Predator odor produces anxiety-like behavioral phenotype in planarians that is counteracted by fluoxetine

Abstract

Avoidant behavior is a characteristic feature post-traumatic stress disorder (PTSD) and is modeled in mammals with predator odor. Light avoidance is a hallmark behavioral reaction in planarians. We hypothesized that planarians exposed to frog extract would display enhanced light avoidance that is prevented by fluoxetine. Enhanced light avoidance (i.e., less time spent in light compartment of a dish split into light and dark sides) after a 30-min frog extract exposure (0.0001-0.01%) manifested 15 min post-exposure, persisted for at least 24 h, and was counteracted by fluoxetine (10 μM). These results suggest conservation of an anxiety-like behavioral phenotype.

A circuit from the ventral subiculum to anterior hypothalamic nucleus GABAergic neurons essential for anxiety-like behavioral avoidance

“…Intriguingly, brief predator encounters elevate anxiety levels in species ranging from flatworms to fish, rodents, and primates 14 – 17 , pointing to an evolutionarily conserved mechanism connecting predator defense to anxiety 18 – 21 . Indeed, the Predator Imminence Continuum theory proposes three modes of defensive behaviors organized along a predator’s perceived imminence continuum (spatial/temporal distance or probability of contact) 10 , 22 , of which anxiety corresponds to the “pre-encounter” mode.…”

Limited Cheese Intake Paradigm Replaces Patterns of Behavioral Disorders in Experimental PTSD: Focus on Resveratrol Supplementation

“…Based on these measurements, the anxiety index (AI) was calculated using the formula [ 52 , 53 , 54 ]: AI = 1 − {[(time in open arms/Σ time on maze) + (number of entries into open arms/Σ number of all entries)]/2}. The AI discriminant of 0.8 was determined based on the AI distribution of naive rats measured in preliminary experiments for this study and historical AIs of control rats, as previously reported [ 25 ]. Additionally, the number of freezing acts in the EPM was also recorded.…”

“…Nowadays, selective serotonin reuptake inhibitors (SSRIs) are widely used in the treatment of PTSD, with the main target being the 5-HT transporter (SERT). Experimental PTSD models, such as the single prolonged test, have revealed that SSRIs can correct both behavioral and neurochemical abnormalities in the hippocampus [ 24 , 25 ]. It is suggested that the efficacy of SSRIs in addressing behavioral disorders is directly linked to their ability to reverse abnormalities in hippocampal neurotransmitter metabolism [ 26 ].…”

Post-SSRI Sexual Dysfunction: A Bioelectric Mechanism?

“…65 The serotonin neurotransmitter system in planaria has been characterized in numerous studies: an ortholog of the gene encoding the enzyme tryp-tophan hydroxylase which catalyzes the rate-limiting step in serotonin synthesis has been identified in Dugesia japonica, 66 planarian serotonin receptors have been characterized, 67,68 and multiples studies have found that SSRI treatment impacts planaria in numerous ways, including locomotion, light/dark preference (photophobic tendencies), DNA damage, and regenerative polarity. 65,[69][70][71] To assess the impact of transient fluoxetine treatment on bioelectric states, intact wild-type D. japonica were soaked in a 2 lM fluoxetine solution for 3 days, at which point the solution was washed out and the samples were placed in Poland Spring water for 1 week at 13°C to prevent fissioning (termed ''1wk washout'' group). Results are shown in Figure 1.…”