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Biomedical subjects

S J Suomi

Publications and source records attributed to S J Suomi.

At least 19 recordsLinked to original sources
PubMed1992

A longitudinal assessment of CSF monoamine metabolite and plasma cortisol concentrations in young rhesus monkeys.

Twenty-two rhesus macaques were studied longitudinally from infancy to early adolescence in order to assess the effects of developmental change, experimental history, gender, and individual variation on the response of the catecholaminergic, serotonergic, and adrenocortical systems to separation-induced stress. Experimental effects were assessed by comparing subjects reared for the first 6 months of life either with their mothers or in peer groups. Developmental changes in response to repeated separation stress were assessed by subjecting the monkeys to four sequential 4-day social separations when they were 6 and 18 months old. At both ages, prior to, and on the last day of the first and fourth separations, cerebrospinal fluid (CSF) was obtained from the cisterna magna to assess monoamine metabolite concentrations, and blood samples were collected to assess plasma cortisol concentrations. Blood samples were also obtained on the first day of each separation at each age. Age-related declines were found in both homovanillic acid (HVA) and 5-hydroxyindoleacetic acid (5-HIAA) concentrations for all subjects. Social separation consistently increased CSF 3-methoxy-4-hydroxyphenolglycol (MHPG) over baseline levels, but decreased HVA concentrations, whereas 5-HIAA levels increased following the first, but not the fourth separation. Plasma cortisol increased rapidly immediately after separation and remained higher than baseline on day 4 of both the first and fourth separation. Independent of age and experimental condition, peer-rearing increased CSF MHPG and plasma cortisol concentrations. During year 1, peer-rearing also produced diminished CSF 5-HIAA concentrations in female monkeys relative to female mother-reared monkeys, but increased male peer-reared monkeys' concentrations relative to mother-reared males. Interindividual differences were highly stable, with significant correlations both within and between years for each of the three metabolites and cortisol.

Animals↗
PubMed1992

Cerebrospinal fluid monoamine and adrenal correlates of aggression in free-ranging rhesus monkeys.

Clinical and preclinical studies involving several different mammalian species and research paradigms suggest a negative correlation between aggression and central serotonin activity. To test the generalizability of laboratory findings in rhesus monkeys that show a negative correlation between cerebrospinal fluid 5-hydroxyindoleacetic acid concentrations and aggression, we obtained cisternal cerebrospinal fluid and blood plasma samples from monkeys living in naturalistic conditions. During a semiannual trapping, 28 juvenile and adolescent male rhesus monkeys were chosen from a population of 4200 provisioned, free-ranging rhesus monkeys living on Morgan Island, a sea island located off the coast of South Carolina. Based on direct observations of participation or avoidance of aggressive behavior and examinations of apparent fight wounds, 18 monkeys were selected for cerebrospinal fluid taps and blood samples. The remaining 10 monkeys were selected at random. Descriptions of aggressive behavior and the number of old scars and recent wounds were carefully transcribed, and a photograph showing wounds and scars was obtained for each animal. Using the transcriptions and photographs, researchers experienced in rhesus monkey behavior, but blind to the subjects' monoamine and hormone concentrations, were asked to rank the monkeys from the most to the least aggressive. The results showed a significant negative correlation between high rankings for aggression and cerebrospinal fluid 5-hydroxyindoleacetic acid concentrations. There was evidence that aggression was associated with stress, in that cerebrospinal fluid, norepinephrine, and plasma corticotropin and cortisol concentrations were positively correlated with high rankings of aggression.

Adrenocorticotropic Hormone↗
PubMed1991

Nonhuman primate model of alcohol abuse: effects of early experience, personality, and stress on alcohol consumption.

Twenty-two 50-month-old rhesus monkeys were provided concurrent free access to an aspartame-sweetened 7% ethanol solution and an aspartame-sweetened vehicle before, during, and after social separation. Subjects had been reared for their first 6 months of life either without access to adults but with constant access to age mates (peer reared), a condition producing reduced exploration and increased fear-related behaviors, or as controls with their mothers; thereafter, all subjects received identical treatment. During home-cage periods, for 1 hr each day, 4 days a week, when the ethanol solution and vehicle were freely available, peer-reared subjects consumed significantly more alcohol than mother-reared subjects. When stress was increased via social separation, mother-reared animals increased their alcohol consumption to a level nearly as high as that of peer-reared monkeys. Average individual differences in alcohol consumption were markedly stable over time. In addition, there were strong positive correlations between alcohol consumption and distress behaviors. Biological indices of increased stress, such as plasma cortisol and corticotropin, were higher in peer-reared subjects. Within the peer- and mother-reared groups, these indices were positively correlated with alcohol consumption. The results suggest that early rearing experiences that predispose monkeys to increased fear-related behaviors produce excessive alcohol consumption under normal living conditions. Furthermore, a major challenge such as social separation increases alcohol consumption to levels producing intoxication even in monkeys not particularly vulnerable to stress.

Alcohol Drinking↗
PubMed1991

Early stress and adult emotional reactivity in rhesus monkeys.

This chapter examines the relationship between early social experiences and behavioural and emotional reactivity in adolescence and adulthood that has been established through extensive research with rhesus monkeys. Classic studies carried out in the 1960s first demonstrated that rearing under conditions of social isolation resulted in severe behavioural abnormalities that carried over into adulthood. In the 1970s techniques for reversing such isolation-induced deficits were developed. More recent studies have examined the long-term consequences of more subtle variation in early rearing environments. Monkeys reared from birth without mothers but with extensive peer contact develop relatively normal social behavioural repertoires and function well in familiar and stable social settings. However, peer-reared monkeys display extreme behavioural and physiological reactions to environmental challenges, such as brief social separation, later in life. In contrast, monkeys reared by unusually nurturant foster mothers appear to develop effective strategies for coping with subsequent environmental challenges. Some general principles that have emerged from these studies with rhesus monkeys will be outlined and their implications regarding possible relationships between early social experiences and responses to challenge later in life in humans will be discussed.

Age Factors↗
PubMed1991

CSF monoamine metabolite concentrations vary according to age, rearing, and sex, and are influenced by the stressor of social separation in rhesus monkeys.

In humans, CSF monoamine metabolite concentrations have been shown to vary as a complex function of age, sex, psychiatric diagnosis, and stress. To test for such relationships in rhesus monkeys, 28 subjects, reared either in anxiety producing peer-only groups or in mother-infant dyads, were studied at 6, 18 or 50 months of age. Each monkey underwent a series of four 4-day social separations, each followed by 3 days of reunion. Prior to and during the first and fourth separations, CSF was obtained from the cisterna magna and assayed for the serotonin metabolite 5-HIAA, the dopamine metabolite HVA, and the norepinephrine metabolite MHPG. CSF 5-HIAA showed an age-related decline which was greater in the mother-reared subjects. Peer-only-reared males had an increased 5-HIAA concentration relative to females, and higher 5-HIAA levels than mother-reared males. MHPG was also higher in peer-only-reared monkeys than in mother-reared subjects at all ages. In both groups HVA declined across the three ages, and MHPG increased from the 18- to the 50-month measurements. Both MHPG and 5-HIAA concentrations increased during the initial social separation, although only MHPG remained elevated across the repeated separations; HVA, on the other hand declined during social separation. These results are discussed in terms of established anxiety and aggression differences between peer-only and mother-reared monkeys.

Aging↗
PubMed1991

Problem solving in elderly sophisticated and naive monkeys.

Elderly (greater than 23 years) rhesus monkeys, some of whom had previous learning test experience, were tested on a standardized battery of discrimination and concept-formation tasks, and their performance was compared with that of test-naive middle-aged (15 years) and juvenile (2 years) monkeys. Naive elderly monkeys performed more poorly on virtually all tasks compared to their younger counterparts. In contrast, test-experienced elderly monkeys outperformed both middle-aged and juvenile monkeys on those problem types with which they had limited previous experience, despite the fact that 8-10 years had passed since their prior training. However, test-experienced elderly monkeys did not display superior performance on new tests that approximated visual acuity or assessed delayed discrimination capabilities.

Aging↗
PubMed1991

Social interaction in nonhuman primates: an underlying theme for primate research.

Social living is assumed to be a critical feature of nonhuman primate existence inasmuch as most primate species live in social groups in nature. Recent USDA legislation emphasizes the importance of social contact in promoting psychological well-being and recommends that laboratory primates be housed with companions when consistent with research protocols. Our goals were to examine the link between social housing and psychological well-being and to explore the idea that research may be compromised when primates are studied in environments that vary too greatly from their natural ecological setting (individual cage housing versus group housing). Three general points emerge from these examinations. First, providing companionship may be a very potent way in which to promote psychological well-being in nonhuman primates; however, social living is not synonymous with well-being. The extent to which social housing promotes psychological well-being can vary across species and among individual members of the same species (for example, high- and low-ranking monkeys). Secondly, housing conditions can affect research outcomes in that group-housed animals may differ from individually housed animals in response to some manipulation. Social interaction may be a significant variable in regulating the biobehavioral responses of nonhuman primates to experimental manipulations. Finally, a larger number of socially housed subjects than individually housed subjects may be necessary for some biomedical research projects to yield adequate data analysis. Thus, social living has significant benefits and some potential costs not only for the animals themselves, but for the research enterprise.

Animals↗
PubMed1989

Pituitary--adrenal response to capture in Cayo Santiago--derived group M rhesus monkeys.

113 rhesus monkeys, representing 4 age classes, 3 matrilines, and immigrant adult males in a 161-member Cayo Santiago-derived troop living in a 2-acre enclosure, were sampled for levels of plasma ACTH and cortisol during a period of capture and brief cage confinement for routine veterinary examination. ACTH levels showed significant decreases over initially high values following capture in all subjects except infants, whereas cortisol levels remained elevated throughout the sampling period. Members of the lowest-ranking matriline had significantly higher ACTH levels than members of the other matrilines and immigrant males. Infants and juveniles exhibited higher cortisol levels than adolescent and adult monkeys. The overall pattern of results was generally consistent with previous findings from laboratory studies, providing not only evidence of generality across conditions and subject populations but also the basis for more detailed subsequent analyses of the relationship between pituitary-adrenocortical responsiveness, behavioral response to challenge, and age-sex-dominance status in wild-born rhesus monkeys.

Academies and Institutes↗
PubMed1989

Heart rate and endocrine responses to stress in adolescent male rhesus monkeys on Cayo Santiago.

Patterns of stress-responsiveness were studied in 19 adolescent male rhesus monkeys (Macaca mulatta) who are part of the free-ranging colony on Cayo Santiago, PR. Morphometric and blood samples were obtained as each male was captured and after holding overnight. Subject heart rate was recorded on Day 2, using surface EKG telemetry. Males showed marked individual differences in cardiac and endocrine profiles which were generally unrelated to their age, size or maternal rank. Heart rate patterns were correlated with several endocrine measures: males with low and variable heart rates showed lower cortisol, higher-prolactin and higher growth hormone levels on Day 2 relative to males with higher and less variable heart rates, and their testosterone levels increased rather than decreased. Males with low and variable heart rates appear to have an endocrine response profile that is less adversely affected by acute stress, and which may potentially give them a competitive advantage in social interactions.

Academies and Institutes↗
PubMed1988

Rearing paradigm in a nonhuman primate affects response to beta-CCE challenge.

Two groups of socially housed rhesus monkeys were raised under conditions differing in the degree of control or mastery over appetitive stimuli (food, water, and treats) in the 1st year of life. At age 18-24 months, a benzodiazepine receptor inverse agonist, beta-carboline-3-carboxylic acid ethyl ester (beta-CCE), was administered to both social groups to investigate the effects of differential rearing on the response to a putative anxiogenic drug. In both groups beta-CCE was followed by behavioral activation with a profile suggesting increases in aggression rather than fear or anxiety. A group by drug analysis revealed that the increase in aggression was observed predominantly in the subjects reared with mastery during the 1st year. Plasma cortisol increased in both groups, but its increase was greater in the yoked subjects. These results suggest that early experience with controllability may have long term consequences which can be revealed by challenge with beta-CCE.

Aggression↗
PubMed1987

Preferences of female rhesus monkeys (Macaca mulatta) for infantile coloration.

While developmental researchers have long noted that infants of many mammalian species, including primates, have characteristic physical features, such as a distinctive coat or skin color, and some authors have further suggested that these features serve to elicit caretaking and solicitous behavior, few systematic investigations of the actual salience of such features for adult conspecifics have been carried out to date. The present series of 3 studies sought to determine whether natal coat and/or facial skin coloration might provide desirable visual stimulation for rhesus monkey adult females. In these studies the faces and/or fur of 6-month-old rhesus monkeys were dyed to simulate the normal coloration of rhesus monkey neonates. Adult females varying in parity and rearing history were then tested for their relative preference between these infantile-colored 6-month-olds and both normally colored 6-month-olds and other differentially colored control stimulus monkeys. Results indicated that regardless of parity or rearing history the adult female subjects exhibited consistent preferences for the stimulus animals with neonatal-like reddish-pink facial skin coloration.

Animals↗