Kristine Coleman

Chronic Consumption of a High-Fat Diet during Pregnancy Causes Perturbations in the Serotonergic System and Increased Anxiety-Like Behavior in Nonhuman Primate Offspring

Childhood obesity is associated with increased risk of behavioral/psychological disorders including depression, anxiety, poor learning, and attention deficient disorder. As the majority of women of child-bearing age are overweight or obese and consume a diet high in dietary fat, it is critical to examine the consequences of maternal overnutrition on the development of brain circuitry that regulates offspring behavior. Using a nonhuman primate model of diet-induced obesity, we found that maternal high-fat diet (HFD) consumption caused perturbations in the central serotonergic system of fetal offspring. In addition, female infants from HFD-fed mothers exhibited increased anxiety in response to threatening novel objects. These findings have important clinical implications as they demonstrate that exposure to maternal HFD consumption during gestation, independent of obesity, increases the risk of developing behavioral disorders such as anxiety.

Growth hormone response to growth hormone-releasing hormone and clonidine in young monkeys: correlation with behavioral characteristics.

Blunted growth hormone (GH) release in response to stimulation by a secretagogue has been widely reported in both children and adults with anxiety and depressive disorders. Blunted GH responsiveness appears to be a stable characteristic of an individual, suggesting that it may be useful as a biological marker that would allow early recognition of these disease processes. Another potential biological marker for anxiety disorders is the temperamental construct of behavioral inhibition. Children identified as being behaviorally inhibited early in life are more likely than less inhibited children to suffer from anxiety disorders later in life (Biederman et al. 1993; Hirshfeld et al. 1992). If blunted GH responsiveness to pharmacological challenge and behavioral inhibition are markers of anxiety and depressive disorders, then it would follow that they would coexist in a subset of individuals. However, such prospective studies in clinically normal young children are difficult to perform. Therefore, in this study, we examined GH responsiveness and temperament in a group of 38 young rhesus monkeys (ages 3-6 months). Monkeys received an intravenous dose of 10 microg/kg of growth hormone-releasing hormone (GHRH) and 5 microg/kg of clonidine, combined, to assess GH response to stimulation. Behavioral reactivity in a fearful situation was assessed using the Human Intruder Test developed by Kalin et al. (1991). This test measures response to a potentially threatening stimulus (a human stranger making direct eye contact). Results showed a population distribution of GH response to GHRH and clonidine ranging from 120 ng/mL/90 minutes to 3,000 ng/mL/90 minutes. There was no difference in GH response in males versus females or any significant effect of age on GH response. There was a significant correlation between GH responsiveness and the time spent reacting to the intruder in the Human Intruder Test. Monkeys with lower GH responsiveness reacted less to the intruder (p < 0.01). Additionally, when monkeys were classified based on their reactivity in the Human Intruder Test, behaviorally nonreactive monkeys had significantly lower GH responsiveness than behaviorally reactive monkeys (p < 0.005). These data provide evidence that there are inherent differences in GH responsiveness to stimulation in young rhesus monkeys and that low GH responsiveness is linked to low behavioral reactivity, which may be a form of behavioral inhibition. Further studies will be necessary to determine if the characteristics of low GH responsiveness and low behavioral reactivity predict an increased propensity to develop anxious or depressive behaviors over the course of the life span.

IACUC review of nonhuman primate research.

This article will detail some of the issues that must be considered as institutional animal care and use committees (IACUCs) review the use of nonhuman primates (NHPs) in research. As large, intelligent, social, long-lived, and non-domesticated animals, monkeys are amongst the most challenging species used in biomedical research and the duties of the IACUC in relation to reviewing research use of these species can also be challenging. Issues of specific concern for review of NHP research protocols that are discussed in this article include scientific justification, reuse, social housing requirements, amelioration of distress, surgical procedures, and humane endpoints. Clear institutional policies and procedures as regards NHP in these areas are critical, and the discussion of these issues presented here can serve as a basis for the informed establishment of such policies and procedures.

Caring for nonhuman primates in biomedical research facilities: scientific, moral and emotional considerations

Animal care for nonhuman primates (NHPs) in biomedical facilities has undergone major changes in the past few decades. Today, most primate facilities have dedicated and highly trained animal care technicians who go to great efforts to ensure the physiological and psychological well being of the primates in their charge. These caretakers work closely with the animals and, as a result, often develop strong relationships with them. Once discouraged and considered a potential threat to scientific objectivity, such positive relationships are now seen as important components to animal care. Positive interactions between caretakers and primates can benefit the primates by reducing their stress and improving their overall well being which can, in turn, help the scientific endeavor. Further, providing the best possible care is our moral responsibility. However, there can also be emotional costs associated with caring for NHPs in research facilities, particularly when animals become ill or have to be euthanized. Facilities can do much to help ease this conflict. High‐quality and conscientious animal care is good for the animals, science, and public perception of research facilities. Am. J. Primatol. 73:220–225, 2011.

Relationships Between Androgens, Serotonin Gene Expression and Innervation in Male Macaques

Androgen administration to castrated individuals was purported to decrease activity in the serotonin system. However, we found that androgen administration to castrated male macaques increased fenfluramine-induced serotonin release as reflected by increased prolactin secretion. In this study, we sought to define the effects of androgens and aromatase inhibition on serotonin-related gene expression in the dorsal raphe, as well as serotonergic innervation of the LC. Male Japanese macaques (Macaca fuscata) were castrated for 5-7 months and then treated for 3 months with (1) placebo, (2) testosterone (T), (3) dihydrotestosterone (DHT; non-aromatizable androgen) and ATD (steroidal aromatase inhibitor), or (4) Flutamide (FLUT; androgen antagonist) and ATD (n=5/group). This study reports the expression of serotonin-related genes: tryptophan hydroxylase 2 (TPH2), serotonin reuptake transporter (SERT) and the serotonin 1A autoreceptor (5HT1A) using digoxigenin-ISH and image analysis. To examine the production of serotonin and the serotonergic innervation of a target area underlying arousal and vigilance, we measured the serotonin axon density entering the LC with ICC and image analysis. TPH2 and SERT expression were significantly elevated in T- and DHT + ATD-treated groups over placebo- and FLUT + ATD-treated groups in the dorsal raphe (p < 0.007). There was no difference in 5HT1A expression between the groups. There was a significant decrease in the pixel area of serotonin axons and in the number of varicosities in the LC across the treatment groups with T > placebo > DHT + ATD = FLUT + ATD treatments. Comparatively, T- and DHT + ATD-treated groups had elevated TPH2 and SERT gene expression, but the DHT + ATD group had markedly suppressed serotonin axon density relative to the T-treated group. Further comparison with previously published data indicated that TPH2 and SERT expression reflected yawning and basal prolactin secretion. The serotonin axon density in the LC agreed with the area under the fenfluramine-stimulated prolactin curve, providing a morphological basis for the pharmacological results. This suggested that androgen activity increased TPH2 and SERT gene expression but, aromatase activity, and neural production of estradiol (E), may subserve axonal serotonin and determination of the compartment acted upon by fenfluramine. In summary, androgens stimulated serotonin-related gene expression, but aromatase inhibition dissociated gene expression from the serotonin innervation of the LC terminal field and fenfluramine-stimulated prolactin secretion.

Behavioral Management, Enrichment, and Psychological Well-being of Laboratory Nonhuman Primates

Animal care in biomedical facilities housing nonhuman primates has undergone a dramatic transformation in the past two decades, with increasing emphasis on behavioral management, psychological well-being, and animal welfare. Today, providing for the psychological well-being of nonhuman primates is an integral part of animal care. Behavioral management is a comprehensive management strategy that includes enrichment, positive reinforcement training, facilities and enclosure design, positive staff–animal interactions, and behavioral monitoring in an effort to promote psychological well-being and animal welfare. Successful behavioral management strategies are tailored to the natural behavior of the species and include both social and nonsocial forms of enrichment. An increasing number of behavioral management programs include positive reinforcement training, a significant refinement to animal care practices. Appropriate behavioral management strategies can help reduce stress for nonhuman primates and prevent behavioral problems from occurring, which ultimately enhances the utility of the primate model in biomedical research. This chapter briefly summarizes several concepts that are integral to the appropriate behavioral management of laboratory primates and to the promotion of their psychological well-being and welfare.

Effects of aromatase inhibition and androgen activity on serotonin and behavior in male macaques.

Aggression in humans and animals has been linked to androgens and serotonin function. To further our understanding of the effect of androgens on serotonin and aggression in male macaques, we sought to manipulate circulating androgens and the activity of aromatase; and to then determine behavior and the endogenous availability of serotonin. Male Japanese macaques (Macaca fuscata) were castrated for 5-7 months and then treated for 3 months with (a) placebo; (b) testosterone (T); (c) T + Dutasteride (5a reductase inhibitor; AvodartTM); (d) T + Letrozole (nonsteroidal aromatase inhibitor; FemeraTM); (e) Flutamide + ATD (androgen antagonist plus steroidal aromatase inhibitor); or (f) dihydrotestosterone (DHT) + ATD (n = 5/group). Behavioral observations were made during treatments. At the end of the treatment period, each animal was sedated with propofol and administered a bolus of fenfluramine (5 mg/kg). Fenfluramine causes the release of serotonin proportional to endogenous availability and in turn, serotonin stimulates the secretion of prolactin. Therefore, serum prolactin concentrations reflect endogenous serotonin. Fenfluramine significantly increased serotonin/prolactin in all groups (p < .0001). Fenfluramine-induced serotonin/prolactin in the T-treated group was significantly higher than the other groups (p < .0001). Castration partially reduced the serotonin/prolactin response and Letrozole partially blocked the effect of T. Complete inhibition of aromatase with ATD, a noncompetitive inhibitor, significantly and similarly reduced the fenfluramine-induced serotonin/prolactin response in the presence or absence of DHT. Neither aggressive behavior nor yawning (indicators of androgen activity) correlated with serotonin/prolactin, but posited aromatase activity correlated significantly with prolactin (p < .0008; r² = 0.95). In summary, androgens induced aggressive behavior but they did not regulate serotonin. Altogether, the data suggest that aromatase activity supports serotonin production and that androgens increase aggression by another mechanism.

Responses to the Human Intruder Test are related to hair cortisol phenotype and sex in rhesus macaques (Macaca mulatta)

Measurement of cortisol in hair provides a chronic index of hypothalamic–pituitary–adrenal (HPA) axis activity and has been applied to assessments of temperament (stable behavioral differences between individuals). However, the extent to which chronically high HPA axis activity relates to a correspondingly high degree of behavioral reactivity is as yet unknown. Therefore, the goal of the present experiment was to assess the relationship between hair cortisol and a reactive temperament. We administered the Human Intruder Test (HIT) twice to 145 (80 male) rhesus macaques (Macaca mulatta) in order to assess behavioral reactivity. The HIT presents monkeys with an unfamiliar experimenter and is composed of a Baseline phase (no intruder) followed by three experimental phases in which the orientation of the intruder changes (Profile, Stare, Back). Behavioral responses to the test were videotaped and behaviors thought to reflect a reactive response to the intruder were scored for duration. Hair samples collected within ±1 month of the first HIT session were analyzed for cortisol by enzyme immunoassay. Subjects were assigned to three groups based on hair cortisol concentration: high, intermediate, and low cortisol phenotypes. Monkeys with the high cortisol phenotype were more reactive to the presence of the intruder than those with the low cortisol phenotype: they were more aggressive, scratched more, and spent more time in the back half of the cage. Males yawned significantly more while females spent more time immobile and in the back of the cage. Overall, monkeys with higher hair cortisol demonstrated an exaggerated response to the presence of the human intruder, supporting a relationship between high levels of chronic HPA axis activity and a reactive temperament. These results indicate that high levels of HPA axis activity, which may result from either genetic variation or environmental stress, correspond with heightened behavioral responses to a stressful experience. Am. J. Primatol. 79:e22526, 2017.

Assessing significant (>30%) alopecia as a possible biomarker for stress in captive rhesus monkeys (Macaca mulatta)

Hair loss is common in macaque colonies. Very little is known about the relationship between psychological stress and hair loss. We initially examined alopecia and hair cortisol concentrations in 198 (89 male) rhesus macaques from three primate centers and demonstrated replicability of our previous finding that extensive alopecia (>30% hair loss) is associated with increased chronic cortisol concentrations and significantly affected by facility. A subset of these monkeys (142 of which 67 were males) were sampled twice approximately 8 months apart allowing us to examine the hypotheses that gaining hair should be associated with decreases in cortisol concentrations and vice versa. Hair loss was digitally scored using ImageJ software for the first sample. Then visual assessment was used to examine the second sample, resulting in three categories of coat condition: (i) monkeys that remained fully haired; (ii) monkeys that remained alopecic (with more than 30% hair loss); or (iii) monkeys that showed more than a 15% increase in hair. The sample size for the group that lost hair was too small to be analyzed. Consistent with our hypothesis, monkeys that gained hair showed a significant reduction in hair cortisol concentrations but this effect only held for females. Coat condition changed little across sampling periods with only 25 (11 male) monkeys showing a greater than 15% gain of hair. Twenty (7 male) monkeys remained alopecic, whereas 97 (49 males) remained fully haired. Hair cortisol was highly correlated across samples for the monkeys that retained their status (remained alopecic or retained their hair). Am. J. Primatol. 79:e22547, 2017.

Rhesus macaque personality, dominance, behavior, and health

Previous studies of nonhuman primates have found relationships between health and individual differences in personality, behavior, and social status. However, despite knowing these factors are intercorrelated, many studies focus only on a single measure, for example, rank. Consequently, it is difficult to determine the degree to which these individual differences are independently associated with health. The present study sought to untangle the associations between health and these individual differences in rhesus macaques (Macaca mulatta). We studied 85 socially housed macaques at the Oregon and California National Primate Research Centers, and used veterinary records to determine the number of injuries and illnesses for each macaque. We measured personality using 12 items from a well‐established primate personality questionnaire, performed focal observations of behaviors, and calculated dominance status from directional supplant data. All twelve personality questionnaire items were reliable and were used to represent five of the six personality dimensions identified in rhesus macaques—Dominance, Confidence, Openness, Anxiety, and Friendliness (also known as Sociability). Following this, we fit generalized linear mixed effects models to understand how these factors were associated with an animals history of injury and history of illness. In the models, age was an offset, facility was a random effect, and the five personality dimensions, behavior, sex, and dominance status were fixed effects. Number of injuries and illnesses were each best represented by a negative binomial distribution. For the injury models, including the effects did improve model fit. This model revealed that more confident and more anxious macaques experienced fewer injuries. For the illness models, including the fixed effects did not significantly improve model fit over a model without the fixed effects. Future studies may seek to assess mechanisms underlying these associations.