Time-dependent bidirectional effects of chronic caffeine on functional recovery of the dorsal light reflex after hemilabyrinthectomy in the goldfish Carassius auratus.

Caffeine works through a variety of complex mechanisms to exert an often bidirectional set of functional and structural neurological changes in vertebrates. We investigated the effects of chronic caffeine exposure on functional recovery of the dorsal light reflex (DLR) in hemilabyrinthectomized common goldfish, Carassius auratus. In this lesion model, the unilateral removal of the vestibular organs results in a temporary loss of gravitationally modulated postural control which is quantifiable via the DLR. We compared the functional recovery over 24 days of post-surgery goldfish continuously held in a caffeine solution of 2.5mg/L (n=10), 5.0mg/L (n=10), 10.0mg/L (n=11), or 0.0mg/L control (n=9). Comparison to a sham surgery group (n=11) indicated statistically significant changes in the DLR of all hemilabyrinthectomized fish on day 1. The control group recovered over the study period and approached, but did not reach sham surgery DLR. Although the caffeine-treated fishes appeared to initiate some postural recovery within the first 2 weeks, beginning on day 10, all caffeine groups diverged from the control group with a deterioration of postural control. All three caffeine groups were significantly deficient in comparison with the control on days 10-24. These results suggest that caffeine exposure can at first be benign, but that high dosage or prolonged exposure hinders functional recovery.

Changes in motoric, exploratory and emotional behaviours and neuronal acetylcholine content and 5-HT turnover in histidine decarboxylase-KO mice.

Histamine has been implicated, inter alia, in mechanisms underlying arousal, exploratory behaviour and emotionality. Here, we investigated behavioural and neurochemical parameters related to these concepts, including open-field activity, rotarod performance and anxiety, as well as brain acetylcholine and 5-HT concentrations of mice deficient for the histidine decarboxylase (HDC) gene. These mice are unable to synthesize histamine from its precursor histidine. The HDC-knockout mice showed reduced exploratory activity in an open-field, but normal habituation to a novel environment. They behaved more anxious than the controls, as assessed by the height-fear task and the graded anxiety test, a modified elevated plus-maze. Furthermore, motor coordination on the rotarod was superior to controls. Biochemical assessments revealed that the HDC-knockout mice had higher acetylcholine concentrations and a significantly higher 5-HT turnover in the frontal cortex, but reduced acetylcholine levels in the neostriatum. These results are suggestive of important interactions between neuronal histamine and these site-specific neurotransmitters, which may be related to the behavioural changes found in the HDC-deficient animals.

ACTH4-10, substance P, and dizolcipine (MK-801) accelerate functional recovery after hemilabyrinthectomy in goldfish.

In this study, we evaluated the goldfish model of hemilabyrinthectomy for investigating potential recovery-promoting drugs. In this lesion model, the unilateral removal of the labyrinth induces a postural imbalance in response to light (Dorsal Light Reflex), from which the animals can recover over time. The behavioral effects of two neuropeptides were tested--namely, of substance P and ACTH4-10, both of which are known to promote functional recovery in several other lesion models. Furthermore, the effect of MK-801, an antagonist of the glutamatergic NMDA-receptor subtype, was tested because this substance has also been shown to exert a neuroprotective effect. After lesion of the right labyrinth, the animals (n = 12) were treated intraperitoneally daily either with vehicle (n = 12), substance P (n = 11), ACTH4-10 (n = 12), or MK-801 (n = 12). Another group (n = 11), which served as a non-lesion control, did not receive hemilabyrinthectomy or systemic injections. The lesion group, treated post-operatively with vehicle, did not recover from the postural deviation over the 24-d testing period. In contrast, all three test substances accelerated the functional recovery after unilateral labyrinthectomy. The decrease of the dorsal light reflex persisted even after cessation of drug treatment after 20 d. The results indicate that using the dorsal light reflex in the model of hemilabyrinthectomy in goldfish provides a useful approach to studying the ability of potential new neurotrophic or neuroprotective drugs to promote functional recovery.

Ultrastructural analysis of folliculogenesis in the ovary of the yellow spotted stingray, Urolophus jamaicensis.

The ovary of the yellow spotted ray, Urolophus jamaicensis, is embedded in the epigonal gland, a lymphomyeloid organ. The covering of the ovary is composed of a germinal epithelium that is cuboidal and dome-shaped with microvilli. Adjacent cells have elaborate intercellular folds that create dilated intercellular spaces. In previtellogenic follicles, the follicle cells are simple cuboidal and contain modest amounts of synthetic or transport organelles. As vitellogenesis proceeds, the epithelium becomes multilaminar. Follicle cells are columnar as yolk precursors are transported from the maternal circulation, through the follicle cell cytoplasm, to the oocyte. Large, round cells occur in the follicle wall that contain lipid-like substances. These cells decrease in size and number as folliculogenesis proceeds and eventually disappear prior to ovulation. Columnar follicular cells and the oocyte have cellular extensions that impinge upon the zona pellucida. Transosomes are follicle cell extensions that indent the oocyte membrane. Tips of transosmes become enclosed by a layer of oocyte plasmalemma. The tips of transosomes pinch off and become resident in the ooplasm. Dense staining material occurs on the inner surface of the transosome membrane derived from the follicle cell. In Other animals, this material has been described as ribosome-like. This study is the first to document the presence of transosomes in a group other than Aves or reptiles. Follicle cells are supported by an extremely thick basal lamina. Subjacent to the lamina is the vascularized theca with fibroblasts embedded in a collagenous network. There is no differentiation into definitive theca interna and externa. In vitellogenic eggs, extensive inward folding of the follicular epithelium occur thereby generating more surface area for the transport of yolk precursors to the oocyte. Atretic follicles are common.

Post-trial administration of H1 histamine receptor blocker improves appetitive reversal learning and memory in goldfish, Carassius auratus.

Based on the hypothesis that neuronal histamine exerts an inhibitory influence on learning and reinforcement, goldfish were tested for post-trial effects of the H1 receptor blocker chlorpheniramine (CPA) on learning the location of a food source in one of two compartments, one black the other white, with a feeder located in each compartment. Testing was carried out over 6 days. On the training day a food pellet was placed into the feeder of one of the compartments. After consumption of the food the fish were injected i.p. with either vehicle or CPA either immediately after training or 3 h later. Twenty-four-hours later, food was placed in the same compartment and the time to begin feeding was recorded. On the next day the location of the food pellet was reversed, and testing was continued for 4 days. On the first test day the time to begin feeding was significantly longer for the vehicle injected fish as compared with those injected with CPA. The vehicle group also took longer to begin feeding than the CPA group on the first reversal test day. The results of the 3-h delay groups indicated no significant differences between vehicle and drug for any experimental session. These results suggest that post-trial blockade of the H1 histamine receptor can affect appetitive learning in goldfish either by improving long-term memory consolidation and/or by the additive reinforcing effects of CPA (known from previous studies) on behavior.

Conditioned place-preference analysis in the goldfish with the H1 histamine antagonist chlorpheniramine.

The aim of this study was to investigate whether the histamine H1-receptor blocker, chlorpheniramine (CPA), has a reinforcing effect in goldfish. We used a place-preference procedure in an aquarium with two chambers colored black and white. On day 1, the animals were placed in the test chamber for 10 min for habituation. On day 2, they were placed in the start compartment for 30 s, the sliding doors were opened, and the time spent in each compartment was recorded over the 10 min to determine the natural compartment preference for each animal. On day 3, they were injected either with 0.1, 0.4, 1.0, or 4.0 mg/kg of CPA or only with vehicle and placed in the less preferred compartment for 25 min. On day 4, the animals were placed in the start compartment and the time spent in each compartment during the 10-min test period was recorded again. The groups treated with 1.0 and 4.0 mg/kg of CPA, spent significantly more time in the compartment in which they experienced the drug effect than the group treated with vehicle. On the other hand, the group treated with 0.4 mg/kg spent significantly less time in the drug-paired compartment. The results indicate a biphasic effect of CPA. Considering that there is evidence that low doses of CPA can also block H3-receptors, we suggest that in goldfish the histaminergic neural system has an inhibitory role in the reinforcing process.

Metal redistribution in largemouth bass (Micropterus salmoides) in response to restrainment stress and dietary cadmium: role of metallothionein and other metal-binding proteins.

1. Fish stressed by restrainment displayed elevated serum cortisol, copper and zinc levels; dietary cadmium had no effect. 2. Stress/dietary cadmium increased liver copper levels in a metal pool containing metallothionein and non-metallothionein proteins but decreased intestinal zinc bound as low molecular weight forms. 3. After restrainment, zinc losses occurred in dorsal skeletal muscle, ovary and spleen: copper decreased in intestine and pyloric caecum. 4. Dietary cadmium altered intestinal zinc distribution and raised hepatic Cu-binding protein levels but did not alter plasma zinc, copper or cortisol levels. 5. Alterations in zinc and copper concentrations during stress contrast with mammalian models.

Effects of the light-dark cycle and scheduled feeding on behavioral and reproductive rhythms of the cyprinodont fish, Medaka, Oryzias latipes.

Medaka were maintained on a 16:8 light-dark cycle and fed once daily on one of 5 different feeding schedules. The daily rhythm of agonistic behavior rapidly entrained to the scheduled feeding time and maintained this entrainment during a 3-day starvation period. In contrast the daily rhythms of egg laying and courtship stayed entrained to the L:D cycle regardless of the feeding schedule. Thus, temporal integration of this fish with its daily environment can involve multistimuli which concurrently and differentially entrain externally expressed circadian systems.

Feeding time differentially affects fattening and growth of channel catfish.

Channel catfish (Ictalurus punctatus) were held on a 12-h light, 12-h dark photoperiod (light onset 0600 h) and fed a nonpurified diet daily at either 0730 or 1600 h or a half ration at both of these times of day. The feeding time conducive to total growth (0730 h) differed from that conducive to fattening (1600 h). Fish fed a half ration at both times of day had body weights similar to those fed a single early meal but also had high abdominal fat weights similar to those fed a single late meal. Feeding schedule appears to be an important factor in determining the metabolic fate of nutrients.