Long-term anoxia in crucian carp: changes in the levels of amino acid and monoamine neurotransmitters in the brain, catecholamines in chromaffin tissue, and liver glycogen

Abstract

Crucian carp (Carassius carassius L.), which are extremely anoxia-tolerant, were exposed to 17 days of anoxia at 8 degrees C. One group of fish was transferred to normoxic water for 1–8 h immediately after the anoxic period. All the eight amino acids measured in brain (including four putative neurotransmitters) were more or less strongly affected by anoxia. Gamma-aminobutyric acid (GABA) displayed a nearly fivefold increase during anoxia. It is hypothesized that the increased level of this inhibitory transmitter, maybe in combination with the decrease seen in excitatory amino acids (glutamate and aspartate), causes a lowered brain activity and, hence, is a key factor behind the decrease in physical activity and systemic energy metabolism seen in anoxic Carassius. The brain levels of serotonin, dopamine and norepinephrine were remarkably well preserved after anoxia (although their synthesis is oxygen-dependent), suggesting adaptive mechanisms. However, anoxia reduced the norepinephrine level in kidney (chromaffin tissue) by 92% and, in contrast to previous results on shorter anoxic periods (3–7 days), the peripheral catecholamine store showed little sign of recovery during the subsequent normoxia. Anoxia was found to deplete the liver glycogen store severely, and the few fish that died after 15–17 days of anoxia contained no detectable liver glycogen.

Neurotoxicity in zebrafish exposed to carbon nanotubes: Effects on neurotransmitters levels and antioxidant system

“…Neurotransmitters such as dopamine (DA), serotonin (5HT) and acetylcholine (ACh) are essential regulators of brain functions (Nilsson, 1990;Almeida et al, 2003) and alterations of neurotransmitters and their metabolites has been used as an indicator of toxicity in the central nervous system (CNS) (Wang et al, 2009a(Wang et al, , 2009bPowers et al, 2011). As in the case of increased DA and 5HT levels found here, intranasal instilled copper nanoparticles (Cu NPs) in mice increased DA levels in the striatum, cerebral cortex, cerebellum, and the hippocampus.…”

Fipronil impairs the GABAergic brain responses of Nile Tilapia during the transition from normoxia to acute hypoxia

“…In general, anoxia induces increased GABA levels and GABAergic activity in the brains of vertebrate species that tolerate prolonged periods of oxygen depletion, such as fish of the genus Carassius and freshwater turtles of genera Chrysemys and Trachemys. For example, while crucian carp brains show a doubling of extracellular GABA levels after 6 h of anoxia and a fivefold increase in tissue GABA levels after prolonged anoxia (Nilsson, 1990), freshwater turtle brains show an 80‐fold increase in extracellular GABA levels after 6 h of anoxia (Nilsson & Lutz, 1991). Contrary to these prolonged hypoxia effects, we found opposite effects of acute hypoxia on the gene transcription of the ionotropic ( GABA A‐γ ) and metabotropic ( GABA B1 ) receptors, the first one presenting decreased values under hypoxic conditions for 3 h (~2.0 mg.L −1 or PwO 2 ~ 35 mmHg), regardless of any interaction effect with the other predictors tested.…”

De novo assembly and analysis of the transcriptome of the Siberian wood frog Rana amurensis

“…G.E. Nilsson et al (1990Nilsson et al ( , 1991 found that levels of different neurotransmitters in the brain and other organs changed significantly upon exposure to hypoxia: the concentrations of GABA increased, and those of glutamate decreased in the crucian carp and the red-eared slider turtle, but not in the hypoxia-intolerant species. The authors also found that the levels of serotonin, dopamine, and norepinephrine remained unchanged, although their synthesis is oxygen-dependent.…”

“…Brain and heart are the most sensitive to hypoxia (Nilsson et al, 2015;Swenson, 2016), so we used transcripts from these organs for transcriptome construction. To test the assembled transcriptome, we also performed a search for neurotransmitter receptor genes: it was demonstrated (Nilsson et al, 1990(Nilsson et al, , 1991 that neurotransmitters mediate hypoxia response in turtles, so we hypothesized that this might also be true for the Siberian wood frog.…”