The ultrasonic postejaculatory vocalization and the postejaculatory refractory period of the male rat.

After ejaculation, the male rat emits an ultrasonic (22-kHz.) vocalization. This sound is produced repeatedly until about three fourths of the postejaculatory interval has elapsed. In this study, the occurrence of the vocalization was described, and physiological and behavioral evidence was presented that the postejaculatory vocalization reflects an inhibitory state that underlies the postejaculatory refractory period. The vocalization period was characterized by a predominance of slow-wave, spindling, sleep-like electroencephalographic activity. Electrical shock was able to stimulate mating responses only after the cessation of the vocalization period. It was concluded that an absolute refractory period of the postejaculatory interval lasts until the end of the vocalization period and that the time from the termination of the vocalization until the resumption of mating is a relative refractory period.     

Relation between 22-kHz ultrasonic signals and sociosexual behavior in rats

The copulatory performance of male rats, tested in a large seminaturalistic environment, was assessed to determine the relation between 22-kHz ultrasonic vocalizations and a range of sociosexual behaviors. The male rats were tested until sexual exhaustion. Such ultrasonic signals were shown to occur in a wider range of sociosexual circumstances than previously reported; for example, the calls occcurred in particular social circumstances during the preejaculatory period as well as during the postejaculatory interval. There was no consistent evidence that the emission of this call during the postejaculatory period consistently functions to keep the female away from the male. The nature and occurrence of postejaculatory ultrasonic signals showed increasing variability in successive ejaculatory series. The results of this and previous studies are interpreted within a semiotic theory of communication. The 22-kHz call is described as a message that makes available the information that the sender is in a socially depressed and withdrawn state.     

Effects of medial preoptic-anterior hypothalamic lesions on development of sociosexual behavior in dogs

Bilateral medial preoptic-anterior hypothalamic lesions in adult male dogs eliminate or impair copulatory behavior and reduce urine-marking responses but do not affect aggressive behavior. The present study examined the emergence of the adult forms of these same male sociosexual behavioral patterns when the lesions are made prior to puberty. The subjects were allowed to interact with male peers during development. Animals with lesions had reduced frequence of juvenile mounting and an almost total absence of male copulatory activity in adulthood. Urine-marking and aggressive behavior in the juvenile and adult periods were not affected by the lesions. The findings reveal a sparing of function with regard to urine-marking but not sexual behavior.     

Neocortex and feeding behavior in the rat.

Consummatory behavior and weight-regulation capacity were measured in 12 normal rats and in 43 rats that survived complete (C), sequential unilateral (U), anterolateral (A), or posterior (P) neocortical ablations. Groups C and A displayed aphagia and adipsia followed by a sequence of recovery stages gualitatively identical to, but shorter than, recovery typically seen following lateral hypothalamic lesions. After recovery, Group C displayed long-term effects of finickiness and pradial drinking. These effects as well as a measure of recovery of body-weight-regulation capacity were significantly intercorrelated with lesion size, and body-weight set point remained significantly lower than normal. Group U was relatively unaffected by the first unilateral ablation and showed, relative the second ablation but displayed the long-term effects. Group P, though significantly affected by the lesion, did not display the pattern or intensity of effects described for the other bilaterally ablated groups.     

Decline of maternal behavior in the virgin and lactating rat.

Sensitized virgins and postpartum lactating mothers, both exhibiting maternal behavior, were given donor litters that increased in age by 1 day, for 28 days, starting at the onset of maternal behavior. Each day females were tested for maternal behavior with pups 4-8 days old: Maternal care (i.e., nursing/crouching, retrieving, nest building and licking) and maternal withdrawal, rejection, and prevention of nursing were recorded. After the ninth day, females were also tested with the progressively older pups from 10 to 28 days of age with which they were living. Virgins and lactating mothers showed generally similar patterns of maternal care although some differences were found, and they declined in maternal behavior toward the older pups in a similar manner. Maternal behavior did not decline in tests with younger pups. The results are interpreted as supporting the hypothesis that the decline as well as the maintenance of maternal behavior postpartum is nonhormonally mediated.     

Hysterectomy-induced maternal behavior during pregnancy in the rat.

Hysterectomies were performed between the 10th and 19th day of pregnancy, and females were tested with pups for the onset of maternal behavior starting 0,24, 48, or 72 hr after surgery. Pups remained with the females overnight, and testing was repeated daily with fresh pups until females exhibited maternal behavior. Latencies for the onset of maternal behavior were shorter after hysterectomy on the 10th and 16th days of pregnancy than in intact pregnant females at the same stages of pregnancy; latencies became shorter, the later the termination of pregnancy. When the ovaries were removed along with hysterectomy during pregnancy, short-latency maternal behavior no longer was exhibited. Pregnant females were tested during the last 40 hr of pregnancy: nest building began at 34 hr prepartum and retrieving at 28 hr prepartum. The effect of hysterectomy during pregnancy on ovarian secretion of estrogen and progesterone is reviewed, and it is concluded that the rise in estrogen secretion, which follows hysterectomy during pregnancy, is most likely the cause of the rapid onset of maternal behavior after hysterectomy. A similar proposal is made for the prepartum onset of maternal behavior in intact pregnant females.     

Medial preoptic area and onset of maternal behavior in the rat.

The present series of experiments examined whether the medial preoptic area (MPOA) is involved in the onset of maternal behavior in the rat. Previously, the MPOA had been shown to be important in the maintenance of maternal behavior in the lactating rat. The first experiment investigated whether estradiol benzoate (EB) acts on the MPOA to facilitate the onset of maternal behavior in the 16-day pregnant, hysterectomized, and ovariectomized female rat. Such rats when given EB implants in the MPOA had significantly shorter latencies for the onset of maternal behavior than had females implanted with cholesterol in the MPOA or with EB in the ventromedial hypothalamus, in mammillary bodies, or under the skin. A second experiment showed that estrogen-induced prolactin release was not involved in this facilitation. A third experiment indicated that MPOA lesions disrupt the onset of maternal behavior that is induced by pup stimulation in virgin females. It was concluded that the MPOA is involved not only in the maintenance of maternal behavior but in the hormonally mediated onset of maternal behavior and the onset of maternal behavior induced in virgin females by pup stimulation.     

Factors in the waning of muricide in the rat. II. Digging behavior

If each mouse killed by a rat is removed from the rat's home cage and replaced immediately by another, the decline in the rate of killing within the one-hour sessions is accompanied by an increase in digging in the woodchip bedding material. Deprivation of the opportunity to dig by removal of the bedding material results in a statistically significant increase in kill rate. Since no other behaviors monitored showed a similar increase with this manipulation, it appears that digging may be a mechanism important in the waning of muricide. Furthermore, digging may be, in some sense, a functional equivalent of killing.     

Acoustic startle reflexes in the rat during consummatory behavior.

Auditory startle reflexes were elicited in thirsty rats when they were drinking water or were between drinking boutsmthe reaction was greater during drinking, this enhancement developing over the first few seconds after drinking onset. The startle reaction was lowest immediately after the termination of drinking. Reflex enhancement was reduced when thirsty rats drank milk rather than the more preferred water. The reflex was smaller with increased water deprivation, but enhancement produced by drinking was apparent at all levels of deprivation studied, satiety to 4-days deprivation. The inhibitory effect of a preliminary stimulus was not affected by consummatory behavior. Attention is drawn to suggestive parallels between these behavioral effects and other consequences of consummatory activity, primarily having to do with electrophysiological events and arousal processes     

Stability of visceral behavior in the awake rat during rest.

Brady and colleagues have championed the importance of careful delineation and control of a subject's behavioral state. In this paper we develop the concept of visceral behavior from a physiological perspective. Sprague-Dawley rats were instrumented to record arterial blood pressure, renal sympathetic nerve activity, and respiration. The rats were restrained in a conical cloth sock. Rats that were well adapted to the sock restraint showed a regular respiratory pattern and consistent pressure recordings; they rested quietly in the sock and moved only occasionally to adjust their position. Fourier analysis of blood pressure and nerve activity showed a concentration of power below 1 Hz. The coherence between the two signals was strong (0.83 +/- 0.03) at 0.42 Hz. Conversely, during their initial adjustment to the sock restraint, the rats tended to show large fluctuations in blood pressure associated with episodic apneic breathing; 1 animal displayed this pattern of visceral behavior throughout most of the experiment. Despite this instability in pressure, the rats' overt behavior was stable: They rested quietly in the sock with only occasional position shifts. Spectral analysis and coherence computations showed large shifts in the distribution of power and frequency range over which arterial pressure and sympathetic activity were tightly coupled. These data are consistent with the view that an animal's circulatory adjustments, as well as adjustments in other aspects of its physiological state, constitute an important aspect of behavior, and that this behavior can influence the interpretation of biobehavioral data.     

Hippocampal and cortical activity during sexual behavior in the female rat.

Hippocampal and cortical activity were studied during sexual behavior in the female rat. Hippocampal theta appeared during her soliciting behavior. High-frequency theta accompanying the male's pursuit slowed when the male mounted the female and then increased in frequency during the brief continuation of lordosis following mounts without vaginal penetration. During prolonged lordosis after intromissions and ejaculations, slow theta continued. No changes in cortical frequencies were observed during mounts, intromissions, or ejaculations. During immobility (standing, sitting, and lying down) hippocampal activity became slow and irregular. High-amplitude hippocampal and, eventually, cortical spindles developed during immobility as sexual exhaustion was approached. Immobility and its accompanying electroencephalographic spindling are interpreted as indicative of a sexual satiety or inhibitory process.     

Self-stimulation and mating behavior in the male rat

Abstract.— A presumed relationship between selfstimulation of the brain and sexual behavior was studied in two experiments. In the first experiment the male rat was allowed self-stimulation during a period of 5 minutes and thereafter transferred to a mating cage with a female. No effects of the self-stimulation were recorded in the mating behavior. In the second experiment the male was allowed one intromission and thereafter presented with a lever for self-stimulation, still having access to the female. The sexual responses were completely inhibited, and selfstimulation at normal rate resumed. It was concluded that there is no necessary link between self-stimulation of the brain and sexual behavior.