Left Habenular Activity Attenuates Fear Responses in Larval Zebrafish

Abstract

Summary Fear responses are defensive states that ensure survival of an organism in the presence of a threat. Perception of an aversive cue causes changes in behavior and physiology, such as freezing and elevated cortisol, followed by a return to the baseline state when the threat is evaded [1]. Neural systems that elicit fear behaviors include the amygdala, hippocampus and medial prefrontal cortex. However, aside from a few examples, little is known about brain regions that promote recovery from an aversive event [2]. Previous studies had implicated the dorsal habenular nuclei in regulating fear responses and boldness in zebrafish [3–7]. We now show that perturbation of the inherent left-right (L-R) asymmetry of the dorsal habenulo-interpeduncular (dHb-IPN) pathway at larval stages expedites the return of locomotor activity following an unexpected negative stimulus, electric shock. Severing habenular efferents to the IPN, or only those from the left dHb, prolongs the freezing behavior that follows shock. Individuals with symmetric, right isomerized dHb also exhibit increased freezing. In contrast, larvae that have symmetric, left-isomerized dHb, or in which just the left dHb-IPN projection is optogenetically activated, rapidly resume swimming post shock. In vivo calcium imaging reveals a neuronal subset, predominantly in the left dHb, whose activation is correlated with resumption of swimming. The results demonstrate functional specialization of the left dHb-IPN pathway in attenuating the response to fear.

A novel conserved enhancer at zebrafish zic3 and zic6 loci drives neural expression

“…[36][37][38] The habenula in zebrafish is subdivided into the dorsal and ventral habenula, which are homologous to lateral and medial parts in mammals. [36][37][38] The habenula in zebrafish is subdivided into the dorsal and ventral habenula, which are homologous to lateral and medial parts in mammals.…”

“…The habenula is part of a highly conserved limbic system conduction pathway in vertebrates and has been shown to play a crucial role in a diverse set of behavioral systems, including brain stimulation, endocrine function, mating, ingestion, fear responses, and olfaction. [36][37][38] The habenula in zebrafish is subdivided into the dorsal and ventral habenula, which are homologous to lateral and medial parts in mammals. 39 Within the CNS, zic3 is known to be expressed in a restricted manner during neurulation.…”

Functional properties of habenular neurons are determined by developmental stage and sequential neurogenesis

“…These results show for the first time that distinct functional clusters of spatially organized habenular neurons are born at a distinct developmental stage, and exhibit similar features of spontaneous activity. Accumulating evidence suggest that the distinct functional clusters of habenular neurons mediate distinct behaviours (Agetsuma et al, 2010;Amo et al, 2014;Andalman et al, 2019;Chou et al, 2016;Duboue et al, 2017;Lee et al, 2010). Sequential addition of new functional clusters with new properties across development could therefore explain the expansion of zebrafish behavioural repertoire across development (Dreosti et al, 2015;Valente et al, 2012).…”

“…While the majority of studies have focused on studying activity-dependent processes in the development of sensory systems, less is known about the maturation of higher brain areas integrating information from multiple brain regions, such as the habenula. The habenula is a particularly interesting brain region, as it was shown to integrate both sensory Miyasaka et al, 2009;Zhang et al, 2017) and cortico-limbic inputs (Herkenham and Nauta, 1977;Hong et al, 2011;Lazaridis et al, 2019;Matsumoto and Hikosaka, 2007;Meye et al, 2016;Okamoto et al, 2012;Stamatakis et al, 2013;Turner et al, 2016;Warden et al, 2012) while directly regulating the function of monoaminergic brain nuclei controlling behaviour (Duboue et al, 2017;Flanigan et al, 2017;Hikosaka, 2010;Krishnan et al, 2014;Lin and Jesuthasan, 2017;Matsumoto and Hikosaka, 2007;Zhang et al, 2017). Dysfunction of the habenula is also shown to be associated with several neurological conditions and mood disorders including depression (Huang et al, 2019;.…”

“…Two major subnuclei, the lateral and medial habenula in mammals, respectively dorsal habenula (dHb) and ventral habenula (vHb) in zebrafish, have clear differences in their functional and molecular profiles (Amo et al, 2014;Lee et al, 2010). While the dHb is involved in sensory processing Zhang et al, 2017), circadian rhythms , aggression (Chou et al, 2016) and experience dependent fear response (Agetsuma et al, 2010;Duboue et al, 2017;Lee et al, 2010), the vHb was shown to play a role in avoidance learning (Amo et al, 2014) and active coping behaviour (Andalman et al, 2019). In zebrafish, dHb and vHb originate from separate neural progenitor pools, and were suggested to maturate at distinct developmental time points (Beretta et al, 2013).…”