Stimulation of dopamine D ₁ receptor improves learning capacity in cooperating cleaner fish

Abstract

Accurate contextual decision-making strategies are important in social environments. Specific areas in the brain are tasked to process these complex interactions and generate correct follow-up responses. The dorsolateral and dorsomedial parts of the telencephalon in the teleost fish brain are neural substrates modulated by the neurotransmitter dopamine (DA), and are part of an important neural circuitry that drives animal behaviour from the most basic actions such as learning to search for food, to properly choosing partners and managing decisions based on context. The Indo-Pacific cleaner wrasse Labroides dimidiatus is a highly social teleost fish species with a complex network of interactions with its 'client' reef fish. We asked if changes in DA signalling would affect individual learning ability by presenting cleaner fish two ecologically different tasks that simulated a natural situation requiring accurate decisionmaking. We demonstrate that there is an involvement of the DA system and D 1 receptor pathways on cleaners' natural abilities to learn both tasks. Our results add significantly to the growing literature on the physiological mechanisms that underlie and facilitate the expression of cooperative abilities.

The Integration of Sociality, Monoamines, and Stress Neuroendocrinology in Fish Models: Applications in the Neurosciences

“…Moreover, D1 blockage seems also to be related to an increase of novelty seeking behaviour in cleaners (Soares et al, 2017b). On the other hand, the increase of DA activity seems to enable cleaners learning abilities (Messias et al, 2016b), being that this so-called motivational increase to learning new tasks could be coupled with an increase of stress levels, which at this point is purely speculative. Interestingly, when signal and reward differ (in time and space), a scenario that in natural conditions would occur when a situation of an observing bystander client, DA blockage reduces cleaner impulsiveness towards the sign (sign-tracking response, see Soares et al (Soares et al, 2017a)), which suggests that stresscontrol mechanisms should also be in place.…”

“…Naturally, because the functions of the dopaminergic (DA) system are multiple, involving decision-making, learning and reward mechanisms (for example, Messias et al (2016aMessias et al ( , 2016b; Schultz (2002Schultz ( , 2006; Soares (2017)), the relationship between dopamine and stress will also be complex, contextual and brain-region specific. As such, the DA system should respond differently to distinct types of stressors as it confers to animals the ability to discriminate between (Pani et al, 2000).…”

Gene expression correlates of social evolution in coral reef butterflyfishes

“…Hence, C. lunulatus pair bonding might also rely on the learned association between partner (conditioned stimulus) and food (natural reward/unconditioned stimulus), and this associative learning might also be underpinned by dopamine acting upon reward circuitry. In support of this idea, in teleosts, both DA-D1R and -D2R binding are critical for psychostimulant/food reward learning 76,77,[166][167][168][169] and a network structured very similarly to the amniote mesolimbic reward system has been identified 88,89 . Importantly, almost all of the brain regions that were associated with DA-mediated pair bonding in this study are nodes of this putative teleost mesolimbic reward system (POA notwithstanding).…”

The Integration of Sociality, Monoamines, and Stress Neuroendocrinology in Fish Models: Applications in the Neurosciences

“…Moreover, D1 blockage seems also to be related with an increase of novelty seeking behaviour in cleaners (Soares et al, 2017b). On the other hand, the increase in DA activity seems to enable the learning abilities of cleaners (Messias et al, 2016b); this so-called motivational increase to learn new tasks could be coupled with an increase of stress levels, but at this point is purely speculative. Interestingly, when signal and reward differ (in time and space), a scenario that in natural conditions occurs when cleaners are being observed by other potential clients (bystanders) that are yet to decide whether or not to visit, DA blockage seems 34 to reduce cleaner impulsiveness towards the signal, enabling them to continue their current interactions while waiting for those bystanders to finally visit and solicit to be cleaned (see Soares et al, 2017a)), which suggests that stress-control mechanisms should also be in place.…”

“…Naturally, because the functions of the dopaminergic (DA) system are multiple, involving decision-making, learning and reward mechanisms (for example, Messias et al (2016aMessias et al ( , 2016b; Schultz (2002Schultz ( , 2006; Soares (2017)), the relationship between dopamine and stress will also be complex, contextual and brain-region specific. As such, the DA system should respond differently to distinct types of stressors as it confers to animals the ability to discriminate between change-related stimuli (Pani et al, 2000).…”