Thirty-six male albino rats of Wistar strain were selected for the study. The rats were of the same age group weighing 150–170 g. All the animals were maintained under standard laboratory conditions. Food andwater were available to all the animals ad libitum. About 1 week before commencement of the experiment, all the rats were tested for auditory sensation by observing the behavioral response to sound as described by Dickens (1973). The rats were randomly divided into six equal groups viz.