Larsson (1956) and Beach and Jordan (1956) have described sexual exhaustion and recovery in the male rat. The present study was conducted to obtain comparable data for another species belonging to the same order. METHOD Selection and Maintenance of SubjectsThe 5s were 20 male hamsters (Cricetits aura/its) approximately 90 days old at the beginning of experimentation. They were born.and reared in the Yale laboratory. Males were selected on the basis of their performance in a preliminary mating test in which they were required to copulate and ejaculate within 15 min. from the time that they were placed with a receptive female. Throughout the experiment the males were housed in pairs in the experimental room in which the day-night cycle of illumination was artificially reversed. Purina lab chow and drinking water were constantly available, and fresh greens were added once each week.

nide-sensitive terminal respiratory pathway. The other, in which menadione or other electron acceptors can function, does not involve the cyanide-sensitive pathway, but rather a diaphorase type flavoprotein-catalyzed cyanide-insensitive reaction. l\10RTON 1\1.

No abstract

·AbstractSixty guinea-pigs were given 50 avoidance conditioning trials in a shuttle-box and then retested either 0, I, 24, 48, of 168 hr. later. Little improvement in performance was observed within sessions but animals retested at 48-and 168-hr. intersession intervals were substantially better than all others. ProblemIn a study of shuttle-box avoidance conditioning in guinea-pigs, the authors found that animals made few avoidance responses in 50 or even 150 trials and showed little or no improvement in performance over trials. If the Ss were given a second training session two days later, a striking improvement was noted. One S made only three avoidance responses in the first session of 50 trials (only 1 in the last 20 trials) but made 18 avoidance responses in a 20 trial session two days later. The present study was conducted to confirm these observations and to explore the improvement in performance as a function ofthe duration ofthe intersession interval. MetbodThe Ss were 60 experimentally naive, young, female gUinea-pigs ranging in weight from 320 gm to 515 gm at the start of the experiment. The apparatus was a two compartment shuttle-box 30 in long, 6 in high and 7 in wida. There was no partition between the two halves of the box. The top and front side of the box were made of Plexiglas, the back and ends were unpainted plywood. The floor of each compartment consisted of 30 metal rods set 1/2 in apart. The CS was from a Holtzer Cabot 24-v buzzer suspended 9 1/2 in above the center of the box and from one of two 25-w lights mounted 2 1/2 in above the Plexiglas top at the ends of the box. The light over the compartment occupied by S was made to flash at 1 cycle per sec. A scrambled shock source (GrasonStadler, Model E6070B) supplied 3 ma at 350 v, 60 cycles, A. C.The first training session was the same for all Ss. After a 5-min. habituation period in the apparatus, each S was presented with the CS alone until no reaction was made for three consecutive trials. After the Ss had become acclimatized to the CS, 50 delay conditioning trials with a 10-sec. CS-UCS interval and I-min. intertrial interval were given. Both CS and UCS were terminated when the S crossed the center line of the shuttle-box.The 60 Ss were randomly assigned to five experimental groups with 12 Ss in each group. Each group received a second training session of 25 trials after an interval of 0, I, 24, 48, or 168 hr. With the exception Ptychon., Sci., 1964, Jlol. 1. C. D. Webster and Ronald G. RabedeauQUEEN'S UN~IT~ CANADA of the 0 interval group, Ss were returned to their living cages for the appropriate interval between sessions. In order to equate handling, Ss in the 0 interval group were taken from the apparatus after the 50 trials of the first session and replaced 30 sec. later. ResultsThe results in terms of percentage avoidance responses in blocks of trials are shown in Fig. 1. Since an analysis of variance on total number of avoidance responses for different groups in the first session was not significant, the individual group curves ha...

According to Beach (1942), the male rat's tendency to initiate coitus is controlled by a central excitatory mechanism (CEM) which reacts to sexual stimuli when selectively sensitized by an appropriate hormone (androgen). At a threshold excitatory level, the CEM discharges into motor centers which mediate copulation. The CEM may become reactive to normally inadequate stimuli after their repeated association, during copulation, with adequate sexual stimuli. The level of excitement is assumed to increase more rapidly and to reach a higher point when more stimulation acts upon the CEM. Finally, Beach slates that the motor centers for copulation remain relatively unaffected by this type of experience.It follows from this analysis that experienced males should reach excitatory threshold sooner and therefore require less time to make the first sexual contact after the female has been introduced. Moreover, in a time-limited test, a greater percentage of experienced than inexperienced males should become sufficiently aroused to achieve coitus. Other measures of sexual performance which are presumably controlled by motor centers, that is, the frequency and spacing of mounts, intromissions, and ejaculations, should be about the same for experienced and naive 5s which copulate at all.Before one would expect to observe the predicted differences, 5s must be of sufliciently low arousability at the time of testing for improvement to be measured. It is obvious that males which always copulate cannot improve in terms of percentage copulating. Also, males which initiate coitus within 10 or 15 sec. (the usual average) are not likely to show any great decrease in latency. Clearly, then, the most direct procedure of pairing