Ultradian rhythms in waking behavior of rhesus monkeys

The behavior of seven individually housed adult male rhesus monkeys was recorded by time-lapse video, 10 hr per day, for up to 5 days. Recordings were analyzed in 50 sec intervals for the presence or absence of 5 behavior, viz., ingestion, locomotion, exploration, self-grooming, and resting. Analyses were based on the number of 50 sec intervals per 5 min epoch in which each of these behaviors occurred. Variance spectra were computed on each behavior for each animal, and the significance of a prospectively predicted behavioral cyclicity in the frequency band of 12–18 cycles/day was explored with t tests for the group of monkeys. All 5 behaviors exhibited a statistically significant spectral peak as predicted. Significant cross-spectral relationships were found reflecting temporal relationships between ingestion, locomotion, exploration, and resting. The first 3 were in phase with one another and out-of-phase (reciprocal) with resting. Locomotion tended to precede exploration, and exploration to precede ingestion. These results suggest that the 12–24 cycles/day orality rhythm described earlier in monkeys is not discrete, but is one component of a more general 12–18 cycles/day behavioral cycle involving locomotion, exploration, and rest as well. Self-grooming, while perhaps cyclic, was not significantly related to the orality-locomotion-exploration complex.     

Ultradian rhythms in the mobility and behavior of rhesus monkeys

Summary The presence of ultradian rhythms in the mobility and behavior of rhesus monkeys was explored in eleven animals equipped with mobility FM transmitters and placed alone or in pairs in a laboratory cage situated in a sound proof, temperature controlled room, with food and water ad libitum. After an habituation period of 3 to 7 days, telemetric recordings of the mobility of the animals showed ultradian rhythms with a periodicity of 70 min during the daily 12-h light period. During the corresponding 12-h dark period, there were two dominant cycles of 103–144 min and 48 min respectively. Restriction of food and water to 1h/day did not change the duration of these cycles, and the presence of random noise also had little effect. Spontaneous behavior occurred in regular sequences within each cycle. Social relationships were found to affect rhythmicity of behavior, since pairs of monkeys synchronized their cycles. The lever press response recorded during auto-shaping showed the same rhythmicity found in mobility, demonstrating the influence of ultradian rhythms on learned behavior.     

Ultradian rhythms of solitary and social behavior in rhesus monkeys

Day-long observations were made on the social and nonsocial behaviors of five subadult to adult male monkeys. Social interaction between pairs of monkeys was found to occur as a cyclic process. In three of four pairs, the lengths of these cycles occurred as multiples of 45 min. Four nonsocial behaviors — ingestion, self-grooming, exploration and locomotion — were found to occur as cyclic processes when the monkeys were in either a social or a solitary setting. The lengths of these cycles again occurred as multiples of 45 min and in all four social pairings exploratory cycles of individual monkeys appeared to precede and be closely in phase with social interaction cycles.     

Sexual behavior in long-term vasectomized male rhesus monkeys.

It has been suggested that in man vasectomy may lead to problems of psychosexual adjustment such as impotency because of castration anxiety or other superstitions often associated with sexual behavior. An increase in sexual promiscuity has also been attributed to vasectomy and has been explained as a loss of fear of impregnating women companions. In monkeys, any alterations in sexual behavior after vasectomy probably are the result, not of cultural factors but of anatomical or immunologic changes resulting from the operation. The sexual behavior of male rhesus monkeys vasectomized 5 years earlier did not differ from that of sham-vasectomized controls. There was, however, a significant difference in the mean latencies to first mount and first intromission; vasectomized males had shorter latencies. In another set of studies, there were no siginificant differences between males vasectomized 12 years earlier (mean) and nonvasectomized controls. We found no association between the presence or absence of antisperm antibodies in the vasectomized males and their levels of sexual performance.     

Social behavior of juvenile rhesus monkeys after amygdalectomy in infancy

Six $\text{3}\text{1}\text{2}$-yr-old rhesus monkeys that had sustained a bilateral amygdalectomy in infancy were paired with 6 intact age-mates, and behaviors were observed immediately and after a 24-hr interval. Amygdaloid animals were submissive to controls, and were hyperactive during all tests, changing rapidly from one behavior to another. Earlier studies with these infant-operated monkeys showed that an abnormal fear of intact age-mates first appeared during the second 6 mo of life. The amygdaloid animals had been hyperactive when by themselves as early as 6 mo of age, but there was no evidence of hyperactivity in social situations during earlier tests. The present paper presents the histology for these infant-operated monkeys, and suggests that behavioral deficits resulting from amygdalectomy in infancy increase in severity with advancing maturation. The aberrations observed by $\text{3}\text{1}\text{2}$ yr are similar to those observed after amygdalectomy in mature animals.     

Self-injurious behavior in male rhesus macaques does not reflect externally directed aggression

Self-injurious behaviors (SIB), such as self-biting and self-wounding, have been observed in a small percentage of captive nonhuman primates. Because rhesus monkeys that exhibit SIB also tend to be more aggressive, it was hypothesized that SIB is related to externally directed aggression and is associated with contexts in which physical contact between participants is prevented. The purpose of this study was to test the hypothesized relationship between SIB and outward aggression. Subjects were first presented with videotapes of conspecifics, scenery and a blank screen, and their behavior was recorded. Levels of salivary cortisol, an indicator of stress, were also measured before and after presentation of the videos. Although aggression increased when subjects viewed tapes containing conspecifics, neither cortisol levels nor self-biting behavior varied as a function of tape content. The subjects were then placed in two additional test situations: an empty room and the same room containing an unfamiliar conspecific. Aggression was significantly higher in the stranger condition compared to the empty room condition. The two situations yielded parallel increases in cortisol, suggesting that being alone was just as stressful as being paired with an unfamiliar conspecific. Self-biting rates were also similar in these two conditions. Thus, contrary to our prediction, increases in aggression did not correlate with increases in SIB. These results suggest that under similarly stressful conditions, SIB and externally directed aggression are unrelated.     

Age differences in copulatory behavior and serum 17β-estradiol in female rhesus monkeys

Young, sexually mature female rhesus monkeys housed in outdoor groups have been found to exhibit significantly longer mating periods associated with first conception compared with the duration of the annual mating period exhibited by older, multiparous females. An analysis of the sexual behavior and corresponding serum concentrations of 17β-estradiol (E2) and progesterone (P) in two age groups of rhesus females revealed that young females copulated on significantly more days prior to the E2, ovulatory peak than did older females. Serum concentrations of E2 were significantly higher from ?30 to Day ?10 prior to the E2 peak (Day 0) in young females. Estradiol concentrations were similar for both age groups during the remaining follicular and periovulatory period. No age differences in serum P were observed between the two groups. Serum E2 levels associated with the onset of mating were similar in the two age groups with levels rising from 73.5±4.0 pg/ml prior to mating to 97.2±4.6 pg/ml. Thus the hormonal profile associated with the onset of mating is similar for both age groups, and the earlier occurrence of mating behavior prior to ovulation in young females is accounted for by an earlier rise in serum E2.     

Sexual behavior of castrated male rhesus monkeys treated with 19-hydroxytestosterone

The sexual behavior of 10 adult long-term castrated rhesus monkeys before and after treatment with 19-hydroxytestosterone (19-OH-T) was compared. Only the rate at which males contacted females increased significantly after treatment. The sexual behavior of these castrates was also compared with that of 8 untreated intact controls. Levels of estradiol-17β (E₂) and luteinizing hormone (LH) in peripheral plasma were determined by radioimmunoassay both before and after 19-OH-T treatment. After treatment, there was a significant increase in E₂ levels and a significant decrease in LH levels. Only the 5 males that had showed the ejaculatory response before treatment displayed it while undergoing treatment. These males had the lowest E₂ level during treatment whereas the 5 males that had failed to achieve intromission and ejaculation had the highest levels of E₂. The mounting rate correlated negatively with the level of E₂ in the blood.     

Effects of dihydrotestosterone on sexual behavior of castrated male rhesus monkeys

The sexual and sex-related behavior of 10 adult male rhesus monkeys castrated three years earlier was studied in pair tests with receptive females. Their performance before and during treatment with 1 mg/kg dihydrotestosterone propionate (DHTP) was compared. Nine unoperated adult males served as controls. DHTP effectively rendered the performance level of the castrates comparable to that of the intact controls.     

Selective changes in foraging behavior following bilateral neurotoxic amygdala lesions in rhesus monkeys

Across a variety of species, the amygdala appears to play a key role in the detection and avoidance of potential dangers (e.g., unfamiliar social partners, novel objects or contexts, potential predators, etc.). For many species, seeking out appropriate food sources and avoiding novel, distasteful or potentially tainted food is also a daily concern. Amygdala damage in nonhuman primates has been linked to increased willingness to select unfamiliar or unpalatable foods, as well as inedible items that intact animals typically reject. However, such findings have not always been consistent and have typically been observed in relatively restrictive, laboratory-based testing contexts. We evaluated the food choices of six adult male rhesus monkeys (Macaca mulatta) with bilateral, neurotoxic amygdala lesions and six age- and experienced-matched unoperated control animals. Each animal was able to forage freely in a large enclosure stocked with five preferred and five nonpreferred foods that changed locations each day. While both groups quickly selected palatable foods, monkeys with amygdala lesions consistently selected unpalatable foods that the unoperated control animals generally avoided. Even after repeated presentations of the unpalatable foods, the amygdala-lesioned monkeys failed to change their initial pattern of diminished avoidance. These results are consistent with a general role for the amygdala in danger detection and prevention of harm in the presence of novel or noxious stimuli, regardless of whether such stimuli are conspecifics, predators, objects or foods.     

Specific antibody levels in free-ranging rhesus monkeys: Relationships to plasma hormones,cardiac parameters,and early behavior

Levels of tetanus-specific antibodies were assessed in free-ranging, yearling rhesus monkeys following prophylactic immunization with tetanus toxoid. Each subject's behavior had been observed between 11 and 25 weeks of age and approximately 2 months later during its mother's first concentrated mating period as a part of another study. Prior to immunization, at approximately 1 year of age, cardiovascular parameters, and several plasma parameters [cortisol, adrenocorticotrophic hormone (ACTH), growth hormone (GH), interleukin-2 (IL-2), and total plasma immunoglobulin G (IgG)] were measured during a brief period of captivity. Antibody titers noted approximately 2 weeks after immunization were related to cardiovascular parameters. Thus, yearlings with high heart rates and low heart rate variability during captivity had the highest tetanus-specific serum IgG. Levels of plasma cortisol, ACTH, total IgG, and IL-2 noted at the time of capture were unrelated to subsequent antibody levels. Antibody titers were, however, positively correlated with GH noted immediately following capture on the day prior to immunization. Antibody titers were also related to the infants' behavior observed during their mother's first concentrated mating period, Infants who were most distressed (high levels of distress vocalization) when their mother resumed mating (a time particularly stressful for free-ranging rhesus infants) showed lower antibody titers to tetanus immunization as a yearling. The present observations add support to the existence of a relationship between behavior during exposure to an early stressor and later immune regulation and that certain cardiovascular parameters may be related to certain indicators of immunoregulation. © 1993 John Wiley & Sons, Inc.     

Auditory evoked potentials and auditory behavior following prenatal and perinatal asphyxia in rhesus monkeys.

Two types of asphyxia were studied in monkeys, total asphyxia during mid-pregnancy (94--98 days gestation) and combined partial and total axphyxia at term (165 days gestation). Auditory evoked potentials and the acquisition of 2 auditory discrimination tasks were studied in asphyxiated animals as well as in group of controls. The brains of all asphyxiates were examined histologically. No auditory discrimination deficit was found in the asphyxiated animals; however, the auditory evoked potentials differentiated between control and asphyxiated animals, especially those with verified inferior colliculus damage.     

Limited dissemination of pathogenic SIV after vaginal challenge of rhesus monkeys immunized with a live, attenuated lentivirus

In non-human primate models of AIDS, attenuated lentiviruses provide the most reliable protection from challenge with pathogenic virus but the extent to which the vaccine virus replicates after challenge is unclear. At 7 and 14 days after vaginal challenge with pathogenic SIVmac239, plasma SIVenv RNA levels were significantly lower in female macaques immunized 6 months earlier with live, attenuated SHIV89.6 compared to unimmunized control animals. In 2 SHIV-immunized, unprotected macaques SIV replication produced moderate-level plasma viremia with dissemination of challenge virus to all tissues on day 14 after challenge. In protected, SHIV-immunized monkeys, SIV replication was controlled in all tissues, from the day of challenge through 14 days post-challenge. Further, in CD8⁺ T cell-depleted SHIV-immunized animals, SIV replication and dissemination were more rapid than in control animals. These findings suggest that replication of a pathogenic AIDS virus can be controlled at the site of mucosal inoculation by live-attenuated lentivirus immunization.     

Chronic gonadotropin-releasing hormone agonist treatment suppresses ovulation and sexual behavior in group-living female rhesus monkeys

The sexual behavior of six adult rhesus females was observed with each of four males prior to, during, and following a 90 day treatment with 20 micrograms/day of a gonadotropin releasing-hormone (GnRH) agonist (WY-40972). All females ovulated, approached males and copulated during an untreated cycle. No ovulations occurred during agonist treatment and all females showed reduced sexual interest during the last 25 treatment days. Three females showed elevated estradiol and copulated during the first 10 days of agonist treatment, but never showed similar levels of estradiol or copulation during the rest of treatment. Within 34 days after agonist treatment, all females initiated proximity to males, copulated, and ovulated. All females became pregnant on their second ovulation after agonist treatment. This demonstration that inhibition of ovulation with a GnRH agonist decreased rhesus female sexual initiation, demonstrates the importance of ovarian hormones to female sexual motivation and suggests that the changes in human female sexual interest should be evaluated during the development of agonist-based contraceptives.