Publicação
Neural regulation of fly’s cardiac activity during defensive behaviours
| Resumo: | Abstract The ability to perceive and respond to threatening situations is vital for animal survival. Defensive behaviours, including fighting, fleeing, and freezing, are employed across taxonomic groups and can vary based on the characteristics of the threat stimulus and the animal's internal state. Previous research has indicated that defensive responses in animals, including fruit flies, are often accompanied by distinct changes in cardiac activity. Flight-or-flee behaviours have been associated with increased cardiac activity while freezing response is characterized by a decreased cardiac activity. The evolutionary convergence of cardiac changes suggests an underlying physiological mechanism that contributes to behavioural responses to threats. However, the specific role of cardiac activity in shaping defensive behaviours and the molecular pathways involved remain poorly understood. In this study, we focus on loom-triggered defensive behaviours and the cardiac changes associated with them in Drosophila melanogaster. We investigate the role of the cardioacceleratory neuropeptide CCAP (crustacean cardioactive peptide) in modulating cardiac activity and its impact on behaviour during threat perception. Using the GAL/UAS system and RNA interference methodology, we aimed to impair the expression of the CCAP receptor (CCAPR) specifically in cardiomyocytes of Drosophila melanogaster. We analysed the behaviour of tethered flies walking on a ball before and after inescapable threat stimulation (looming stimulus), thus evaluating the effect of CCAPR knockdown on basal cardiac activity and during threat stimulation. Our findings reveal that CCAP signalling plays a significant role in regulating the two main features of Drosophila cardiac activity during baseline. We find that flies expressing the CCAPR RNAi (CCAPR RNAi flies) show slower and more variable heart rate (heart beating rate) and faster cardiac reversal rate (the rate of alternation between beating in the backward and forward direction) than control flies. Upon stimulation, two states of freezing were observed (quiescent and twitching freezing) and were accompanied by different cardiac dynamics. Intriguingly, flies with CCAPR RNAi showed reduced sustainability of the bradycardia during freezing, aligned to a disruption in the sustainability of quiescent freezing behaviour. This hypothesis would agree with unpublished data from the lab that shows that freely walking CCAPR RNAi flies present reduced freezing response. Though a leaky expression of the tinGal4 driver in the Nervous System might underly the reduced freezing sustainability, this research contributes to understanding the interplay between physiological and behavioural responses to threats, shedding light on evolutionary and adaptive mechanisms underlying defensive behaviours in Drosophila melanogaster. |
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| Autores principais: | Manuel, Cleusia Varinia Lourenço |
| Assunto: | CCAP Heart Rate Cardiac Reversal Freezing States Looming Stimulus RNA Interference |
| Ano: | 2024 |
| País: | Portugal |
| Tipo de documento: | dissertação de mestrado |
| Tipo de acesso: | acesso embargado |
| Instituição associada: | Universidade Nova de Lisboa |
| Idioma: | inglês |
| Origem: | Repositório Institucional da UNL |
| Resumo: | Abstract The ability to perceive and respond to threatening situations is vital for animal survival. Defensive behaviours, including fighting, fleeing, and freezing, are employed across taxonomic groups and can vary based on the characteristics of the threat stimulus and the animal's internal state. Previous research has indicated that defensive responses in animals, including fruit flies, are often accompanied by distinct changes in cardiac activity. Flight-or-flee behaviours have been associated with increased cardiac activity while freezing response is characterized by a decreased cardiac activity. The evolutionary convergence of cardiac changes suggests an underlying physiological mechanism that contributes to behavioural responses to threats. However, the specific role of cardiac activity in shaping defensive behaviours and the molecular pathways involved remain poorly understood. In this study, we focus on loom-triggered defensive behaviours and the cardiac changes associated with them in Drosophila melanogaster. We investigate the role of the cardioacceleratory neuropeptide CCAP (crustacean cardioactive peptide) in modulating cardiac activity and its impact on behaviour during threat perception. Using the GAL/UAS system and RNA interference methodology, we aimed to impair the expression of the CCAP receptor (CCAPR) specifically in cardiomyocytes of Drosophila melanogaster. We analysed the behaviour of tethered flies walking on a ball before and after inescapable threat stimulation (looming stimulus), thus evaluating the effect of CCAPR knockdown on basal cardiac activity and during threat stimulation. Our findings reveal that CCAP signalling plays a significant role in regulating the two main features of Drosophila cardiac activity during baseline. We find that flies expressing the CCAPR RNAi (CCAPR RNAi flies) show slower and more variable heart rate (heart beating rate) and faster cardiac reversal rate (the rate of alternation between beating in the backward and forward direction) than control flies. Upon stimulation, two states of freezing were observed (quiescent and twitching freezing) and were accompanied by different cardiac dynamics. Intriguingly, flies with CCAPR RNAi showed reduced sustainability of the bradycardia during freezing, aligned to a disruption in the sustainability of quiescent freezing behaviour. This hypothesis would agree with unpublished data from the lab that shows that freely walking CCAPR RNAi flies present reduced freezing response. Though a leaky expression of the tinGal4 driver in the Nervous System might underly the reduced freezing sustainability, this research contributes to understanding the interplay between physiological and behavioural responses to threats, shedding light on evolutionary and adaptive mechanisms underlying defensive behaviours in Drosophila melanogaster. |
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