The Effect of Chlorpromazine and Thioridazine on the Exploration of a Y‐maze by Rats

Abstract

When a rodent is put into a situation with which it is unfamiliar, exploratory behaviour is elicited and the animal investigates the surroundings. In exploration, all the animal's sense organs are used to receive stimuli from the unfamiliar area and generally it moves through the area to increase the range of available stimuli. Many workers have used this movement as a measure of exploratory behaviour in the animal, and in particular Steinberg, Rushton & Tinson (1961), , Rushton, Steinberg & Tinson (1963) and Marriott & Spencer (1965) have studied movement in a Y-maze by rats and the way in which it is affected by various drugs.As a result of some differences found in the effects of chlorpromazine and thioridazine on the behaviour of mice and cats, which remained more active under thioridazine than under chlorpromazine a comparison was made between the effects of these two drugs on the exploration of a Y-maze by rats. Marriott & Spencer (1965) had found a decrease in the number of entries made into each arm of the maze when doses of chlorpromazine of 1 mg/kg, 4 mg/kg and 8 mg/kg were used. A similar procedure was followed as described by these workers. METHODSMale albino rats, supplied from Tucks, were used. They weighed between 80 g and 112 g and were housed in groups of 4 animals to a cage for 3 or 4 days before the experiments started. One day was allowed for conditioning to handling and injection. On this day they were taken to the laboratory and weighed and marked, and 3 hr later they were injected with saline and returned to their cages. After another 2 hr they were returned to the animal house. On the following day, the animals were taken to the laboratory and weighed 2-3 hr before they were injected with the drug. Groups of 8 animals were used at each dose level. In each experiment, one group was injected with saline and two groups were given one of the phenothiazines. The chlorpromazine and thioridazine were used as hydrochlorides dissolved in saline. The thioridazine turned blue on exposure to light and was kept out of the light when possible.The rats were injected subcutaneously into the neck 35 min before they were put into the Y-maze. The maze was made of three-ply wood varnished inside. It consisted of three arms 15 in. long and 4 in. wide which fitted on to a central triangle. It stood on the floor and was lit by a 200 watt lamp in the ceiling 2 m above it. The animals were put into one arm of the maze and watched for 5 min. During this time the number of entries into each arm, the number of rears and the number of times washing started were recorded. Defaecations were also counted. The rats were returned to their own cages after each trial and the cages were returned to the animal room each

Effects of Psychotropic Agents on the Exploratory Behavior of Rats in a Y-Shaped Box

“…Steinberg et al (1) showed that the naive rats explored relatively little at the first trial, but the number of entries to the arms of the box gradually increased in the successive trials. On the other hand, the gradual decrease in the number of entries caused by the repetition of the regular trials was reported by Mar riott and Spencer (4) and Schillito (7). In the present experiments the locomotion and rearing frequencies were relatively stable from the first to sixth trial in the Wistar strain rats and from second to sixth trial in the Sprague-Dawley strain rats.…”

A method for investigating the effects of drugs on the exploratory behaviour of mice

“…This can be seen when a mouse or rat is put in the same situation on two successive days, or even with some longer time interval between trials. Normal rats behave differently on two successive trials in a Y-maze as they move much less on the second trial (Shillito, 1967). Rushton, Steinberg & Tinson (1963) and Rushton, Steinberg & Tomkiewicz (1968) have found more complicated changes in behaviour which they attribute to an interaction between maze experience and drugs.…”

“…This movement has been used as a basis for measuring the effects of drugs on " exploratory " behaviour, a category of behaviour which gives the animal information about its environment. The effects of drugs on the movement of rats in a Y-maze were first studied by Rushton, Steinberg & Tinson (1961) and have also been used by Marriott & Spencer (1965), Shillito (1967) and others. Changes in the behaviour of mice as a result of drug treatment on a square board with regularly spaced holes in it have been studied by Boissier & Simon (1964) and Joyce, Porsolt, Steinberg & Summerfield (1968).…”

The Influence Of Kolanut (Cola Nitida) On Exploratory Behaviour In Rats

“…This response is indicative of retention and transfer of some experience from the first day. Shillito (1967) suggests that the decrease in movement observed on the second day can be taken to demonstrate that learning has taken place. The rats given the extract did not show significant habituation.…”

“…The other end of the arm at the centre was open to allow for movement from one arm into another. The three arms were made as similar as possible to prevent preference on the part of the animal when introduced into the maze (Shillito, 1967).…”