Y-maze tests

Striped bass, Morone saxatilis, juveniles develop in estuaries, notably Hudson River and Chesapeake Bay. Juveniles school during the day but disperse and feed at night. Schools provide the advantages of improved prey location, predator avoidance, and swimming hydrodynamics. How are the fish attracted to each other In Y-maze tests in the laboratory, juveniles are attracted to both... 

After injection of 1.85 g sample to the cerebral ventricle on each of three consecutive days, passive avoidance testing on days 1 and 2 and Y-maze testing on days 3 and 4 were conducted. Learning and memory-retention ability of the mice were performed according to the method of Song (1), while spontaneous alternation behavior of mice in a Y-maze test was performed according to the method of Yamada (2). 

Table 6, Y-maze tests of pheromone trail preference of members of the... 

Fig. 23.1 Results of the odor preference test in a Y-maze (A). Female mice carrying lesions in either the MOE (B) or VNO (C) were given a choice between volatile odors derived from an intact or a gonadectomized male...

A four-choice star maze, similar to that used by Kubie and Halpern (1978, 1979), was used as a two-choice Y maze for training the snakes. Snakes were trained to follow earthworm extract trails (IX = 6 gm earthworm per 20 ml dH20) in the apparatus until their performance exceeded chance behavior. (See Kubie and Halpern 1978 for details). At the termination of testing, snakes were videotaped during trailing at each earthworm concentration (IX, 1/9X, 1/8IX, Dry). Trials were repeated until a minimum of one minute of good, analyzable film had been obtained at each concentration. This usually involved one to three trials. For filming of animals from the side, a clear plastic maze of similar dimensions was used. 

Simple learning tests are, for instance, habituation to a tone, passive avoidance, simple tests of operant learning, simple maze tests (e.g. T or Y... 

Ranje C, Ungerstedt U (1977b) Lack of acquisition in dopamine denervated animals tested in an underwater Y-maze. Brain Res 754 95-111. 

To test their ability to discriminate individuals, male and female salamanders (in the US several species of the genus Plethodon) are given a choice of odors in a Y-maze. The odors tested can be male vs. female mate vs. strange individual of opposite sex individuals from different populations or closely related species (Dawley 1985). 

Delayed alternation is another possible training protocol for the T/Y-maze, in which animals are rewarded for choosing any goal box in trial one. They are then returned to the start box and released after an inter-trial interval. In trial two, they have to enter the arm not visited in trial one (non-match) and are rewarded. Typically, animals acquire a criterion of 80% correct responses after a short training period. When tested in the presence of A THC, there was a significant drop in performance coupled with a reduction in monoamine turnover in their prefrontal cortex (Jentsch et al. 1997). Animals treated with a similar dose (5 mg/kg) A THC, however, were not impaired in brightness discrimination (Jentsch et al. 1996) or visual discrimination of forms procedures (Mishima et al. 2001) administered in the same apparatus. 

Using a series of Y-maze olfiictoiy choice tests, we found that male red-spotted newts show a pheromonal repelling response and that the occurrence of the repelling response depends on the number of males present, on male-female interactions, and on female fecundity. The purpose of the work presented here is to describe and elaborate on the main findings that we have reported in previous studies (Experiment I-IV, Park and Propper, 2001 Experiment V-VI, Park et al., submitted). 

The two arms of the maze were continuously infused with aged t water at a flow rate of 30 ml/min from a reservoir containing 500 ml aged tap water. At this flow rate, water flow from the two arms remained separate to the drain at the end of the Y-maze nevertheless, test males could sample the water from both arms while behind the perforated starting gate. After each trial, mazes were washed using aged tap water. All experiments were conducted between 1000 and 1500 hr. 

We first verified that males have no preference when exposed to chemical cues from two same-sized females. An average, sexually-mature adult female newt has a mass of approximately 3 g. We used matched pairs of females that differed by less than 0.05 g in mass, placing one into each side arm of Y-maze, When subject males were allowed to choose between two same-size females, no preference was observed (Table 1, I one-tailed binomial test, P = 0.37). 

To determine whether a pheromonal repelling response occurs, we first placed one of two same-sized females into each arm of the Y-maze, and then added three males to one side to mimic a state of high male-male competition. In this experiment, the stimulus males and female were allowed to interact for 5 min in the side arm before each test begins. We found that subjects strongly preferred the arm containing a single female compared with that containing a female plus three males (Table 1, II one-tailed binomial test, P = 0.017). 

To determine whether chemical cues from three males alone are sufficient to repel conspecific males, we placed three males in one arm of the Y-maze and left the other arm empty. Subject males were then allowed to choose between the two arms. Subjects significantly preferred the arm containing three males to the arm containing nothing but plain water (Table 1, III one-tailed binomial test, P = 0.003). 

Table 1. Results of the Y-maze olfactory choice tests.

To determine whether female fecundity affects male choice, we determined whether or not subject males display a preference when presented with large and small females. We placed one large (3.75 0.57 g, n = 5) and one small (2.67 0.18 g, n = 5) female into each arm of Y-maze and allowed subject males to choose between them. Males showed a strong preference for the side containing the large female (Table 1, V one-tailed binomial test, P < 0.001). 

In the test phase (30 min to 7 days after fighting), the behavior of subjects was observed and recorded in a Y-maze. First, males were placed in a clean Y maze with no stimuli present and their behavior was recorded during a 3-min trial. At the end of this trial males were confined in the start box of the Y-maze and the fan that drew air through the maze was turned off for about 40 seconds while we placed a stimulus male into a compartment at the end of one arm of the Y. The fan was turned on and 20 sec later the subject was allowed to explore the Y-maze again for 3 min. We recorded time spent in various parts of the maze, latency to reach the ends of each arm of the maze, and overall activity (Lai and Johnston, 2002). 

Characteristic results are shown in Figure 2. One day after the interaction phase, males that lost fights spent more time in the base of the Y-maze, near the start box, than in either of the arms of the Y and they spent very little time near the male that had beaten them in the series of three encounters. In contrast, males that did not fight or those that were tested with an unfamiliar winner spent less time in the base of the Y and much more time near the stimulus male. Males that lost also took much longer to approach the end of the Y containing the familiar winner than the clean arm of the maze. Similarly, the latency to approach a stimulus male was much greater for males tested with a familiar winner versus those tested with an unfamiliar winner. Similar results were found when we tested males 30 min, 1 day, 3 days or 7 days after the three brief encounters (Lai and Johnston, 2002). 

Figure 2. The behavior of male hamsters in a Y-maze subjects had either fought and lost and were tested in a Y-maze or were exposed to an arena and were tested in a Y maze. Males that fought and lost (fight side) spent most of their time in the start box (top right) and took a long time to approach the familiar winner (bottom right). Males that were just exposed to a clean arena spent most time near the unfiuniliar winner (top left) and approached this male more quickly than the clean arm of the Y (bottom left). ( - p < O.OS Lai and Johnston, 2002)...

---