Abstract
Serotonin (5-hydroxytryptamine, 5-HT) is acknowledged as a major neuromodulator of nervous systems in both invertebrates and vertebrates. It has been proposed for several decades that it impacts animal cognition and behavior. In spite of a completely distinct organization of the 5-HT systems across the animal kingdom, several lines of evidence suggest that the influences of 5-HT on behavior and cognition are evolutionary conserved. In this review, we have selected some behaviors classically evoked when addressing the roles of 5-HT on nervous system functions. In particular, we focus on the motor activity, arousal, sleep and circadian rhythm, feeding, social interactions and aggressiveness, anxiety, mood, learning and memory, or impulsive/compulsive dimension and behavioral flexibility. The roles of 5-HT, illustrated in both invertebrates and vertebrates, show that it is more able to potentiate or mitigate the neuronal responses necessary for the fine-tuning of most behaviors, rather than to trigger or halt a specific behavior. 5-HT is, therefore, the prototypical neuromodulator fundamentally involved in the adaptation of all organisms across the animal kingdom.
Highlights
Serotonin (5-hydroxytryptamine, 5-HT) is a neuromodulator present in most animal phyla, the overall function of this small molecule is still poorly understood
All three d5-HTRs expressed in MBs decrease locomotor activity in fly larvae, the activation of d5-HT1B in other central nervous system (CNS) regions may counteract its own action in the MBs [81]
Several 5-HT receptors (5-HTRs) including 5-HT1AR, 5-HT1BR, 5-HT2AR, 5-HT2BR, 5-HT2CR, 5-HT3R, 5-HT4R, and 5-HT7Rs participate in anxiety-like responses and both agonists and antagonists can be used depending on the subtype to regulate anxiety-like behaviors [172]
Summary
Serotonin (5-hydroxytryptamine, 5-HT) is a neuromodulator present in most animal phyla, the overall function of this small molecule is still poorly understood. The diversity of modulating effects induced by 5-HT in cognitive tasks and behavioral responses is linked to i) its simultaneous effects on a multiplicity of neural targets underlying these functions and ii) to the large number of its receptors with their intracellular signaling pathways and their different affinities, acting at various neuron locations. Because of these specificities, 5-HT systems can ensure fine-tuning of behaviors in various situations, sometimes by inhibiting learned behavioral responses that would be inappropriate or by adjusting the timing of responses to ensure more adapted behavior [5,6].
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
