Abstract
The olfactory system, composed of the olfactory organs and the olfactory bulb, allows organisms to interact with their environment and through the detection of odor signals. Olfaction mediates behaviors pivotal for survival, such as feeding, mating, social behavior, and danger assessment. The olfactory organs are directly exposed to the milieu, and thus are particularly vulnerable to damage by environmental pollutants and toxicants, such as heavy metals, pesticides, and surfactants, among others. Given the widespread occurrence of olfactory toxicants, there is a pressing need to understand the effects of these harmful compounds on olfactory function. Zebrafish (Danio rerio) is a valuable model for studying human physiology, disease, and toxicity. Additionally, the anatomical components of the zebrafish olfactory system are similar to those of other vertebrates, and they present a remarkable degree of regeneration and neuroplasticity, making it an ideal model for the study of regeneration, reorganization and repair mechanisms following olfactory toxicant exposure. In this review, we focus on (1) the anatomical, morphological, and functional organization of the olfactory system of zebrafish; (2) the adverse effects of olfactory toxicants and injury to the olfactory organ; and (3) remodeling and repair neuroplasticity mechanisms following injury and degeneration by olfactory toxicant exposure.
Highlights
The olfactory system plays a pivotal role in animal survival since it detects and discriminates myriad odor signals and mediates important behaviors such as foraging, mating, social behavior, and assessing danger [1,2]
The olfactory organ of zebrafish includes epithelium arranged in several lamellae that converge in a central non-sensory raphe, forming a bilaterally symmetrical, cup-shaped structure known as the rosette
These studies clearly show that exposure to waterborne heavy metals produce significant damage of the olfactory organ leading to olfactory dysfunction in zebrafish, with bile salt-sensing ciliated olfactory sensory neurons (OSNs) presenting the most susceptibility to the effects of some of these neurotoxicant agents (Figure 3A, Table 1)
Summary
The olfactory system plays a pivotal role in animal survival since it detects and discriminates myriad odor signals and mediates important behaviors such as foraging, mating, social behavior, and assessing danger [1,2]. Zebrafish is an ideal model for studying the olfactory system, since its anatomical components are more accessible in this animal than other vertebrates This makes the zebrafish olfactory system very amenable to experimental manipulations with less invasive techniques, increasing the rate of survival and recovery [10,11,17,18,19]. Another key characteristic of zebrafish is that it presents a high degree of central nervous system (CNS) regeneration, including the olfactory system, following damage [18,20,21,22,23,24,25] This feature makes the olfactory system of zebrafish an ideal model for the study of regeneration, reorganization, and repair mechanisms following toxicant exposure or direct injury. This review will serve as a foundation for the use of zebrafish as a useful and robust model for assessing the effects of olfactory toxicants and injury
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