The alpha-2A adrenoceptor agonist guanfacine regulates traumatic stress processing in juvenile zebrafish

Introduction: Early-life stress (ELS), including traumatic events during vulnerable developmental periods, leads to adverse psychobiological outcomes. Although the underlying mechanisms remain unclear, dysregulated noradrenergic processing of trauma is proposed to play a role. Therefore, guanfacine, a centrally acting selective alpha-2A adrenoceptor agonist that blunts noradrenergic signalling, may be useful for attenuating ELS-related consequences. We explored this notion in zebrafish (Danio rerio), a well-established model with strong translational relevance for investigating human stress-related disorders.

Aim: The goal of this research was to explore the immediate behavioural impact of a traumatic ELS exposure and the modulatory effects of guanfacine treatment on anxiety-like behaviour in juvenile zebrafish using the open field test (OFT).

Methods: Ninety-six (96) zebrafish (30 days post-fertilisation [dpf]; both sexes; ethics approval number: NWU-00754-22-A5) were exposed to either a no-stress or stress protocol (n = 48 per group). Groups were further subdivided and exposed to normal system water (control) or guanfacine (20 µg/L) via aqueous immersion for 65 min during no-stress or stress exposure (n = 24 per group). The stress protocol consisted of sequential overcrowding, mechanical stirring, conspecific alarm substance exposure, water drainage, and air exposure, applied over 65 min. At 31 dpf, zebrafish were assessed in the OFT for 6 min. Distance travelled (cm) and freezing duration (sec) were measured. Data were analysed by two-way ANOVA (independent factors: stress exposure and treatment). Bonferroni post-hoc tests and Cohen’s d effect size calculations informed the significance and magnitude of pairwise differences.

Results: For total distance travelled, a significant interaction between stress exposure and treatment was found (p < 0.0001), with a significant main effect of treatment (p = 0.001), but not stress (p = 0.281). Guanfacine in the absence of stress significantly reduced the distance travelled compared to both the control (p < 0.0001; d = 1.5) and stress-plus-guanfacine groups (p = 0.001; d = 1.5). For freezing duration, there was a significant stress exposure-treatment interaction (p < 0.0001), and main effects of stress (p = 0.003) and treatment (p = 0.002). Guanfacine in the absence of stress significantly increased the freezing duration compared to both the control (p < 0.0001; d = 1.7) and stress-plus-guanfacine groups (p < 0.0001; d = 1.5). Freezing duration was similar across control, stress-alone, and stress-plus-guanfacine groups (p > 0.05).

Conclusion: This study is first to show that traumatic stress only modestly impacts the immediate anxiety-like behaviours of juvenile zebrafish, while guanfacine has distinct stress-dependent effects on behaviour. Guanfacine elicits anxiety-like behaviours under conditions of novelty (i.e., testing in the absence of a prior traumatic experience), but has the opposite effect in trauma-exposed fish. These findings suggest that the presence of evolutionary conserved neurobiological mechanisms in juvenile zebrafish may blunt the impact of traumatic events and provide a novel basis for investigating adrenergic mechanisms underlying ELS.

References

No references