Pharmacological Modulation of Behaviour, Serotonin and Dopamine Levels in Daphnia magna Exposed to the Monoamine Oxidase Inhibitor Deprenyl.

Marina Bellot,Demetrio Raldúa,Cristian Gómez-Canela,Melissa Faria,Carlos Barata

doi:10.3390/toxics9080187

Abstract

This study assessed the effects of the monoamine oxidase (MAO) inhibitor deprenyl in Daphnia magna locomotor activity. The mechanisms of action of deprenyl were also determined by studying the relationship between behaviour, MAO activity and neurotransmitter levels. Modulation of the D. magna monoamine system was accomplished by 24 h exposure to two model psychotropic pharmaceuticals with antagonistic and agonistic serotonin signalling properties: 10 mg/L of 4-chloro-DL-phenylalanine (PCPA) and 1 mg/L of deprenyl, respectively. Contrasting behavioural outcomes were observed for deprenyl and PCPA reflected in decreased basal locomotor activity and enhanced habituation for the former compound and delayed habituation for the latter one. Deprenyl exposure inhibited monoamine oxidase (MAO) activity and increased the concentrations of serotonin, dopamine and the dopamine metabolite 3-methoxytyramine in whole D. magna extracts. Our findings indicate that D. magna is a sensitive and useful nonvertebrate model for assessing the effects of short-term exposure to chemicals that alter monoamine signalling changes.

Highlights

For the Daphnia photomotor response assay (DPRA) to repetitive light stimuli, absolute and proportional distances moved across the tested compounds are reported in Figure 1 and the statistics are referred to the AUC values reported in the graph inlet
We provided for the first time the results on the mode of action of deprenyl in D. magna
Deprenyl at 1 mg/L inhibited about 50% of the monoamine oxidase (MAO) activity and by doing so increased the concentrations of serotonin and dopamine by 2- and 2.4fold, respectively

Summary

Introduction

Animal behaviour to environmental stimuli changes such as predation or food availability is a key fitness trait [1]. Of particular interest are behavioural responses related to predator avoidance such as sudden locomotion changes in response to visual or tactile stimuli [2,3]. Serotonin is one of the major neurotransmitters in the central nervous system (CNS), modulating many behaviours including perception, mood, reward, anger, aggression, appetite, memory, sexuality and attention [4]. Neurological pathologies such as schizophrenia, depression and anxiety have been related to dysfunctions in the serotonergic system

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