L-histidine reduces inhibitory avoidance in Carassius auratus submitted to cerebellar ablation

The effect of post-training treatment with L-histidine (LH) on the memory consolidation of inhibitory avoidance was investigated in Carassius auratus submitted to cerebellar ablation. The inhibitory avoidance procedure included 3 days: one habituation day, one training day (5 trials, T1-T5) and one test day. On the training day, each fish was placed individually in a white compartment separated from a black compartment by a sliding door. When the fish crossed into the black compartment, a weight was dropped in front of it (aversive stimulus) and the time to cross was recorded. Saline or LH (100 mg/kg) was injected intraperitoneally 10 min after the trials. Data were log10 transformed and analyzed by ANOVA and the Student-Newman-Keuls test (P < 0.05). In T5, all groups [ablation/LH (N = 15; 189.60 ± 32.52), ablation/saline (N = 14; 204.29 ± 28.95), sham/LH (N = 14; 232.36 ± 28.15), and sham/saline (N = 15; 249.07 ± 25.82)] had similar latencies that were significantly higher than T1 latencies [ablation/LH (89.33 ± 20.41), ablation/saline (97.00 ± 25.16), sham/LH (73.86 ± 18.42), and sham/saline (56.71 ± 17.59)], suggesting acquisition of inhibitory avoidance. For the test, there was a significant reduction in latencies of ablation/LH (61.53 ± 17.70) and sham/saline (52.79 ± 25.37) groups compared to the ablation/saline (213.64 ± 29.57) and sham/LH (199.43 ± 24.48) groups, showing that cerebellum ablation facilitated retention of inhibitory avoidance and LH reversed the effect of ablation. The results support other evidence that LH impairs memory consolidation and/or reduces the interpretation of aversion value.

Chlorpheniramine facilitates inhibitory avoidance in teleosts submitted to telencephalic ablation

The present study investigated the involvement of H(1) histaminegic receptor on the acquisition of inhibitory avoidance in Carassius auratus submitted to telencephalic ablation. The fish were submitted to telencephalic ablation 5 days before the experiment. The inhibitory avoidance procedure included 1 day for habituation, 3 days for training composed of 3 trials each (1st day: T1, T2, T3; 2nd day: 2T1, 2T2, 2T3; 3rd day: 3T1, 3T2, 3T3) and 1 day for test. On training days, the fish were placed in a white compartment, after 30 s the door was opened. When the fish crossed to a black compartment, a weight was dropped (aversive stimuli). Immediately after the third trial, on training days, the fish received, intraperitoneally, one of the pharmacological treatments (saline (N = 20), 8 (N = 12) or 16 (N = 13) µg/g chlorpheniramine, CPA). On the test day, the time to cross to the black compartment was determined. The latency of the saline group increased significantly only on the 3rd trial of the 2nd training day (mean ± SEM, T1 (50.40 ± 11.69), 2T3 (226.05 ± 25.01); ANOVA: P = 0.0249, Dunn test: P < 0.05). The group that received 8 µg/g CPA showed increased latencies from the 2nd training day until the test day (T1 (53.08 ± 17.17), 2T2 (197.75 ± 35.02), test (220.08 ± 30.98); ANOVA: P = 0.0022, Dunn test: P < 0.05)). These results indicate that CPA had a facilitating effect on memory. We suggest that the fish submitted to telencephalic ablation were able to learn due to the local circuits of the mesencephalon and/or diencephalon and that CPA interferes in these circuits, probably due an anxiolytic-like effect.

Initial sexual maturity and fecundity of the goldfish Carassius auratus (Perciformes: Cyprynidae) under semi-controlled conditions

We studied the time of initial sexual maturity and the fecundity of the goldfish Carassius auratus under semi-controlled conditions. During the study the water temperature fluctuated from 21 to 30 degrees C, the pH between 7 and 8, and the dissolved oxygen between 5.5 and 7 ppm. Sixty days old juvenile fish received prophylactic treatments of brackish water (15 per thousand) and methylene blue baths (1%), and they were fed with live Daphnia magna. The initial sexual maturity occurred between 225 and 233 days of captivity. Mean absolute fecundity was 2,347 (+/- 302.2 SD) ova per gonad, and mean relative fecundity was 63.44 eggs/g fish weight. Gonadosomatic index was between 7.5 and 9.0. Our data will allow ornamental fish producers to calculate the time of initial maturity and fecundity for this species.

Estudiamos el tiempo inicial de madurez sexual y la fecundidad del pez dorado Carassius auratus en condiciones semi-controladas. Durante el estudio la temperatura del agua varió de 21 a 30 oC, el pH entre 7 y 8, y el oxígeno disuelto entre 5.5 y 7 ppm. Jóvenes de 60 días de edad recibieron tratamiento profiláctico con agua salobre (15 ‰), y baños de azul de metileno (1 %). Se les alimentó con Daphnia magna. La madurez sexual inicial fue tras 225 a 233 días en cautiverio. La fecundidad absoluta media fue de 2 347 (±302.2 DS) óvulos por gónada y la fecundidad relativa fue de 63.44 óvulos/g del peso del pez. El índice gonadosomático se calculó entre 7.5 and 9.0.

Reinforcing properties of the substance P C-fragment analog DiMe-C7 in Carassius auratus

The aim of the present study was to investigate whether two substance P (SP) fragments have reinforcing effects in Carassius auratus when the fish were tested in a place-preference experimental model. Fish were placed in a 3-compartment box in which one compartment gives access to two others that are not connected. The time spent in each compartment was recorded for 10 min in order to determine which one was preferred. Twenty-four hours later the fish were given one of the following ip treatments: 1) group VEH (N = 12), injected with teleost saline, 2) group DiMe-C7 (N = 12), injected with 33 mug/kg DiMe-C7, and 3) group SP1-7 (N = 12), injected with 167 mug/kg SP1-7. Immediately after treatment the fish were kept for 30 min in the compartment that was the least preferred on the day before and this procedure was repeated for 3 days. On the fifth day the fish were retested for 10 min to determine the time spent in each compartment. Two-way analysis of variance with treatments and testing as factors indicated a main effect (P<0.0025) as well as a testing effect (P<0.009). The post-hoc Scheffé multiple comparison test indicated that only the DiMe-C7 group presented an increase in the time spent in the paired compartment after treatment. We suggest that the C-tenninal fragment of SP has reinforcing effects in Carassius auratus.