Effects of galanin n-terminal fragment (1-15) in the light/dark and tail suspension tests

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<0.05) and the latency time for entering the dark box by 65% (p<0.05). An increased in the latency time for re-entering the light box was also observed (p<0.05). In the TST, total immobility time was analyzed during 6 min test as parameter indicator of depressive-like behaviour. Gal(1-15) significantly increased rat immobility by 16% (p<0.05). Our results describe that Gal(1-15) exerts strong depressive- and anxiety-like effects in these tests, indicating a potential role of Gal(1-15) in mood disorders. These results may give the basis for the development of novel therapeutic drugs targeting Gal(1-15) for depression and anxiety.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. Junta de Andalucia CVI6476 // Spanish Ministry of Economy and Competitiveness (PSI2013-44901-P to L.J.S). Author A.F-B. holds a ‘FPI’ grant from the Spanish Ministry of Economy and Competitiviness (grant number: BES-2014-068426)

Galanin n-terminal fragment (1-15) induces an anxiety- and depressive-like behaviours in the light/dark and tail suspension tests

Galanin N-terminal fragment (1-15) [Gal(1-15)] is involved in mood regulation. We have shown that 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. In light/dark test we studied during 5 min the latency time for entering the dark box, time spent in the light compartiment, and the latency time for re-entering the light box as parameters indicators of anxiety-like behaviour. In TLT total immobility time was analyzed during 6 min test as parameter indicator of depressive-like behaviour. Groups of rats (n=5-8) were injected icv with Gal(1-15) 3nmol, a dose effective in FST and OF, or artificial cerebrospinal fluid 15 minutes before the test. Behavioural assessment were conducted with at least one week between tests. Student’s t-test was used for comparation between experimental groups. In the light/dark test Gal(1-15) 3nmol significantly reduced the time spent in the light compartiment by 52% (p<0.05) and the latency time for entering the dark box by 65% (p<0.05). An increased in the latency time for re-entering the light box was also observed (p<0.05). This pattern of results reflects an anxiogenic-like effects of Gal(1-15) in this test. In the TST, the administration of Gal(1-15) 3nmol significantly increased rat immobility by 16% (p<0.05) indicating a depressive-like effect. These results confirm the depressive- and anxiety-like effects of Gal(1-15) in rats. Future therapeutic strategies based on these results could be developed for depression and anxiety disorders. This work has been supported by the Junta de Andalucia CVI6476 and Spanish Ministry of Economy and Competitiveness (PSI2013-44901-P to L.J.S)Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. This work has been supported by the Junta de Andalucia CVI6476 and Spanish Ministry of Economy and Competitiveness (PSI2013-44901-P to L.J.S)Author A.F-B. holds a ‘FPI’ grant from the Spanish Ministry of Economy and Competitiviness (grant number BES-2014-068426)

Role of the 5-HT1A receptors in the effect of Galanin(1-15) on Fluoxetine-mediated action in the forced swimming test

Galanin N-terminal fragment (1-15) [GAL(1-15)] modulates the antidepressant effects induced by the 5-HT1A receptor (5-HT1AR) agonist in the forced swimming test (FST) and the binding characteristics and mRNA levels of 5-HT1AR in the dorsal hippocampus and dorsal raphe (DR). Recently, we observed that GAL(1-15) enhanced the antidepressant-like effects induced by Fluoxetine (FLX) in the FST. In this work, we have studied whether the effects of GAL(1–15) on FLX action were mediated via 5-HT1AR, analyzing the effect of the 5-HT1AR antagonist WAY100635 in this effect and if the binding characteristics and mRNA levels of 5-HT1AR in the DR and dorsal hippocampus are modified by GAL(1-15)+FLX. Groups of rats (n=6-8) received three injections of sc FLX(10mg/kg) and 15 minutes before the FST a single icv injection of GAL(1-15) (1nmol) and 5HT1AR antagonist WAY100635(6nmol) icv alone or in combination. We also analyzed the effects of GAL(1-15)+FLX in the binding characteristics of the 5-HT1AR agonist [H3]-8-OH-DPAT and 5-HT1A mRNA levels in the DR, CA1 and Dentate Gyrus (DG). WAY100635 significantly blocked the reduction in immobility time (p<0.05), and the increase in swimming time (p<0.01) induced by GAL(1-15)+FLX in the FST. GAL(1-15)+FLX produced a significant increase in the 5HT1AR mRNA levels in CA1 (p<0.05) and DG (p<0.05). This effect was not observed in the DR. Moreover, GAL(1-15)+FLX produced a significant decrease in the Kd value (p<0.01) and in the Bmax value (p<0.05) of [3H]-8-OH-DPAT in the DG. These effects were not observed in the CA1 or in the DR. These results indicate that 5HT1AR participates in the GAL(1-15)/FLX interactions in the FST and the mechanism underlying affected the binding characteristics and the mRNA levels of 5-HT1AR specifically in the dorsal hippocampus. The heteroreceptor 5-HT1AR-GALR1-GALR2 located in the dorsal hippocampus may be the target for GAL(1-15). This work was supported by SAF2016-79008-P; PSI2013-44901-P.SAF2016-79008-P; PSI2013-44901-P. Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

A Role For Galanin N-Terminal Fragment (1-15) In Anxiety And Depression in rats

Ponencia InvitadaGalanin (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

Galanin decreases NPYY1R internalization and β- Arrestin2 recruitment

We have recently described a Galanin receptor 2(GALR2) and Neuropeptide Y Y1 receptor(NPYY1R) interaction at behavioural, cellular and receptor levels through GALR2/NPYY1R heterodimers. The aim of this work was to study if GALR2 and NPYY1R costimulation modified NPYY1R internalization and β-Arrestin recruitment after in HEK293T cells. HEK293T cells were transfected with NPYY1REGFPor β-Arrestin2GFP2 cloned with standard molecular biology techniques employing PCR and fragment replacement strategies. NPYY1REGFP/GALR2 and NPYY1R/GALR2 with β- Arrestin2GFP2 HEK293T coexpressing cells were incubated with NPY 1μM and/or GAL1μM, at different times. Antagonist studies were performed 15 min prior to the addition of agonist with NPYY1R antagonist BIBP3226 10μM or GALR2 antagonist M871 10 μM. Timed-interval images of NPYY1REGFP or β-Arrestin2GFP2 endosomes in different cell groups were acquired using a confocal microscope following agonist addition. Percentage of internalization was determined by Leica software analysis of total membrane fluorescence compared to total internal compartment fluorescence at the various time points. We observed that addition of NPY induced a rapid decrease in the cell surface expression of NPYY1REGFP and a redistribution of β-Arrestin2GFP2. In fact, we observed a maximum of internalization of 80% three minutes after the NPY stimulation. However, combined treatment with GAL and NPY induced a delay in the internalization of NPYY1REGFP, with a maximum of internalization thirty minutes after the co-stimulation. Moreover, a delay in the β-Arrestin2GFP2 redistribution was observed. The specific GALR2 antagonist M871 abolished these delays in internalization of NPYY1REGFP and β-Arrestin2GFP2 redistribution, suggesting that this effect was mediated through the coactivation of GALR2 and NPYY1R. These results demonstrate that costimulation with GAL and NPY delays the internalization of  NPYY1REGFP by decreasing recruitment of β-Arrestin2GFP2 and probably could change intracellular signaling. This study was supported by Junta de Andalucia CVI6476.Junta de Andalucia CVI6476.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Galanin receptor 2 modifies neuropeptide Y Y1 receptor internalization and β-Arrestin recruitment

We have recently described a Galanin receptor 2(GALR2) and Neuropeptide Y Y1 receptor(NPYY1R) interaction at behavioural, cellular and receptor levels through GALR2/NPYY1R heterodimers. The aim of this work was to study if GALR2 and NPYY1R costimulation modified NPYY1R internalization and β-Arrestin recruitment after in HEK293T cells. HEK293T cells were transfected with NPYY1REGFPor β-Arrestin2GFP2 cloned with standard molecular biology techniques employing PCR and fragment replacement strategies. NPYY1REGFP/GALR2 and NPYY1R/GALR2 with β- Arrestin2GFP2 HEK293T coexpressing cells were incubated with NPY 1μM and/or GAL1μM, at different times. Antagonist studies were performed 15 min prior to the addition of agonist with NPYY1R antagonist BIBP3226 10μM or GALR2 antagonist M871 10 μM. Timed-interval images of NPYY1REGFP or β-Arrestin2GFP2 endosomes in different cell groups were acquired using a confocal microscope following agonist addition. Percentage of internalization was determined by Leica software analysis of total membrane fluorescence compared to total internal compartment fluorescence at the various time points. We observed that addition of NPY induced a rapid decrease in the cell surface expression of NPYY1REGFP and a redistribution of β-Arrestin2GFP2. In fact, we observed a maximum of internalization of 80% three minutes after the NPY stimulation. However, combined treatment with GAL and NPY induced a delay in the internalization of NPYY1REGFP, with a maximum of internalization thirty minutes after the co-stimulation. Moreover, a delay in the β-Arrestin2GFP2 redistribution was observed. The specific GALR2 antagonist M871 abolished these delays in internalization of NPYY1REGFP and β-Arrestin2GFP2 redistribution, suggesting that this effect was mediated through the coactivation of GALR2 and NPYY1R. These results demonstrate that costimulation with GAL and NPY delays the internalization of  NPYY1REGFP by decreasing recruitment of β-Arrestin2GFP2 and probably could change intracellular signaling. This study was supported by Junta de Andalucia CVI6476.Junta de Andalucia CVI6476.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Galanin interacts with Neuropeptide Y Y1 receptor in the dentate gyrus of the hippocampus through GALR2/NPYY1R heterodimers

We have shown Galanin(GAL) and Neuropeptide Y Y1(NPYY1) interactions at behavioural, cellular and receptor levels through GALR2/NPYY1R heterodimers in the amygdala. The aim of this work was to analyze GAL/NPYY1R interactions in the Dentate Gyrus(DG) of the Hippocampus, using autoradiographic, in situ hybridization and in situ proximity ligation assay(PLA). Rats(n=6) were sacrificed 15 minutes or 5 hours after icv injections of GAL(3nmol) and DG sections were incubated with NPYY1R agonist [I125]-[Leu31,Pro34]PYY(25 pM) or NPYY1R-33PdATP specific probe, for autoradiography and in situ hybridization respectively. Autoradiograms were analyzed using NIH image analysis system and Student’s unpaired t-test was used. For PLA, DG sections were incubated with anti-GALR2 Rabbit(1:100) and anti-NPYY1R Goat(1:200). PLA signals were detected with PLA PLUS or MINUS probes for rabbit or goat/mouse antibodies. PLA signals were visualized by using a confocal microscope Leica TCS-SL confocal microscope(Leica). We observed that GAL significant increased the NPYY1R agonist [I125]-[Leu31,Pro34]PYY binding in the DG by 20% (p<0,05) and the NPYY1R mRNA expression in the granular layer of DG by 31% (p<0,001). Moreover, PLA-positive red clusters were found specifically in the polymorphic layer and subgranular zone of the DG. No PLA clusters were observed neither in the molecular layer of the DG nor in the corpus callosum, an area that seems to lack of GALR2 receptor. These results demonstrate a novel mechanism of interaction between GAL and NPY1R in the DG at receptor level, probably involving the formation of GALR2/NPYY1R heteroreceptor complexes. Study supported by Junta de Andalucia CVI6476.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Antidepressant-like effects induced by galanin 2/neuropeptide Y Y1 heterodimers in the dentate gyrus of the hippocampus

Previously, we have described the Galanin (GAL) and Neuropeptide Y Y1 (NPYY1) interactions through GAL receptor 2 and NPYY1 receptor 1 (GALR2/NPYY1R) heterodimers in the Dentate Gyrus (DG) of the Hippocampus, using autoradiographic, in situ hybridization and in situ proximity ligation assay(PLA) (1,2). The current work is to evaluate GALR2 and NPYY1R interactions in relation to depression-like behaviour and c-Fos expression in the Hippocampal DG. Rats (n=6-8) were forced to swim for a 15-min period (pre-test) and 24 h later were subjected to a 5-min swimming session (test) 15 min after the administration alone or in combination of GAL, the NPYY1R agonist [Leu31,Pro34]NPY and the GALR2 antagonist M871. The total duration of immobility, swimming, and climbing periods were scored during the test. For c-Fos immunohistochemistry, experimental groups of rats were anesthetized with sodium pentobarbital (100 mg/kg, i.p.) and perfused with 4 % Paraformaldehyde 90 min after icv injections. Then, brains were coronally sliced and immunostained. As primary antibodies, an antibody against c-Fos protein (1:5000, sc- 52, Santa Cruz Biotechnology, CA, USA), revealed with 3,3´-Diaminobenzidine (DAB) plus nickel, was used as an indirect marker of neural activity. The antibody to Calbindin-D28 k (1:1000, Santa Cruz Biotecnology, CA, USA), revealed with DAB, was used to outline the granular region since it marks mainly hippocampal granule cells. Sections were analyzed using the optical fractionator stereological method. We observed that icv injection of GAL and NPYY1R agonist significantly enhanced the decrease in the immobility (p<0,001) and the increase in the swimming behaviour (p<0,001) compared with the NPYY1R agonist alone. Moreover, a significant enhancement of the decrease in climbing behavior (p<0.05) was also observed. Furthermore, GALR2 is involved in this GALR/NPYY1R interaction, since the presence of the GALR2 antagonist M871 counteracted the enhancement of the decrease in immobility (p<0.01) and in climbing behavior (p<0.05) as well as the increase in swimming time (p<0.001) induced by the coadministration of GAL and NPYY1R agonist in the FST. Specific cells populations within DG subregions may be involved in this behavioural effect since the coadministration of GAL and NPYY1 agonist enhances the NPYY1R-mediated reduction (p<0.05) in the number of c-Fos immunoreactive nuclei in the polymorphic region. In this region, the GABA interneurons could be involved in the interaction since c-Fos IR colocalized with a GABAergic marker (GAD65/67) after NPYY1R agonist injection. Moreover, within the granular cells layer, GAL and NPYY1 agonist coadministration significantly increased c-Fos IR expression in the entire granular cell layer compared with GAL (p<0.05) and [Leu31,Pro34]NPY (p<0.01) alone. Again, the co-treatment with the GALR2 antagonist M871 completely reversed the GAL contribution to the responses in both regions, the polymorphic and the granular layer of the DG, demonstrating the involvement of GALR2 in the GAL actions. 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. Study supported by Junta de Andalucia CVI6476 and Proyecto Puente-Universidad de Málaga. 1. Galanin receptor 2-neuropeptide Y Y1 receptor interactions in the dentate gyrus are related with antidepressant-like effects. Narváez M, Borroto-Escuela DO, Millón C, Gago B, Flores-Burgess A, Santín L, Fuxe K, Narváez JA, Díaz-Cabiale Z. Brain Struct Funct 2016 Nov. 221(8):4129-4139. 2. Galanin receptor 2-neuropeptide Y Y1 receptor interactions in the amygdala lead to increased anxiolytic actions. Narváez M, Millón C, Borroto-Escuela D, Flores-Burgess A, Santín L, Parrado C, Gago B, Puigcerver A, Fuxe K, Narváez JA, Díaz-Cabiale Z. Brain Struct Funct. 2015 Jul;220(4):2289-301.Study supported by Junta de Andalucia CVI6476 and Proyecto Puente. Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

GALR2/NPYY1R heterodimers interact at receptor level in the dentate gyrus of the hippocampus in rats

Previously, we have described Galanin(GAL) and Neuropeptide Y Y1(NPYY1) interactions at behavioural, cellular and receptor levels through GALR2/NPYY1R heterodimers in the amygdala. The aim of this work was to study GAL/NPYY1R interactions in the Dentate Gyrus (DG) of the Hippocampus, using autoradiographic, in situ hybridization and in situ proximity ligation assay (PLA). Rats (n=6) were sacrificed 15 minutes or 5 hours after icv injections of GAL (3nmol) and DG sections were incubated with NPYY1R agonist [I125]-[Leu31,Pro34]PYY (25 pM) or NPYY1R-33PdATP specific probe, for autoradiography and in situ hybridization respectively. Autoradiograms were analyzed using NIH image analysis system and Student’s unpaired t-test was used. For PLA, DG sections were incubated with anti-GALR2 Rabbit (1:100) and anti-NPYY1R Goat (1:200). PLA signals were detected with PLA PLUS or MINUS probes for rabbit or goat/mouse antibodies. PLA signals were visualized by using a confocal microscope Leica TCS-SL confocal microscope (Leica). We observed that GAL significant increased the NPYY1R agonist [I125]-[Leu31,Pro34]PYY binding in the DG by 20% (p<0,05) and the NPYY1R mRNA expression in the granular layer of DG by 31% (p<0,001). Moreover, PLA-positive red clusters were found specifically in the polymorphic layer and subgranular zone of the DG. No PLA clusters were observed neither in the molecular layer of the DG nor in the corpus callosum, an area that seems to lack of GALR2 receptor. These results demonstrate a novel mechanism of interaction between GAL and NPY1R in the DG at receptor level, probably involving the formation of GALR2/NPYY1R heteroreceptor complexes. Study supported by Junta de Andalucia CVI6476.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. Study supported by Junta de Andalucia CVI6476

GAL(1-15) induces a depression and anxiogenic effect trough GALR1/GALR2 heteroreceptor: siRNA GALR1/GALR2 knockdown rats

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<0.001) and decreased climbing (p<0.01) induced by GAL(1-15). In the OFT M871 also significantly decreased the number of entries (p<0.001) and time spent in the center (p<0.05) mediated by GAL(1-15). Down-regulation of GALR2 or GALR1 by siRNA was sufficient to block the effect of GAL(1-15) in behavioural tests. Thus, GAL(1-15) 3nmol lacked effect on the immobility, climbing and swimming time in the FST. The same effect was observed in the number of entries and time spent in the central square in the OFT. These results indicated that GALR1 and GALR2 are involved in the GAL(1-15) depression- and anxiogenic-like effects suggesting that GAL(1-15) could act through GALR1/GALR2 heteroreceptor complex. These findings may give the basis for the development of novel therapeutic drugs targeting GAL(1-15) system for treatment of depression and anxiety disorders. This study was supported by Junta de Andalucía CVI6476.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech