Hindbrain neurovascular anatomy of adult goldfish (Carassius auratus)

The goldfish hindbrain develops from a segmented (rhombomeric) neuroepithelial scaffold, similar to other vertebrates. Motor, reticular and other neuronal groups develop in specific segmental locations within this rhombomeric framework. Teleosts are unique in possessing a segmental series of unpaired, midline central arteries that extend from the basilar artery and penetrate the pial midline of each hindbrain rhombomere (r). This study demonstrates that the rhombencephalic arterial supply of the brainstem forms in relation to the neural segments they supply. Midline central arteries penetrate the pial floor plate and branch within the neuroepithelium near the ventricular surface to form vascular trees that extend back towards the pial surface. This intramural branching pattern has not been described in any other vertebrate, with blood flow in a ventriculo‐pial direction, vastly different than the pial‐ventricular blood flow observed in most other vertebrates. Each central arterial stem penetrates the pial midline and ascends through the floor plate, giving off short transverse paramedian branches that extend a short distance into the adjoining basal plate to supply ventromedial areas of the brainstem, including direct supply of reticulospinal neurons. Robust r3 and r8 central arteries are significantly larger and form a more interconnected network than any of the remaining hindbrain vascular stems. The r3 arterial stem has extensive vascular branching, including specific vessels that supply the cerebellum, trigeminal motor nucleus located in r2/3 and facial motoneurons found in r6/7. Results suggest that some blood vessels may be predetermined to supply specific neuronal populations, even traveling outside of their original neurovascular territories in order to supply migrated neurons.     

Serial ablations of the telencephalon and avoidance learning by goldfish (Carassius auratus)

Simultaneous bilateral ablation of the teleost telencephalon was confirmed to dramatically impair the retention, extinction, and "reversal learning" of a preoperatively learned instrumental avoidance response in a shuttle box. The focus of the experiment was on whether two-stage serial unilateral ablations of the teleost telencephalon would ameliorate the effects seen following one-stage bilateral ablation and whether such amelioration would be a function of the fish's experiences between the staged ablations. The degree of retention, relearning, and extinction of the avoidance response was not modulated by the serial ablation procedure whether or not there was interoperation retraining experience. However, reversal learning, in which the previous warning signal became the safety signal and the previous safety signal became the new warning signal, was less impaired following serial ablations than following single-stage bilateral ablation. These results are contrasted with those from experiments with mammalian subjects.     

Unconditional stimulus intensity and cardiac conditioning in the goldfish (Carassius auratus)

Independent groups of small restrained goldfish were given pairings of an illumination increase CS and shock USs of different intensities. The relation between conditioned cardio-deceleration and US intensity was a simple monotonic one with an apparent asymptote between 1.3 and 2.2 V/cm. There was no sign of cardio-acceleration at any point in adaptation, conditioning, or extinction. Baseline heart rate was little affected by conditioning but post US rate decreases mirrored the conditioned decreases.     

Antiprotozoal activity of medicinal plants against Ichthyophthirius multifiliis in goldfish (Carassius auratus)

Ichthyophthiriasis is a widespread disease in aquaculture and causes mass mortalities of fish. The development of new antiprotozoal agents for the treatment of Ichthyophthirius multifiliis infections is of increasing interest. The aim of the present study was to investigate the efficacy of 30 medicinal plants against I. multifiliis. The results showed that the methanol extracts of Magnolia officinalis and Sophora alopecuroides displayed the highest antiprotozoal activity against theronts, with 4-h LC(50) values estimated to be 2.45 and 3.43?mg?L(-1), respectively. Concentrations of 2.5, 5.0, 10.0, and 20.0?mg?L(-1) of M. officinalis extracts resulted in tomont mortality of 9.7, 43.7, 91.3, and 100?% at 20?h, respectively. From 40 to 320?mg?L(-1) of S. alopecuroides extracts, tomont mortality increased from 29.7 to 100?%. Antiprotozoal efficacy against settled tomonts (2 and 10?h) was also applied; the results indicated that encysted I. multifiliis tomonts were less susceptible to these plant extract treatments. In vivo experiments demonstrated that high concentrations of M. officinalis and S. alopecuroides extracts could kill tomonts, and M. officinalis significantly reduced its reproduction (P?相似文献   

Involvement of the telencephalon in spaced-trial avoidance learning in the goldfish (Carassius auratus)

Goldfish (Carassius auratus) received escape-avoidance training in a shuttle-response situation at a rate of a single trial per day. Widely spaced training evaluates the ability of a discriminative stimulus to control an avoidance response in the absence of stimulus carry-over effects from prior recent trials. In Experiment 1, master goldfish exhibited significantly faster avoidance learning than yoked controls. The results suggest that the shuttle response was instrumentally acquired. Experiment 2 demonstrated a significant deficit in the acquisition of avoidance behavior following ablation of the telencephalon. The implications of spaced-trial, telencephalon-dependent avoidance learning, as demonstrated in these experiments for the first time, are discussed in the context of comparative research on instrumental learning in goldfish. These results provide further support for the hypothesis that the fish telencephalon contains an emotional system that is critical for fear conditioning.     

The role of telencephalic NMDA receptors in avoidance learning in goldfish (Carassius auratus)

Studies with goldfish (Carassius auratus) have suggested that N-methyl-D-aspartate (NMDA) receptors are concentrated most densely in the telencephalon, a simple structure homologous to the limbic structure of higher vertebrates. The present study investigated the amnestic effects of microinjections of the NMDA receptor antagonist D(-)-2-amino-5-phosphonopentanoic acid (D-AP5) to the goldfish telencephalon on avoidance conditioning. Results showed that microinjections of D-AP5 before training impaired avoidance learning at doses that did not impair performance processes. High-performance liquid chromatography measurements showed that D-AP5 was detected only in the telencephalon following microinjections. Thus, D-AP5 impaired avoidance learning through its interaction with telencephalic NMDA receptors in goldfish. Furthermore, microinjections of D-AP5 to the goldfish telencephalon immediately following training did not impair memory consolidation of avoidance conditioning.     

Respiratory responses to hypoxia or hypercapnia in goldfish (Carassius auratus) experiencing gill remodelling

The presence of an interlamellar cell mass (ILCM) on the gills of goldfish significantly decreases the functional lamellar surface area and increases the diffusion distance for gas transfer and thus may impose a serious challenge for the transfer of respiratory gases (O₂ and CO₂). Here we tested the hypothesis that the presence of the ILCM in goldfish acclimated to 7 °C impedes the uptake of O2 and excretion of CO₂. While Pa_O2$\text{P}{\text{a}}_{{\text{O}}_2}$ remained unaltered, the baseline values of Pa_CO2$\text{P}{\text{a}}_{\text{C}{\text{O}}_2}$ were significantly higher in goldfish at 7 °C with ILCM present (5.55 ± 0.54 mmHg; mean ± SEM) than in goldfish at 25 °C without the ILCM (3.98 ± 0.18 mmHg). Carbonic anhydrase (CA) injections relieved the apparent diffusion limitation imposed by the presence of the ILCM on CO₂ excretion (Pw_CO2$\text{P}{\text{w}}_{\text{C}{\text{O}}_2}$ levels dropped to 3.07 ± 0.32 mmHg). Interestingly, the exposure of fish to acute hypoxia evoked similar changes in Pa_O2$\text{P}{\text{a}}_{{\text{O}}_2}$ at the two acclimation temperatures. Ethanol (EtOH) exposure was also used as a tool to further investigate the potential effects of the ILCM on branchial solute transfer. The results showed that the ILCM does not impede EtOH uptake in 7 °C goldfish. Overall, the results of this study demonstrate that the remodelling of the goldfish gill associated with acclimation to 7 °C water, while increasing Pa_CO2$\text{P}{\text{a}}_{\text{C}{\text{O}}_2}$, has minimal impact on branchial O2 transfer.     

Transfer of taste preference from trained goldfish (Carassius auratus) into untrained recipients

Summary In a shock-free procedure, goldfish were trained to acquire a preference for quinine or acetic acid for which they have an innate repulsion. Recipients of brain extracts taken from trained donors showed a positive reaction to the previously dislike taste quality. The change in reaction was observed between the second and the seventh day after injection. It was not exhibited by recipients of brain extracts prepared from untrained donors.Supported by Deutsche Forschungsgemeinschaft (Sonderforschungsbereich 33).     

Effects of gold thioglucose on food intake,growth and forebrain histology in goldfish,Carassius auratus

The effects of gold thioglucose (GTG) injected intraperitoneally or into the ventricles of the brain on food intake, body weight gain, and forebrain histology in the goldfish were investigated. GTG caused a dose-dependent decrease in food intake, and usually initially caused loss of body weight, or at least slowed the rate of weight gain for up to 4 weeks. Over a long term the tendency was for recovery of normophagia and recovery of the normal rate of body weight gain. No significant effects on plasma glucose concentrations or growth hormone concentrations were detected following GTG treatment. No lesions were observed in the ventromedial hypothalamus of goldfish following intraperitoneal or brain injection of GTG. A dose dependent hypertrophy of the ependyma of the forebrain was found following brain injection of GTG. However, ependymal hypertrophy was found in only about half of the fish injected intraperitoneally with GTG at a dosage causing hypophagia. There was disruption of the ependyma lining the lateral-dorsal aspect of the lateral recess of the third ventricle, and some hypertrophy of the adjacent nucleus recessus lateralis, following brain injection, but not intraperitoneal injection, of a dose of GTG effective in causing decreased weight gain and hypophagia. Since no consistent histological effects of GTG were observed, its site of action in causing decreased weight gain and hypophagia in the goldfish is unknown. Fish injected with gold chloride all died soon after injection. Gold thiomalate injection caused weight loss and slowed the rate of weight gain, similar to GTG. The mechanism by which GTG causes hypophagia and decreased growth in goldfish is probably not related to the specific uptake of glucose by some brain center.     

Central administration of melanin-concentrating hormone (MCH) suppresses food intake, but not locomotor activity, in the goldfish, Carassius auratus

Melanin-concentrating hormone (MCH) is a hypothalamo-pituitary peptide, which was first identified in the salmon pituitary as a hormone affecting body color. Recently, MCH has been implicated in the regulation of feeding behavior and energy homeostasis in mammals. Despite a growing body of knowledge concerning MCH in mammals, however, there is little information about the effect of MCH on appetite and behavior in fish. The aim of the present study was to investigate the action of MCH on feeding behavior and spontaneous locomotor activity in the goldfish. We administered synthetic MCH by intracerebroventricular (ICV) injection and examined its effect on food intake and locomotor activity using an automatic monitoring system. Both types of synthetic MCH we employed, which are of fish and human origin, were effective in stimulating aggregation of melanin granules in the melanophores of goldfish scales. Cumulative food intake was significantly decreased by ICV injection of both MCHs in a dose-dependent manner. ICV injection of fish MCH at the same doses as those used for examination of food intake induced no marked changes in locomotor activity during the observation period. These results suggest that MCH influences feeding behavior, but not spontaneous locomotor activity, in the goldfish, and may exert an anorexigenic action in the goldfish brain, unlike its orexigenic action in mammals.     

Transfer of control of avoidance behavior in normal and telencephalon ablated goldfish (Carassius auratus)

Three groups of goldfish (2 normal and 1 telencephalon ablated) were trained to avoid electric shock by crossing a barrier in a twoway shuttle box whenever a tone sounded. Then, while isolated in a distinct compartment, one normal and the ablated group received discriminative classical defense conditioning with two visual cues (CS+, CS?), while the other normal group received pseudoconditioning. Lastly, in the shuttle box, all fish had unreinforced test presentations of the visual CSs intermixed with avoidance retraining trials to the tone. The classical conditioned normal and ablated groups did not differ and both showed immediate, discriminative transfer of control of avoidance responding to the CS+ as they did to the tone, while for the pseudoconditioned normal fish the CSs did not control avoidance behavior. These results suggest that the telencephalon does not play a significant role in the integration and utilization of conditioned fear reactions with previously learned avoidance responses to generate appropriate behavior.     

Cardiac, ventilatory and behavioural arousal responses evoked by electrical brain stimulation in the goldfish (Carassius auratus)

Goldfish (Carassius auratus) were fitted with intracranial stainless steel microelectrodes for electrical evocation of behavioural arousal and its cardiac and ventilatory correlates. Behaviour was monitored on a videosystem and ECG electrodes and a buccal catheter were implanted to monitor physiological responses. Thresholds for responses were described in relation to the current spread likely to excite CNS tissue. Two types of responses were obtained. These were (A) cardiac and ventilatory responses alone, apparently due to stimulation of primary sensory pathways and (B) these responses and behavioural arousal responses which were elicited at higher thresholds. These latter, more complete expressions of arousal resulted from stimulation of the Dm/Dc region of the telencephalon, the dorsal diencephalon and the midbrain tegmentum. Response thresholds were higher and physiological response magnitudes lower in the midbrain tegmentum compared to the forebrain regions.     

Isolation and partial characterization of immunoglobulins of goldfish (Carassius auratus) and carp (Cyprinus carpio)

Two related species of teleost fishes, the goldfish (Carassius auratus) and the carp (Cyprinus carpio), responded to injection of protein antigens by producing antibodies which resembled the γM immunoglobulins of other vertebrates in size and polypeptide chain structure. No other immunoglobulin classes were observed in these fish. Since the ancestors of the teleosts diverged from those of the tetrapods over 300 million years ago, the present results are consistent with the hypothesis that light chains and μ-type heavy chains emerged early in vertebrate evolution.     

Screening of plant extracts for anthelmintic activity against Dactylogyrus intermedius (Monogenea) in goldfish (Carassius auratus)

With the aim of finding natural anthelmintic agents against Dactylogyrus intermedius (Monogenea) in goldfish (Carassius auratus), 26 plants were screened for antiparasitic properties using in vivo anthelmintic efficacy assay. The results showed that Caesalpinia sappan, Lysima chiachristinae, Cuscuta chinensis, Artemisia argyi, and Eupatorium fortunei were found to have 100 % anthelmintic efficacy at 125, 150, 225, 300, and 500 mg L^?1 after 48 h of exposure. Crude extract of the five plants were further partitioned with petroleum ether, chloroform, ethyl acetate, methanol, and water to obtain anthelmintically active fractions with various polarity. Among these fractions tested, the ethyl acetate extract of L. chiachristinae was found to be the most effective with a 50 % effective concentration (EC₅₀) value of 5.1 mg/L after 48 h of exposure. This was followed by ethyl acetate extract of C. chinensis (48 h-EC₅₀?=?8.5 mg L^?1), chloroform extracts of C. sappan (48 h-EC₅₀?=?15.6 mg L^?1), methanol extract of C. chinensis (48 h-EC₅₀?=?15.9 mg L^?1), and chloroform and petroleum ether extract of L. chiachristinae (EC₅₀ values of 17.2 and 21.1 mg/L, respectively), suggesting that these plants, as well as the active fractions, provide potential sources of botanic drugs for the control of D. intermedius in aquaculture.     

Functional characterization of apoptosis-associated speck-like protein (ASC) of the goldfish (Carassius auratus L.)

Quantitative expression analysis of goldfish ASC indicated the highest and lowest mRNA levels in spleen and muscle, respectively. The ASC was differentially expressed in normal goldfish tissues and different immune cell populations. The highest ASC mRNA levels were observed in the spleen and macrophages. We generated a recombinant form of the molecule (rgfASC) and an anti-ASC IgG antibody, and report that treatment of goldfish macrophages with nigericin, an inducer of inflammasome pathway, up-regulated the expression of ASC at both mRNA and protein levels. rgfASC aggregated to form multimers in cross-linking assays, and formed speck-like structures visualized by confocal microscopy. Co-immunoprecipitation assays showed that rgfASC interacted with caspase-1 and receptor-interacting serine/threonine kinase 2 (RIP2). The dual luciferase reporter assay showed that ASC over-expression did not cause the activation of NF-κB directly, but down-regulated RIP2 ability to activate NF-κB. Goldfish ASC was found to interact with both Nod-like receptor and inflammasome signaling pathway molecules, suggesting multifunctional roles for ASC in regulation of different NLR signaling pathways and eventual proinflammatory cytokine production by activated macrophages.     

Neuropeptide Y mediates ghrelin-induced feeding in the goldfish, Carassius auratus

Intracerebroventricular (ICV) and intraperitoneal (IP) administration of n-octanoic acid-modified ghrelin stimulates food intake in the goldfish. We examined the involvement of neuropeptide Y (NPY) in the orexigenic action of ghrelin using a NPY Y1-receptor antagonist, BIBP-3226. Food intake induced by ICV or IP injection of ghrelin was suppressed by ICV preinjection of BIBP-3226 for 1 h. We then examined whether ghrelin affects the expression of NPY mRNA in the goldfish brain using a real-time PCR method. ICV, but not IP, administration of ghrelin at a dose sufficient to stimulate food intake increased the expression of brain NPY mRNA obtained from 2 h after treatment. These results indicate that the orexigenic action of central ghrelin is mediated by the release of NPY in the brain with stimulating NPY synthesis, and that peripheral ghrelin also stimulates food intake via brain NPY pathway.     

Beta 2 microglobulin-like polypeptide of the goldfish, Carassius auratus

Antisera to human beta 2 microglobulin (beta 2M) detected a plasma membrane molecule on goldfish (Carassius auratus) cells in immunofluorescence. A goldfish molecule detected by radioimmunoassay (RIA) co-eluted with human beta 2M on gel filtration. By affinity chromatography on immobilized antibody to human beta 2M, a molecule was purified (from extracts of goldfish) that showed, on SDS-polyacrylamide gel electrophoresis, a mobility similar to that of human beta 2M (apparent Mr 12,800 +/- 500).     

Effects of lithium on visual perceptual thresholds in the goldfish (Carassius auratus).

Following treatment with lithium chloride, goldfish showed reduced sensitivity to novel visual stimulation, but with increasing intensity of stimulation the effects of lithium treatment were gradually overcome. The results are related to a possible effect of lithium on central stimulus analysing mechanisms.