Publicação
Social memory in zebrafish : behavioral assessment and the role of brain-derived neurotrophic factor (BDNF)
| Resumo: | The ability of animals to gather information about their social and physical environment is essential for their ecological function. Animals are often organize conspecifics into categories (e.g. sex, age, hierarchical status). This social organization is underpinned by social recognition. Individuals use an assortment of different cues to obtain information about their environment and to recognize the individuals that they encounter. The present study evaluated the influence of 3 different sensory cues on social recognition: visual-only; olfactory-only and visual + olfactory. We used two different paradigms to assess social recognition memory – social discrimination paradigm and a habituation-dishabituation paradigm – both adapted from mouse studies. We also explored an asocial task – novel object test. A series of six experiments were performed by each individual. Subsequently, bdnf expression levels were evaluated in hippocampus and amygdala. The behavioral results show that zebrafish: i) did not demonstrate preference for any of the objects presented 24h after the initial test; ii) preferentially associated with conspecifics that are novel, when using both chemical and visual cues; iii) exhibit preference for familiar conspecifics when only visually cues are accessible; iv) did not show preference between two individuals, when only chemical cues were available; v) failed to demonstrate social recognition memory using the habituation-dishabituation paradigm; vi) are highly inquisitive animals. The genetic expression analysis demonstrates no differences in bdnf expression levels in the amygdala. However, in the hippocampus, low-levels of bdnf were present when animals performed a discrimination paradigm based only on olfactory cues; in contrast with individuals that performed the same behavioral paradigm based on visual and visual + chemical cues. ). Here we propose that the high levels of BDNF observed in the Dl could affect LTP and consequently the production and secretion of OT in the Dm. Our findings present a new possibility for the role of neural connections between the Dl and Dm regions, mediated by BDNF, with significant impact on social memory. We also evaluated the use of immediate early genes (c-fos and bdnf) as neural response markers in the zebrafish telencephalon. We analyzed animals that were submitted to a kainic acid treatment. To study the temporal response of IEG’s (c-fos and bdnf) to the treatment, an analysis of gene expression (qPCR) and protein levels (Western-blot) was performed. Animals were given intraperitoneal injections (0.5mg/Kg) of saline solution (control group) or kainic acid (treatment group) and sacrificed at different sampling time points (immediately after, 0min., 30min., 1h, 2h, 4h, 8h, 24h and 48h). The results show that c-fos suffered an up-regulation 30 min. after treatment; followed by an abrupt decrease in c-fos expression levels. However, protein levels did not show significant differences in C-FOS protein. Regarding bdnf: an up-regulation was observed 0min. after saline solution administration; 48h after administration of either KA or saline solution, a decrease in bdnf expression levels was observed. At the protein level both pro-BDNF and mature-BDNF levels were analyzed. Pro-BDNF levels increase 2h and 8h after saline solution administration; and 0min., 1h, 4h, 24h and 48h after KA administration. In contrast, mature-BDNF levels increase 0min. and 30min. after saline solution administration; and 0min., 1h, 2h, 4h, 8h, 24h and 48h after KA administration. The present work demonstrates the usefulness of zebrafish in studying social memory, by the validation of paradigms to that effect. This work also suggests that the hippocampus possesses a role in this type of memory, depending on the origin of the cues employed. |
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| Autores principais: | Madeira, Natália da Costa, 1990- |
| Assunto: | Memória Peixe-zebra Fator neurotrófico derivado do cérebro (BDNF) Hipocampo Teses de mestrado - 2015 |
| Ano: | 2015 |
| País: | Portugal |
| Tipo de documento: | dissertação de mestrado |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Universidade de Lisboa |
| Idioma: | inglês |
| Origem: | Repositório da Universidade de Lisboa |
| Resumo: | The ability of animals to gather information about their social and physical environment is essential for their ecological function. Animals are often organize conspecifics into categories (e.g. sex, age, hierarchical status). This social organization is underpinned by social recognition. Individuals use an assortment of different cues to obtain information about their environment and to recognize the individuals that they encounter. The present study evaluated the influence of 3 different sensory cues on social recognition: visual-only; olfactory-only and visual + olfactory. We used two different paradigms to assess social recognition memory – social discrimination paradigm and a habituation-dishabituation paradigm – both adapted from mouse studies. We also explored an asocial task – novel object test. A series of six experiments were performed by each individual. Subsequently, bdnf expression levels were evaluated in hippocampus and amygdala. The behavioral results show that zebrafish: i) did not demonstrate preference for any of the objects presented 24h after the initial test; ii) preferentially associated with conspecifics that are novel, when using both chemical and visual cues; iii) exhibit preference for familiar conspecifics when only visually cues are accessible; iv) did not show preference between two individuals, when only chemical cues were available; v) failed to demonstrate social recognition memory using the habituation-dishabituation paradigm; vi) are highly inquisitive animals. The genetic expression analysis demonstrates no differences in bdnf expression levels in the amygdala. However, in the hippocampus, low-levels of bdnf were present when animals performed a discrimination paradigm based only on olfactory cues; in contrast with individuals that performed the same behavioral paradigm based on visual and visual + chemical cues. ). Here we propose that the high levels of BDNF observed in the Dl could affect LTP and consequently the production and secretion of OT in the Dm. Our findings present a new possibility for the role of neural connections between the Dl and Dm regions, mediated by BDNF, with significant impact on social memory. We also evaluated the use of immediate early genes (c-fos and bdnf) as neural response markers in the zebrafish telencephalon. We analyzed animals that were submitted to a kainic acid treatment. To study the temporal response of IEG’s (c-fos and bdnf) to the treatment, an analysis of gene expression (qPCR) and protein levels (Western-blot) was performed. Animals were given intraperitoneal injections (0.5mg/Kg) of saline solution (control group) or kainic acid (treatment group) and sacrificed at different sampling time points (immediately after, 0min., 30min., 1h, 2h, 4h, 8h, 24h and 48h). The results show that c-fos suffered an up-regulation 30 min. after treatment; followed by an abrupt decrease in c-fos expression levels. However, protein levels did not show significant differences in C-FOS protein. Regarding bdnf: an up-regulation was observed 0min. after saline solution administration; 48h after administration of either KA or saline solution, a decrease in bdnf expression levels was observed. At the protein level both pro-BDNF and mature-BDNF levels were analyzed. Pro-BDNF levels increase 2h and 8h after saline solution administration; and 0min., 1h, 4h, 24h and 48h after KA administration. In contrast, mature-BDNF levels increase 0min. and 30min. after saline solution administration; and 0min., 1h, 2h, 4h, 8h, 24h and 48h after KA administration. The present work demonstrates the usefulness of zebrafish in studying social memory, by the validation of paradigms to that effect. This work also suggests that the hippocampus possesses a role in this type of memory, depending on the origin of the cues employed. |
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