scholarly journals GABA receptors in the olfactory epithelium of the gilthead seabream (Sparus aurata)

Author(s):  
Rita A. Costa ◽  
Zélia Velez ◽  
Peter C. Hubbard

Exposure to high PCO2/low pH seawater induces behavioural alterations in fish; a possible explanation for this is a reversal of Cl−/HCO3− currents through GABAA receptors (the GABAA receptor theory). However, the main evidence for this is that gabazine, a GABAA receptor antagonist, reverses these effects when applied to the water, assuming that exposure to systems other than the CNS would be without effect. Here, we show the expression of both metabotropic and ionotropic GABA receptors, and the presence of GABAA receptor protein, in the olfactory epithelium (OE) of gilthead seabream. Furthermore, exposure of the OE to muscimol (a specific GABAA receptor agonist) increases or decreases the apparent olfactory sensitivity to some odorants. Thus, although the exact function of GABAA receptors in the OE is not yet clear, this may complicate the interpretation of studies wherein water-borne gabazine is used to reverse the effects of high CO2 levels on olfactory-driven behaviour in fish.

1996 ◽  
Vol 270 (6) ◽  
pp. C1726-C1734 ◽  
Author(s):  
M. Shimura ◽  
N. Harata ◽  
M. Tamai ◽  
N. Akaike

The gamma-aminobutyric acid (GABA)-induced response was investigated in acutely dissociated suprachiasmatic nucleus (SCN) neurons of 11- to 14-day-old rats, under the voltage-clamp condition of nystatin-perforated patch recording. At a holding potential of -40 mV, application of GABA induced inward currents in a concentration-dependent manner. Pentobarbital and 5 beta-pregnan-3 alpha-ol-20-one (pregnanolone) similarly induced inward currents. GABA-induced inward currents were suppressed in a concentration-dependent manner by pretreating neurons with a GABAA receptor antagonist, bicuculline. Bicuculline (3 x 10(-6) M) shifted the concentration-response curve of GABA to the left in a competitive manner. Reversal potential of the GABA response (EGABA) was -3.4 +/- 0.7 mV, close to the theoretical Cl- equilibrium potential of -4.1 mV. Pretreating SCN neurons with diazepam, pentobarbital, and pregnanolone enhanced the 3 x 10(-6) M GABA response. Diazepam (3 x 10(-8) M), pentobarbital (3 x 10(-5) M), and pregnanolone (10(-7) M) shifted the concentration-response curve of GABA to the left without changing the maximal amplitude of GABA responses. EGABA in the presence of diazepam, pentobarbital, or pregnanolone was the same as that in their absence. These results show that the GABA response in acutely dissociated SCN neurons is mediated by the GABAA receptor. Because the GABAA receptor of SCN neurons is allosterically augmented by diazepam, pentobarbital, and pregnanolone, similarly as in other regions of the central nervous system, the present study opens up ways to functionally modulate the GABAA receptors in SCN.


2000 ◽  
Vol 203 (24) ◽  
pp. 3821-3829 ◽  
Author(s):  
P.C. Hubbard ◽  
E.N. Barata ◽  
A.V. Canario

Estuarine and/or migratory teleosts may experience large and rapid changes in external [Ca(2+)]. Previous studies have largely centred on the physiological mechanisms that maintain a constant plasma [Ca(2+)] in the face of such external fluctuations, but little work has been directed to examining how these changes may originally be detected. We present evidence that the olfactory system of the gilthead seabream (Sparus aurata) is highly sensitive to reductions in environmental [Ca(2+)] and suggest a possible mechanism by which this may be mediated. Multi-unit extracellular recordings were made from the olfactory nerve of Sparus aurata while the [Ca(2+)] of artificial sea water flowing over the olfactory epithelium was varied from 10 to 0 mmol l(−)(1). Reductions in [Ca(2+)] caused a large, non-accommodating increase in the firing rate of the olfactory nerve (apparent IC(50)=1.67+/−0.26 mmol l(−)(1), apparent Hill coefficient=−1.22+/−0.14; means +/− s.e.m., N=6). This response was not due to the concomitant reduction in osmolality and was specific for Ca(2+). During continuous exposure of the olfactory epithelium to Ca(2+)-free sea water, the apparent IC(50) and Hill coefficient in response to increases in [Ca(2+)] were 0.48+/−0.14 mmol l(−)(1) and −0.76+/−0.16 (means +/− s.e.m., N=6), respectively, suggesting an adaptation of the Ca(2+)-sensing system to low-[Ca(2+)] environments. Ca(2+) is intimately involved in signal transduction in the olfactory receptor neurones, but our data support a true olfactory response, rather than a non-specific effect to lowering of external [Ca(2+)]. The absence of Ca(2+) from sea water only partially and temporarily blunted the olfactory response to the odorant l-serine; the response amplitude recovered to control levels within 20 min. This suggests that the olfactory system in general is able to adapt to low-[Ca(2+)] environments. We suggest that the Ca(2+)sensitivity is mediated by an extracellular Ca(2+)-sensing receptor similar to the recently characterized mammalian Ca(2+)-sensing receptor.


1995 ◽  
Vol 73 (3) ◽  
pp. 1135-1144 ◽  
Author(s):  
S. J. Zhang ◽  
M. B. Jackson

1. We investigated gamma-aminobutyric acid (GABA) receptors using thin slice patch-clamp techniques in the swellings along axons of posterior pituitary nerve terminals. 2. Activation of the nerve terminal GABAA receptor induced a mean conductance change of 1.5 nS. Normalizing to area gave a mean conductance density of 0.38 mS/cm2. 3. Whereas GABAA receptor-mediated responses could be seen in 91% of the nerve terminals tested, GABAB receptor-mediated responses could not be detected. The GABAB receptor agonist baclofen had no effect on holding current or on voltage-activated K+ and Ca2+ channels. It is unlikely that nerve terminals of the posterior pituitary contain GABAB receptors. 4. The channel gated by the nerve terminal GABAA receptor exhibited only a single open conductance level. Only fully open and fully closed states were observed. Subconductance states typical of other GABAA receptor channels were not seen in the GABA-gated channels of posterior pituitary nerve terminals. 5. Both open time and closed time distributions were biexponential, indicating at least two open and two closed conformations of the channel. At a higher GABA concentration, long-duration openings predominated, suggesting that long-duration openings were distinguished from short-duration openings by the occupation of a greater number of agonist binding sites. 6. Sustained application of GABA desensitized the receptor with simple exponential kinetics. The time constant for desensitization was approximately 9 s for both GABA and muscimol. 7. Zinc ions at concentrations of 100 microM reduced GABA responses by only 22%. This weak sensitivity to zinc, together with a previous observation of benzodiazepine sensitivity, suggested that the nerve terminal GABAA receptor possesses a gamma-subunit. 8. Responses mediated by the GABAA receptor persist in whole terminal recordings without Mg-ATP in the pipette solution. Thus, in contrast to many other GABAA receptors, this receptor showed no rundown in the absence of ATP. 9. The GABAA receptor channel of posterior pituitary nerve terminals has many properties in common with GABAA receptors of other preparations. A number of subtle differences between the nerve terminal receptor described here and cell body receptors described elsewhere may reflect the presence of receptor protein subunits unique to nerve terminals.


Molecules ◽  
2021 ◽  
Vol 26 (23) ◽  
pp. 7108
Author(s):  
Byungjick Min ◽  
Yejin Ahn ◽  
Hyeok-Jun Cho ◽  
Woong-Kwon Kwak ◽  
Hyung Joo Suh ◽  
...  

Hops contain flavonoids that have sedative and sleep-promoting activities such as α-acid, β-acid, and xanthohumol. In this study, the sleep-enhancing activity of a Saaz–Saphir hops mixture was measured. In the caffeine-induced insomnia model, the administration of a Saaz–Saphir mixture increased the sleep time compared to Saaz or Saphir administration alone, which was attributed to the increase in NREM sleep time by the δ-wave increase. Oral administration of the Saaz–Saphir mixture for 3 weeks increased the γ-amino butyric acid (GABA) content in the brain and increased the expression of the GABAA receptor. As the GABA antagonists picrotoxin and bicuculline showed a decrease in sleep activity, it was confirmed that the GABAA receptor was involved in the Saaz–Saphir mixture activity. In addition, the GABAA receptor antagonist also reduced the sleep activity induced by xanthohumol and humulone contained in the Saaz–Saphir mixture. Therefore, xanthohumol and humulone contained in the Saaz–Saphir mixture showed sleep-promoting activity mediated by the GABAA receptors. The mixture of the Saaz and Saphir hop varieties may thus help mitigate sleep disturbances compared to other hop varieties.


Aquaculture ◽  
2021 ◽  
Vol 537 ◽  
pp. 736462
Author(s):  
I. Elalfy ◽  
H.S. Shin ◽  
D. Negrín-Báez ◽  
A. Navarro ◽  
M.J. Zamorano ◽  
...  

2021 ◽  
Author(s):  
José Carlos Campos‐Sánchez ◽  
Francisco A. Guardiola ◽  
José María García Beltrán ◽  
Diana Ceballos‐Francisco ◽  
María Ángeles Esteban

Animals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 753
Author(s):  
Andre Barany ◽  
Juan Fuentes ◽  
Gonzalo Martínez-Rodríguez ◽  
Juan Miguel Mancera

Several studies in fish have shown that aflatoxin B1 (AFB1) causes a disparity of species-dependent physiological disorders without compromising survival. We studied the effect of dietary administration of AFB1 (2 mg AFB1 kg−1 diet) in gilthead seabream (Sparus aurata) juveniles in combination with a challenge by stocking density (4 vs. 40 g L−1). The experimental period duration was ten days, and the diet with AFB1 was administered to the fish for 85 days prior to the stocking density challenge. Our results indicated an alteration in the carbohydrate and lipid metabolites mobilization in the AFB1 fed group, which was intensified at high stocking density (HSD). The CT group at HSD increased plasma cortisol levels, as expected, whereas the AFB1-HSD group did not. The star mRNA expression, an enzyme involved in cortisol synthesis in the head kidney, presented a ninefold increase in the AFB1 group at low stocking density (LSD) compared to the CT-LSD group. Adenohypophyseal gh mRNA expression increased in the AFB1-HSD but not in the CT-HSD group. Overall, these results confirmed that chronic AFB1 dietary exposure alters the adequate endocrinological physiological cascade response in S. aurata, compromising the expected stress response to an additional stressor, such as overcrowding.


Animals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 519
Author(s):  
Shajahan Ferosekhan ◽  
Serhat Turkmen ◽  
Cathaysa Pérez-García ◽  
Hanlin Xu ◽  
Ana Gómez ◽  
...  

Genetic selection in gilthead seabream (GSB), Sparus aurata, has been undertaken to improve the growth, feed efficiency, fillet quality, skeletal deformities and disease resistance, but no study is available to delineate the effect of genetic selection for growth trait on GSB reproductive performance under mass spawning condition. In this study, high growth (HG) or low growth (LG) GSB broodstock were selected to evaluate the sex steroid hormones, sperm, egg quality and reproductive performance under different feeding regime of commercial diet or experimental broodstock diet containing either fish oil (FO) or vegetable oil (VO) based diet. Under commercial diet feeding phase, broodstock selected for either high growth or low growth did not show any significant changes in the egg production per kg female whereas egg viability percentage was positively (p = 0.014) improved by the high growth trait broodstock group. The experimental diet feeding results revealed that both growth trait and dietary fatty acid composition influenced the reproductive performance of GSB broodstock. In the experimental diet feeding phase, we observed high growth trait GSB males produced a higher number of sperm cells (p < 0.001) and also showed a higher sperm motility (p = 0.048) percentage. The viable egg and larval production per spawn per kg female were significantly improved by the broodstock selected for high growth trait and fed with fish oil-based diet. This present study results signifies that gilthead seabream broodstock selected on growth trait could have positive role in improvement of sperm and egg quality to produce viable progeny.


2021 ◽  
Vol 22 (13) ◽  
pp. 7141
Author(s):  
Carmen González-Fernández ◽  
Francisco Guillermo Díaz Baños ◽  
María Ángeles Esteban ◽  
Alberto Cuesta

Nanoplastics (NPs) are one of the most abundant environment-threatening nanomaterials on the market. The objective of this study was to determine in vitro if functionalized NPs are cytotoxic by themselves or increase the toxicity of metals. For that, we used 50 nm polystyrene nanoparticles with distinct surface functionalization (pristine, PS-Plain; carboxylic, PS-COOH; and amino PS-NH2) alone or combined with the metals arsenic (As) and methylmercury (MeHg), which possess an environmental risk to marine life. As test model, we chose a brain-derived cell line (SaB-1) from gilthead seabream (Sparus aurata), one of the most commercial fish species in the Mediterranean. First, only the PS-NH2 NPs were toxic to SaB-1 cells. NPs seem to be internalized into the cells but they showed little alteration in the transcription of genes related to oxidative stress (nrf2, cat, gr, gsta), cellular protection against metals (mta) or apoptosis (bcl2, bax). However, NPs, mainly PS-COOH and PS-NH2, significantly increased the toxicity of both metals. Since the coexistence of NPs and other pollutants in the aquatic environment is inevitable, our results reveal that the combined effect of NPs with the rest of pollutants deserves more attention.


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