Some Environmental Contaminants Influence Motor and Feeding Behaviors in the Ornate Wrasse ( Thalassoma pavo ) via Distinct Cerebral Histamine Receptor Subtypes

Abstract

Common environmental contaminants such as heavy metals and pesticides pose serious risks to behavioral and neuroendocrine functions of many aquatic organisms. In the present study, we show that the heavy metal cadmium and the pesticide endosulfan produce such effects through an interaction of specific cerebral histamine receptor subtypes in the teleost ornate wrasse (Thalassoma pavo). Treatment of this teleost with toxic cadmium levels for 1 week was sufficient to induce abnormal swimming movements, whereas reduced feeding behaviors were provoked predominantly by elevated endosulfan concentrations. In the brain, these environmental contaminants caused neuronal degeneration in cerebral targets such as the mesencephalon and hypothalamus, damage that appeared to correlate with altered binding levels of the three major histamine receptors (subtypes 1, 2, and 3). Although cadmium accounted for reduced binding activity of all three subtypes in most brain regions, it was subtype 2 that seemed to be its main target, as shown by a very great (p < 0.001) down-regulation in mesencephalic areas such as the stratum griseum central layer. Conversely, endosulfan provided very great and great (p < 0.01) up-regulating effects of subtype 3 and 1 levels, respectively, in preoptic-hypothalamic areas such as the medial part of the lateral tuberal nucleus, and in the suprachiasmatic nucleus. These results suggest that the neurotoxicant-dependent abnormal motor and feeding behaviors may well be tightly linked to binding activities of distinct histamine subtypes in localized brain regions of the Thalassoma pavo.

Toxicity of endosulfan on embryo‐larval development of the South American toad Rhinella arenarum

“…Furthermore, we confirm and extend results of previous studies on neurotoxicity, such as as lack of correct equilibrium and lying on the lateral side, swirling, nonfeeding behavior, and extensive paralysis [14,35]. The neurotoxicity effect could be associated with the increased synaptic concentrations of several neurotransmitters, including the decreased acetylcholinesterase activity as observed in wild frogs exposed to endosulfan [36] as well as the neuronal degeneration in cerebral targets, such as the mesenencephalon and hypothalamus reported for endosulfanexposed fish [37]. Behavioral markers have relevant potential as early warning systems when other toxicity parameters such as mortality are absent.…”

Using sets of behavioral biomarkers to assess short-term effects of pesticide: a study case with endosulfan on frog tadpoles

“…First, inhibition of acetylcholinesterase disturbs neurotransmission, particularly in muscles, and thus could affect locomotory performance such as found in shrimp ). Second, neuronal degeneration in cerebral targets, such as the mesenencephalon and hypothalamus, was also highlighted with associated altered binding levels at major histamine receptors in fish (Giusi et al 2005).…”

The Effect of Cadmium Absorption on Ghrelin and Malondialdehyde Levels in White Rats (Rattusnorvegicus)

“…Other studies have suggested that heavy metal cadmium increased lipid peroxidation in the liver through the formation of Reactive Oxygen Species (ROS). The same damage also appears to be associated with dysfunction of neurons in the hypothalamus, pituitary and testis [18]. It is also explained that cadmium toxicity occurs through its ability to induce the formation of free radicals indirectly, including superoxide radicals, hydroxyl radicals, and nitric oxide.…”