-HT2A. Neuromodulation of neuronal networks in cocaine use disorder via dopamine (DA) and adenosine signals involve A2AR-D2R and A2AR-D2R-Sigma1R heteroreceptor complexes in the dorsal and ventral striatum. The excitatory modulation by A2AR agonists of the ventral striato-pallidal GABA anti-reward system via targeting the A2AR-D2R and A2AR-D2R-Sigma1R heteroreceptor complex holds high promise as a new way to treat cocaine use disorders. Neuromodulation of neuronal networks in schizophrenia via DA, adenosine, glutamate, 5-HT and neurotensin peptides and oxytocin, involving A2AR-D2R, D2R-NMDAR, A2AR-D2R-mGluR5, D2R-5-HT2A and D2R-oxytocinR heteroreceptor complexes opens up a new world of D2R protomer targets in the listed heterocomplexes for treatment of positive, negative and cognitive symptoms of schizophrenia.

Galanin is a 29 amino acid neuropeptide widely distributed in neurons within the central nervous system. Galanin exerts its biological activities through three different G protein-receptors and participates in a number of functions, including mood regulation. Not only Galanin but also Galanin N-terminal fragments like Galanin(1-15) are active at the central level. In this work, we review the latest findings in studies on Galanin and Galanin(1-15) in depression-related behaviours. Our focus is on animal models for depression, and we pay some attention to research data obtained in human studies. Since Serotonin (5-HT), especially through 5-HT1A, and Galanin receptors interact at both pre-and postsynaptic level, the development of drugs targeting potential GAL1-GAL2-5-HT1A heteroreceptor complexes linked to the raphe-hippocampal 5-HT neurons may represent new treatment strategies in depression.

Junta de Andalucia CVI6476.Universidad de Malaga. Campus de Excelencia Internacional Andalucia Tech.

Ponencia Invitada Galanin (GAL) is involved in several functions including mood regulation. The GAL N-terminal fragment (1-15) [GAL(1-15)] also participates at central level and a differential role of GAL(1-15) compared with GAL has been proposed. In this work we have analysed if GAL(1-15) contributes to depression- and anxiety -related behaviours using the forced swimming test, tail suspension test, open field and light/dark test. We tested the involvement of the GAL receptor 2 (GALR2) in GAL(1-15) effects with the GAL receptor antagonist M871 and with an in vivo model of siRNA GALR2 knockdown rats. The proximity of GALR1 and GALR1 was also examined with the proximity ligation assay (PLA). GAL(1-15) induced strong depression-like and anxiogenic-like effects in all the tests. The involvement of the GALR2 was demonstrated with M871 and with the siRNA GALR2 knockdown rats. The PLA indicated the existence of GALR1-GALR2 heteroreceptor complexes in the dorsal hippocampus and especially in the dorsal raphe nucleus. Our results indicate that GAL(1-15) exerts strong depression-related and anxiogenic-like effects and may give the basis for the development of drugs targeting GALR1-GALR2 heteroreceptor complexes in the raphe-limbic system for the treatment of depression and anxiety. This study was supported by Junta de Andalucía CVI6476. Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech.

The interactions between neuropeptide Y (NPY), specifically through NPY Y1 and Y2 receptor subtypes and the Galanin N-terminal fragment (1-15) [GAL(1-15)] were analyzed at the cardiovascular level. The cardiovascular effects of intracisternal coinjections of GAL(1-15) and NPY, NPY Y1 or Y2 agonist have been investigated as well as quantitative receptor autoradiography of the binding characteristics of NPY Y1 and Y2 receptor subtypes in the nucleus of the solitary tract (NTS) in the presence or absence of GAL(1-15). The coinjection of NPY with GAL(1-15) induces a significant vasopressor action. The coinjection of the NPY Y2 agonist and GAL(1-15) induced a similar increase of mean arterial pressure as induced by NPY+GAL(1-15), actions that were not observed with the NPY Y1 agonist+GAL(1-29). No interactions were observed at heart rate level. GAL(1-15) 3 nM significantly and substantially increased NPY-Y2 agonist binding in the NTS by about 50%. This effect was significantly blocked (p0.01) in the presence of the specific Galanin antagonist M40. The NPY-Y1 agonist binding was not modified in the presence of GAL(1-15). The present findings suggest the existence of a facilitatory effect of GAL(1-15) mediated via Galanin receptors on the NPY Y2 receptor subtype and its cardiovascular function within the NTS.

Due to the binding to a number of proteins to the receptor protomers in receptor heteromers in the brain, the term “heteroreceptor complexes” was introduced. A number of serotonin 5-HT1A heteroreceptor complexes were recently found to be linked to the ascending 5-HT pathways known to have a significant role in depression. The 5-HT1A–FGFR1 heteroreceptor complexes were involved in synergistically enhancing neuroplasticity in the hippocampus and in the dorsal raphe 5-HT nerve cells. The 5-HT1A protomer significantly increased FGFR1 protomer signaling in wild-type rats. Disturbances in the 5-HT1A–FGFR1 heteroreceptor complexes in the raphe-hippocampal 5-HT system were found in a genetic rat model of depression (Flinders sensitive line (FSL) rats). Deficits in FSL rats were observed in the ability of combined FGFR1 and 5-HT1A agonist cotreatment to produce antidepressant-like effects. It may in part reflect a failure of FGFR1 treatment to uncouple the 5-HT1A postjunctional receptors and autoreceptors from the hippocampal and dorsal raphe GIRK channels, respectively. This may result in maintained inhibition of hippocampal pyramidal nerve cell and dorsal raphe 5-HT nerve cell firing. Also, 5-HT1A–5-HT2A isoreceptor complexes were recently demonstrated to exist in the hippocampus and limbic cortex. They may play a role in depression through an ability of 5-HT2A protomer signaling to inhibit the 5-HT1A protomer recognition and signaling. Finally, galanin (1–15) was reported to enhance the antidepressant effects of fluoxetine through the putative formation of GalR1–GalR2–5-HT1A heteroreceptor complexes. Taken together, these novel 5-HT1A receptor complexes offer new targets for treatment of depression.

Galanin N-terminal fragment (1-15) [GAL(1-15)] is associated with depression-related and anxiogenic-like effects in rats. In this study, we analyzed the ability of GAL(1-15) to modulate 5-HT1A receptors (5-HT1AR), a key receptor in depression. GAL(1-15) enhanced the antidepressant effects induced by the 5-HT1AR agonist 8-OH-DPAT in the forced swimming test. These effects were stronger than the ones induced by Galanin (GAL). This action involved interactions at receptor level since GAL(1-15) affected the binding characteristics and the mRNA levels of 5-HT1AR in the dorsal hippocampus and dorsal raphe. The involvement of the GALR2 was demonstrated with the GALR2 antagonist M871. Proximity ligation assay experiments indicated that 5-HT1AR are in close proximity with GALR1 and GALR2 in both regions and in raphe RN33B cells. The current results indicate that GAL(1-15) enhances the antidepressant effects induced by 8-OH-DPAT acting on 5-HT1AR operating as postjunctional or as autoreceptors. These results may give the basis for the development of drugs targeting potential GALR1-GALR2-5-HT1AR heteroreceptor complexes linked to the raphe-hippocampal 5-HT neurons for the treatment of depression.

Background: Galanin (GAL) plays a role in mood regulation. In this study we analyzed the action of the active N-terminal fragment [GAL(1–15)] in anxiety- and depression-related behavioral tests in rats. Methods: The effect of GAL(1–15) was analyzed in the forced swimming test, tail suspension test, open field test, and light/dark test. The proximity of GAL1 and GAL2 receptors was examined with the proximity ligation assay (PLA). We tested the GAL receptors involved in GAL(1–15) effects with the GAL2 receptor antagonist M871 and with an in vivo model of siRNA GAL2 receptor knockdown or siRNA GAL1 receptor knockdown rats. The effects of GAL(1–15) were also studied in the cell line RN33B. Results: GAL(1–15) induced strong depression-like and anxiogenic-like effects in all the tests. These effects were stronger than the ones induced by GAL. The involvement of the GAL2 receptor was demonstrated with M871 and with the siRNA GAL2 receptor knockdown rats. The PLA indicated the possible existence of GAL1 and GAL2 heteroreceptor complexes in the dorsal hippocampus and especially in the dorsal raphe nucleus. In the siRNA GAL1 receptor knockdown rats the behavioral actions of GAL(1–15) disappeared, and in the siRNA GAL2 receptor knockdown rats the reductions of the behavioral actions of GAL(1–15) was linked to a disappearance of PLA. In the cell line RN33B, GAL(1–15) decreased 5-HT immunoreactivity more strongly than GAL. Conclusions: Our results indicate that GAL(1–15) exerts strong depression-related and anxiogenic-like effects and may give the basis for the development of drugs targeting GAL1 and GAL2 heteroreceptor complexes in the raphe-limbic system for the treatment of depression and anxiety.

Galanin N-terminal fragment (1-15) [Gal(1-15)] is involved in mood regulation. The intracerebroventricular (icv) administration of Gal(1-15) produces a depressive-like behaviour in the forced swim test (FST) and an anxiety-like behaviour in the open field test (OF) in rats. In this work we analyze the effect of Gal(1-15) in two more behavioural tests, the tail suspension test (TLT) and the light/dark test. Gal(1-15) (3nmol), effective dose in FST and OF, or artificial cerebrospinal were injected in animals (n=5-8) 15 minutes before the test. Behavioural assessment were conducted with at least one week between tests. Student’s t-test was used for comparision between experimental groups. In the light/dark test we analyzed during 5 min three parametres as indicators of anxiety-like behaviour. Gal(1-15) significantly reduced the time spent in the light compartiment by 52% (p

Comunicación Oral The Galanin N-terminal fragment (1-15) [GAL(1-15)] induces depressant- and anxiogenic- like actions. In this work, we have studied the role of GALR2 and GALR1 on the effects of GAL(1-15) in the Forced Swimming Test (FST) and Open Field Test (OFT) using siRNA GALR2 and GALR1 knockdown rats. Rats (n=6-14) were injected with GAL(1-15) 3nmol, GALR2 antagonist M871 3nmol in combination or alone 15 before the FST or OFT. The time of immobility, climbing and swimming were recorded during 5 min FST and Time and entries in the central square during 5min were scored in the OFT. In other experiment, rats (n=6-14) were injected Intracerebroventricular (icv) with siRNA-GALR2 or siRNA-GALR1 to generate the GALR knockdown rats. These knockdown rats were used in the OFT and in the FST after receiving icv GAL(1-15) 3nmol 15 min before the test. Vehicle was used as control. In the FST, M871 significantly blocked the increased immobility (p

The three cloned galanin receptors show a higher affinity for galanin than for galanin N-terminal fragments. Galanin fragment (1-15) binding sites were discovered in the rat Central Nervous System, especially in dorsal hippocampus, indicating a relevant role of galanin fragments in central galanin communication. The hypothesis was introduced that these N-terminal galanin fragment preferring sites are formed through the formation of GalR1-GalR2 heteromers which may play a significant role in mediating galanin fragment (1-15) signaling. In HEK293T cells evidence for the existence of GalR1-GalR2 heteroreceptor complexes were obtained with proximity ligation and BRET2 assays. PLA positive blobs representing GalR1-GalR2 heteroreceptor complexes were also observed in the raphe-hippocampal system. In CRE luciferase reporter gene assays, galanin (1-15) was more potent than galanin (1-29) in inhibiting the forskolin-induced increase of luciferase activity in GalR1-GalR2 transfected cells. The inhibition of CREB by 50 nM of galanin (1-15) and of galanin (1-29) was fully counteracted by the non-selective galanin antagonist M35 and the selective GalR2 antagonist M871. These results suggested that the orthosteric agonist binding site of GalR1 protomer may have an increased affinity for the galanin (115) vs galanin (1-29) which can lead to its demonstrated increase in potency to inhibit CREB vs galanin (1-29). In contrast, in NFAT reporter gene assays galanin (1-29) shows a higher efficacy than galanin (115) in increasing Gq/11 mediated signaling over the GalR2 of these heteroreceptor complexes. This disbalance in the signaling of the GalR1-GalR2 heteroreceptor complexes induced by galanin (1-15) may contribute to depression-like actions since GalR1 agonists produce such effects. (C) 2014 Elsevier Inc. All rights reserved.

Galanin (GAL) and neuropeptide Y (NPY) are neuropeptides involved in behaviors associated with anxiety. Both neuropeptides interact in several central functions. However, the potential behavioral and cellular interactions between them in anxiety are unknown. GAL was found to act through GAL receptor 2 (GALR2) to enhance NPYY1 receptor (NPYY1R)-mediated anxiolytic behaviors in rats. Using receptor autoradiography, c-Fos expression and in situ proximity ligation assay, the medial paracapsular intercalated nuclei of the amygdala were determined to be a key area in the interaction probably involving the formation of GALR2/NPYY1R heteroreceptor complexes. In cell cultures costimulation of GALR2 and NPYY1R induced changes in the functions of these receptors. The changes involved a potentiation of the decrease in the phosphorylation of CREB induced by NPYY1R and a delay in the internalization of NPYY1R. These results indicate that GALR2/NPYY1R interactions can provide a novel integrative amygdaloid mechanism in anxiety.

Galanin receptor (GalR) subtypes1-3 linked to central galanin neurons may form heteromers with each other and other types of G protein coupled receptors (GPCRs) in the Central Nervous System (CNS). These heteromers may be one molecular mechanism for galanin peptides and their N-terminal fragments (gal 1-15) to modulate the function of different types of glia-neuronal networks in the CNS, especially the emotional and the cardiovascular networks. GalR-5-HT1A heteromers likely exist with antagonistic GalR-5-HT1A receptor-receptor interactions in the ascending midbrain raphe 5-HT neuron systems and their target regions. They represent a novel target for antidepressant drugs. Evidence is given for the existence of GalR1-5-HT1A heteromers in cellular models with transinhibition of the protomer signaling. A GalR1-GalR2 heteromer is proposed to be a galanin N-terminal fragment preferring receptor (1-15) in the CNS. Furthermore, a GalR1-GalR2-5-HT1A heterotrimer is postulated to explain why only galanin (1-15) but not galanin (1-29) can antagonistically modulate the 5-HT1A receptors in the dorsal hippocampus rich in gal fragment binding sites. The results underline a putative role of different types of GalR-5-HT1A heteroreceptor complexes in depression. GalR antagonists may also have therapeutic actions in depression by blocking the antagonistic GalR-NPYY1 receptor interactions in putative GalR-NPYY1 receptor heteromers in the CNS resulting in increases in NPYY1 transmission and antidepressant effects. In contrast the galanin fragment receptor (a postulated GalR1-GalR2 heteromer) appears to be linked to the NPYY2 receptor enhancing the affinity of the NPYY2 binding sites in a putative GalR1-GalR2-NPYY2 heterotrimer. Finally, putative GalR-α2-adrenoreceptor heteromers with antagonistic receptor-receptor interactions may be a widespread mechanism in the CNS for integration of galanin and noradrenaline signals also of likely relevance for depression.

Galanin (GAL) is a peptide involved in multiple functions, including central cardiovascular control. In this review, the role of GAL and its fragments in the modulation of cardiovascular neuronal networks in the nucleus of the solitary tract is presented, including its interaction with the classical neurotransmitters and other neuropeptides involved in cardiovascular responses in this nucleus. First, we describe the cardiovascular responses of GAL and the pathway involved in these responses. Then we summarize findings obtained in our laboratory on how GAL, through its receptors, interacts with two other neuropeptides--Neuropeptide Y and Angiotensin II and their receptors--as they have particularly conspicuous cardiovascular effects. All these results strengthen the role of GAL in central cardiovascular control and indicate the existence of interactions among GAL receptor subtypes and alpha2-adrenergic receptors, AT1, and Y1 receptor subtypes. These interactions are crucial for understanding the integrative mechanisms responsible for the organization of the cardiovascular responses from the NTS.

Galanin (GAL) is a peptide involved in multiple functions, including central cardiovascular control. In this review, the role of GAL and its fragments in the modulation of cardiovascular neuronal networks in the nucleus of the solitary tract is presented, including its interaction with the classical neurotransmitters and other neuropeptides involved in cardiovascular responses in this nucleus. First, we describe the cardiovascular responses of GAL and the pathway involved in these responses. Then we summarize findings obtained in our laboratory on how GAL, through its receptors, interacts with two other neuropeptides – Neuropeptide Y and Angiotensin II and their receptors – as they have particularly conspicuous cardiovascular effects. All these results strengthen the role of GAL in central cardiovascular control and indicate the existence of interactions among GAL receptor subtypes and α2-adrenergic receptors, AT1, and Y1 receptor subtypes. These interactions are crucial for understanding the integrative mechanisms responsible for the organization of the cardiovascular responses from the NTS.

The aim of this study was to evaluate by quantitative receptor autoradiography the interactions between Neuropeptide Y Y1 (NPY Y1) and Galanin (GAL) receptors in the dorsal raphe nucleus (DRN) where both GAL receptors and NPY Y1 receptors exist. The ability of the GAL receptor antagonist M35 to block the GAL action was also evaluated. Double immunocytochemical staining of 5-hydroxytryptmine and c-Fos and stereology techniques were used to study the specific cell activation in the DRN after the intracerebroventricular coinjections of GAL and the NPY Y1/Y5 agonist [ 125 I] Leu 31 ,Pro 34 PYY. GAL (0.3 nM) decreases [ 125 I] Leu 31 ,Pro 34 PYY binding in the DRN by 48% (p < 0.01) as shown by quantitative receptor autoradiography. This effect was reversed with the GAL receptor antagonist M35. Intracerebroventricular coinjections of NPY Y1/Y5 agonist and GAL reduced the c-Fos expression in the serotoninergic cells induced by the NPY Y1/Y5 agonist in DRN. These results indicate the existence of antagonistic interactions between GAL receptors and NPY Y1 receptors in the DRN that may be of relevance in mood disorders.

groups. GAL and Y1 agonist alone did not change any of the parameters analyzed. However in the open field test the coadministration of GAL and Y1 agonist significantly increased the number of entries (p