Long-term chlorpromazine in rhesus monkeys: production of dyskinesias and changes in social behavior

The daily administration of chlorpromazine (CPZ) in doses of 8--40 mg/kg over 113 weeks to four rhesus monkeys produced dyskinesias and alterations in social behavior. General activity and social interactions were reduced by CPZ treatment but social aggression was elevated during initial drug administration. These behaviors returned to normal when treatment was discontinued. Dyskinesias appeared during CPZ treatment, and two striking ones, gravel mouth and hand gesture, persisted for 12 weeks after drug withdrawal. These results indicate that dyskinesias which share major features of human tardive dyskinesia can be produced in nonhuman primates by long-term CPZ treatment.

Use of 6-hydroxydopamine to deplete brain catecholamines in the rhesus monkey: effects on urinary catecholamine metabolites and behavior

The purpose of this study was to determine: 1) whether 6-hydroxydopamine (6-OHDA), previously shown to deplete brain catecholamines (CA) in rodents, depletes brain CA in rhesus monkeys; 2) whether depletion of brain CA produces changes in behavior; and, 3) whether urinary output of 3-methoxy-4-hydroxyphenylglycol (MHPG) reflects brain norepinephrine (NE) depletions. Repeated intracerebroventricular (ICV) injection of 6-OHDA (N = 20; 15.5-73.3 mg/subject) produced chronic changes in social behavior and, at higher dosages, reduced output of urinary MHPG. However, 4 weeks after the last ICV 6-OHDA injection, urinary MHPG excretion returned to baseline values and whole brain CA content was not reliably different from control. A single treatment with 6-OHDA microinjected into the substantia nigra (SN) (N = 12; 120-240 microgram/subject) produced chronic whole brain depletions of brain CA without depleting serotonin. Reductions in brain CA were associated with a specific set of motor behaviors, aphagia, and adipsia. SN 6-OHDA produced greater brain NE depletions than ICV 6-OHDA, but urinary MHPG output was not reduced. SN 6-OHDA treated subjects showed chronic changes in social behavior and were more sensitive to the operant response rate decreasing effects of alpha-methyl-para-tyrosine (AMPT) than control subjects. Subjects with the largest depletions of brain dopamine (DA) (greater than 90%) were hypokinetic, rigid, and had a distal limb tremor. These results show that SN but not ICV injection of 6-OHDA can deplete brain CA in the rhesus monkey. The most prominent behavioral changes were characterized by disturbances in motor function. Urinary MPHG output does not reflect depletions of brain NE in this species.

Overview of the past contributions of animal models and their changing place in psychiatry

Research utilizing animal models has been responsible for major advances in understanding psychiatric disorders. The first data based integrative theories of psychopathology grew largely out of animal research. A variety of animal models that have been developed have been critical in broadening our understanding of human development and in providing empirical support for the importance of early experiences for behavioral and neurobiologic development. The development of many widely used clinical psychopharmacologic agents has depended on the use of animal models. The above examples represent substantive contributions of animal models to investigations of fundamental aspects of psychopathology. There is no "perfect," complete or comprehensive single animal model for any specific psychiatric disorder and contentious debates about the validity and/or usefulness of specific animal models persist. Animal models of diseases in medicine need to be understood in a historical and evolutionary perspective and their advantages as well as limitations recognized. There will likely never be an animal model in any field of medicine that is a perfect fit with the human condition, rather the emphasis in the development and study of disease models in animals needs to be on specific components of the human illness. Neither overextended cross-species comparisons nor unjustified negativism about animal models seems defensible. A major challenge in the continuing development and use of biobehavioral animal models in psychiatry is their relationship to the molecular neurosciences, including genetics, in understanding the mechanisms of mental disorders.

Biogenic amine activity in response to fluoxetine and desipramine in differentially reared rhesus monkeys

BACKGROUND

It has been hypothesized that adverse early experience may be a mechanism by which children become vulnerable to later psychopathology via alteration of neurochemical or hormonal systems associated with such disorders. Such effects may in turn affect later responses to pharmacologic agents that act on these systems.

METHODS

In this study, 18 mother-reared (MR) and 18 peer-reared (PR) rhesus monkeys experienced six 1-week separations from cagemates interspersed with 1-week reunions, while housed in like-reared groups of 3. Within rearing groups, equal numbers of animals received either fluoxetine (2 mg/kg), desipramine (5 mg/kg) or placebo delivered daily beginning 4 weeks before the first separation. Levels of norepinephrine (NE), the NE metabolite MHPG, the dopamine metabolites DOPAC and HVA, and the serotonin metabolite 5HIAA were measured in CSF samples collected approximately every 2 to 3 weeks during these procedures.

RESULTS

Following treatment, DMI increased NE and decreased MHPG in the DMI-treated groups, while 5HIAA was decreased in the fluoxetine-treated groups following treatment. The increase in NE was followed by a sharp decline over the course of treatment, which was accompanied by an increase in MHPG. The rearing groups did not show a differential response to the drug treatments, and the separation manipulation itself had few effects. The mother-reared group showed higher levels of NE and DOPAC over all samples and higher levels of HVA in most samples.

CONCLUSIONS

These rearing effects on biogenic amine activity were observed even in the presence of pharmacologic treatments that effectively altered the activity of these systems, and are consistent with previous findings from the same subject. The higher NE values observed in mother-reared infants over separations and reunions may have been due to higher basal levels of NE than peer-reared monkeys or to greater responsiveness to the stress of repeated social disruption or both. These findings agree with other primate studies showing that rearing differences persist beyond the infancy period and add to growing evidence of the important influence of the early social environment on neurobiologic development in primates.

Rearing experience and biogenic amine activity in infant rhesus monkeys

In this report we present evidence that early social experience influences aspects of the function of brain biogenic amine systems, most notably the noradrenergic system. Biogenic amine activity was studied in mother- vs. peer-reared monkey infants over the first 6 months of life and in response to two housing transitions. Norepinephrine (NE), 3-methoxy-4-hydroxyphenylglycol (MHPG), dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA), and 5-hydroxyindoleacetic acid (5-HIAA) levels in cerebrospinal fluid (CSF) were measured. Peer-reared monkeys showed significantly higher CSF levels of norepinephrine and MHPG than mother-reared animals over early development, but showed an attentuated NE response to separation and group formation compared to mother-reared animals. Peer-reared monkeys showed a greater developmental decline in 5-HIAA levels than mother-reared monkeys. There were no rearing effects for DOPAC or HVA over early development; however, peer-reared monkeys showed significantly lower HVA and DOPAC concentrations at 6-8 months of age. The results add to evidence for the influence of primate mothers on the psychobiological development of central nervous system neurotransmitter systems in their infants, and suggest that the noradrenergic system is among the more sensitive of these to early experience.

Evidence for heritability of biogenic amine levels in the cerebrospinal fluid of rhesus monkeys

Susceptibility to several human psychopathological disorders is under partial genetic influence, and many of these disorders have biological correlates that may form part of the basis of this vulnerability. In humans, alterations in cerebrospinal fluid (CSF) metabolite levels of the amine transmitters norepinephrine, dopamine, and serotonin have been associated with several forms of psychopathology, and altered levels of these metabolites have been found in healthy probands with a familial history of such illnesses. We report evidence for heritability of CSF levels of biogenic amine measures in rhesus monkeys, Macaca mulatta. In a pilot study of 54 monkeys with known pedigrees, significant differences among sire families were found for CSF levels of norepinephrine (p = 0.04), homovanillic acid (p = 0.02), and 5-hydroxyindoleacetic acid (p = 0.04). These data indicate that variation in bioaminergic measures is associated with pedigree, and that model systems incorporating both genetic and environmental factors can contribute to the understanding of the function of aminergic systems implicated in vulnerability to psychopathology.

The noradrenergic innervation density of the monkey paraventricular nucleus is not altered by early social deprivation

A series of neuroanatomic analyses have been undertaken to identify potential neuropathological changes seen in monkeys exposed to early social deprivation, which leads to psychopathology, inappropriate responses to stress and appetitive disorders. The animals used in this study were either socially reared or maternal- and peer-deprived. Within this framework, the distribution and density of noradrenergic (and adrenergic) varicosities was assessed in the hypothalamic paraventricular nucleus of rhesus monkeys using dopamine-beta-hydroxylase immunohistochemistry combined with laser scanning microscopy. Quantitative analysis of dopamine-beta-hydroxylase-immunoreactive varicosity density within magnocellular and parvicellular regions revealed no significant differences between rearing conditions, suggesting that this chemically identified afferent input to the paraventricular nucleus was not affected by the early environmental insult of social deprivation. The apparent lack of vulnerability of the paraventricular nucleus to differential rearing conditions contrasts with the neuropathological changes observed in several discrete brain regions.

Effects of social deprivation in prepubescent rhesus monkeys: immunohistochemical analysis of the neurofilament protein triplet in the hippocampal formation

Social deprivation during early postnatal life has profound and long-lasting effects on the behavior of primates, including prolonged and exaggerated responses to stress as well as impaired performance on a variety of learning tasks. Although the cellular changes that underlie such alterations in behavior are unknown, environmentally induced psychopathology may involve morphologic or biochemical changes in select neuronal populations. The hippocampal formation of both socially deprived and socially reared prepubescent rhesus monkeys was selected for immunocytochemical investigation because of its association with the behavioral stress response and learning. Immunocytochemical analysis using antibodies specific for the neurofilament protein triplet was performed since these proteins are modified within degenerating neurons in a variety of neurodegenerative disorders. Results from optical density measurements indicate an increase in the intensity of non-phosphorylated neurofilament protein immunoreactivity in the dentate gyrus granule cell layer of socially deprived monkeys in comparison with that of socially reared animals, suggesting that early social deprivation may result in an increase in the amount of non-phosphorylated neurofilament protein in these cells. This phenotypic difference in dentate granule cells between differentially reared monkeys supports the notion that specific subpopulations of neurons in brain regions that subserve complex behaviors may undergo long-term modifications induced by environmental conditions. Furthermore, the data suggest that constitutive chemical components related to structural integrity may be as susceptible to early environmental manipulations as the more traditionally viewed measures of cellular perturbations, such as neurotransmitter dynamics, cell density and the establishment of connectivity. The observed modifications may serve as an anatomical substrate for behavioral abnormalities that persist in later life.

Quantitative analysis of tuberoinfundibular tyrosine hydroxylase- and corticotropin-releasing factor-immunoreactive neurons in monkeys raised with differential rearing conditions

A major goal in assessing biological determinants of behavior lies in studying the effect(s) of rearing on the development of the central nervous system. Specifically, a series of neuroanatomic analyses have been undertaken to identify potential neuropathological changes seen in monkeys exposed to early social deprivation, which leads to profound psychopathology and inappropriate responses to stress. The animals used in this study were either raised with their mother and peers (socially reared) or raised without maternal/peer contact (socially deprived). Within this context, the distribution of tuberoinfundibular dopaminergic neurons in the hypothalamic paraventricular nucleus and arcuate nucleus of rhesus monkeys was determined by immunohistochemistry using an antibody against the enzyme tyrosine hydroxylase, a marker for dopamine-containing systems. Additionally, the distribution of corticotropin-releasing factor-containing neurons in the paraventricular nucleus was assessed immunohistochemically. The majority (97.5%) of dopaminergic neurons in the paraventricular nucleus were parvicellular, with a small (2.5%), but consistently observed population of magnocellular neurons immunoreactive for tyrosine hydroxylase. Within the arcuate nucleus, tyrosine hydroxylase-immunoreactive neurons were similar in morphology to the parvicellular neurons of the paraventricular nucleus. Qualitative assessment of corticotropin-releasing factor-immunoreactive neurons in the paraventricular nucleus revealed a parvicellular population of neurons located in medial aspects of the nucleus, similar to what has been observed in the rat. Quantitative analysis revealed no differences in the number of tyrosine hydroxylase- and corticotropin-releasing factor-immunoreactive neurons between rearing conditions, suggesting that these neurons were not affected, in terms of overall cell counts, by the early environmental insult of social deprivation.

Strangers in a strange land: a psychobiological study of infant monkeys before and after separation from real or inanimate mothers

Some rhesus monkey (Macaca mulatta) infants have a "despair" or depression-like response to mother-infant separation, while others do not. The presumed interrelation between early rearing conditions and the neurobiological status of the infant that might lead to increased risk for despair is not understood. In this study, the characteristics of the "mother" were controlled by rearing infant rhesus monkeys with their biological mothers, or with inanimate mothers. Behavioral data were collected before and after separation at 6-7 months of age. The neurobiological status of the infants was evaluated by measuring the concentration of norepinephrine, its major metabolite, and the metabolites of dopamine and serotonin in cerebrospinal fluid. The results suggest that despair is not simply a behavioral response to separation. Instead, despair may reflect the inability to cope with the separation environment. Coping with the separation environment appears to depend on neurobiological and behavioral characteristics of the infant that are related to, if not determined by, characteristics of the mother.

A longitudinal study of the effect of different social rearing conditions on cerebrospinal fluid norepinephrine and biogenic amine metabolites in rhesus monkeys

The purpose of this study was to determine whether disruption of early social attachment alters the activity of brain biogenic amine systems in rhesus monkeys (Macaca mulatta). Male rhesus monkey infants were deprived of maternal interaction, peer interaction, or both, during the first 22 months of life. Cerebrospinal fluid (CSF) was collected under rigorously controlled conditions approximately every month and assayed for levels of norepinephrine (NE), its major metabolite, and the metabolites of dopamine and serotonin. Mother-Deprived infants had lower levels of CSF NE than Mother-Reared infants. Mother-Deprived infants also failed to develop the same pattern of intercorrelations between compounds and month-to-month stability in levels of neurotransmitter and metabolites in CSF as the Mother-Reared infants. Finally, there were changes in CSF NE levels associated with social separation and social group formation. The brain NE system appears to be sensitive to changes in the social environment. Its level of activity, as reflected in levels of NE in CSF, appears to depend on both the prevailing social environment and the prior rearing environment.

Social separation increases alcohol consumption in rhesus monkeys

This study used 16 socially reared juvenile rhesus monkeys as subjects to test the hypothesis that social separation promotes alcohol consumption in this species. In the first part of the study, 12 monkeys were intermittently separated from their social groups, while 4 were separated before the beginning of the study and remained continuously separated. Refrigerated water or aspartame-sweetened water (vehicle) containing 6% alcohol (w/v) were presented after 4.5 h of fluid deprivation. Intermittently separated monkeys drank more alcohol during separation than when they were socially housed, and more than the continuously separated monkeys. Stable individual differences in consumption rate developed over repeated separations. These differences were not correlated with consumption of refrigerated water or vehicle, or with differential behavioral (locomotor) responses to social separation. This suggested that some monkeys were predisposed to drink more alcohol than others. The second part of the study determined whether established alcohol/vehicle consumption rates for all 16 monkeys were altered when the monkeys were not water deprived, and then when water and the vehicle were available at the same time as alcohol/vehicle. Among monkeys that drank the most (mean of 2.4 g/kg/h) and the least (mean of 0.8 g/kg/h), alcohol consumption was not affected. These results, combined with previous reports, suggest a neurobiological linkage between genetically based social attachment mechanisms, social stressors, and vulnerability to alcohol abuse and addiction in primates.

Effects of alcohol on cerebrospinal fluid norepinephrine in rhesus monkeys

Alcohol (1-3 g/kg) significantly increased the concentration of cerebrospinal fluid (CSF) norepinephrine (NE) in rhesus monkeys. This effect is consistent with the previously demonstrated activational and possible antidepressant effect of low doses of alcohol. The greatest increase was observed in subjects with low baseline levels of CSF NE. Individual differences in activation or euphoria could be related to differential increases in CSF NE following alcohol consumption.

Cerebrospinal fluid measures of neurotransmitter changes associated with pharmacological alteration of the despair response to social separation in rhesus monkeys

Social separation is a risk factor for major depressions that can be modeled in nonhuman primates. Changes in central monoamine neurotransmission are also likely to be involved in major depression. This study examined the relationship between separation-induced depressive-like behavior and central monoamine neurotransmitter changes in rhesus monkeys. Measures of cerebrospinal fluid (CSF) norepinephrine (NE), 5-hydroxyindoleacetic acid (5HIAA), and homovanillic acid (HVA) were used to assess the neurobiological impact of social separation and drug treatments alone or in combination. alpha-Methyl-p-tyrosine exacerbated, and fusaric acid ameliorated, the depressive-like response to separation. Probenecid-induced accumulations of HVA and 5HIAA reflected changes in behavior, but were not consistently affected by drug treatment. In contrast, pretreatment CSF NE was comparatively stable across repeated sampling, and drug-induced changes in this measure were correlated with changes in behavior. Low CSF NE, whether drug-induced or naturally occurring, was associated with a more severe depressive-like response to separation.

Hypersensitivity to d-amphetamine several years after early social deprivation in rhesus monkeys

Social deprivation of rhesus monkeys in infancy results in increased sensitivity to psychotic-like behavioral effects of low doses of d-amphetamine given 2-3 years later. These behavioral effects are associated with increased levels of CSF norepinephrine. These data suggest that social developmental factors could be partially responsible for variation in neurochemical responses and long-lasting differential sensitivity of primates to the psychosis-inducing effects of d-amphetamine.

Associated endocrine, physiological and behavioral changes in rhesus monkeys after intravenous corticotropin-releasing factor administration

The intravenous (IV) administration of synthetic ovine corticotropin-releasing factor (CRF) (10 and 125 micrograms/kg) to chair restrained rhesus monkeys stimulated the pituitary-adrenal axis. At these doses, increases in plasma concentrations of adrenocorticotropic hormone (ACTH) and cortisol were associated with blood pressure decreases and behavioral effects. These data demonstrate that synthetic ovine CRF (10 and 125 micrograms/kg) administered IV to the rhesus monkey results in associated endocrine, physiological, and behavioral changes.

Corticotropin-releasing factor administered intraventricularly to rhesus monkeys

Synthetic ovine corticotropin-releasing factor (CRF) administered intraventricularly (ICV) to rhesus monkeys resulted in endocrine and behavioral changes. At doses of 20 and 180 micrograms, CRF stimulated the pituitary-adrenal axis in four chair-restrained monkeys. These monkeys showed concomitant increases in arousal. To study these animals in a less restrictive setting, three of the monkeys later received CRF ICV (20 and 180 micrograms) in their home cages. At the 180-micrograms dose the monkeys exhibited a combination of huddling and lying down behavior. These behavioral effects did not seem to be due to alterations in blood pressure.

Animal models of schizophrenia

The authors review some general issues concerning the development and use of animal models of schizophrenia and present a summary of the criteria necessary for validating models. They also describe some of the major attempts at creating animal models of schizophrenia, including drug and nondrug methods. They comment on the etiologic, phenomenologic, and treatment relevance of the various systems and suggest approaches that might produce improved animal models of schizophrenia.

The dexamethasone suppression test as a measure of hypothalamic-pituitary feedback sensitivity and its relationship to behavioral arousal

A nonhuman primate model was used to evaluate the value of the dexamethasone suppression test as an index of hypothalamic-pituitary-adrenal responsiveness to arousal. In 8 rhesus monkeys plasma cortisol was suppressed by dexamethasone in a dose-dependent fashion at doses between 0.75 and 33 microgram/kg. A replication study was performed 5 months later using a single dexamethasone dose (17 microgram/kg) known to produce maximal plasma cortisol suppression. This yielded highly correlated results (r = 0.91, p less than 0.005) suggesting that dexamethasone suppressibility may be a stable characteristic of individual animals. In 9 other animals whose arousal responses to a stressful procedure (nasogastric tube insertion) had been rated daily over a previous 3-month period, baseline plasma cortisol levels and the percent suppression of plasma cortisol by dexamethasone were evaluated. Baseline plasma cortisol levels did not significantly correlate with the degree of dexamethasone-suppression and the mean arousal ratings within animals. However, the postdexamethasone percent of baseline cortisol did correlate significantly (r = 0.75, p less than 0.025) with individual mean arousal ratings. These preliminary results suggest that assessment of the sensitivity of an individual's hypothalamic-pituitary glucocorticoid feedback system may be a better predictor than its baseline cortisol concentrations of its degree of behavioral arousal to stress.

Effects of alcohol on the despair response to peer separation in rhesus monkeys

In humans, alcoholism and depression are often interrelated. This study examines the effects of alcohol on peer separation-induced despair in rhesus monkeys, a proposed nonhuman primate model of depression. Alcohol, at three different dose levels, or placebo was administered to rhesus monkeys undergoing repeated peer separation. Low-dose alcohol (1 g/kg/day) decreased separation-induced despair, whereas high-dose alcohol (3 g/kg/day) exacerbated the despair response as compared to placebo. This biphasic effect of alcohol on the despair response may be analogous to similar effects of alcohol on depression in humans.

Mutual antagonism of behavioral effects of TRH and thiobarbiturate on an operant task in rhesus monkeys

Similar excitatory or depressant response rate dependent effects on monkeys responding on a variable interval reinforcement schedule were observed following intravenous administration of either thyrotropin releasing hormone (TRH) or thiobarbiturate. However, these agents were mutally antagonistic when given together even though the response rate altering effects of each agent were in the same direction. These findings establish an additional behavioral effect of exogenously administered TRH in primates and suggest that barbiturates might alter behavior in part through an interaction with brain TRH receptive mechanisms.

Interactions of pharmacological agents which alter biogenic amine metabolism and depression--an analysis of contributing factors within a primate model of depression

The observation that the biogenic amine depleting agent, reserpine, could induce severe depression in a small proportion of the patients treated with it has proved to be seminal finding in what is now a much larger field of research relating the function brain biogenic amine systems to emotions and behavior. A review of the human reserpine literature suggests, however, that factors other than pharmacologically produced alterations in brain biogenic amine metabolism must have been critical determinants of the eventual mood alterations observed in conjunction with reserpine treatment. While some of these factors, such as previous history of depression, ongoing psychosocial and environmental stress, can be intuitively identified, there are practical as well as ethical problems involved in actually testing the relative contribution of these factors in precipitating human depression and thereby determining their importance in a quantitative fashion. In the present paper we have attempted to examine, in a nonhuman primate model of depression, the degree to which factors such as prior rearing condition, repeated peer separation, and housing environment can intact with the behavioral effects produced by biogenic amine depleting agents. Major emphasis will be placed on studies utilizing alpha-methyl-para-tyrosine, an inhibitor of tyrosine hydroxylase, to ostensively reduce levels of the catecholamine neurotransmitters norepinephrine and dopamine. The results of these studies provide quantitative estimates, in terms of dose-effect relationships, of the degree to which a number of factors can combine to produce despair-like behavior in rhesus monkeys. These data may be of practical importance in evaluating the contribution of similar factors to the precipitation of human depression. Analysis of some of the existing literature relating alterations in behavior to changes in biogenic amine metabolism in animals suggests that there are important differences between rodent and primate species. These differences, when fully established, may indicate that additional research examining the mechanisms whereby modest alterations in biogenic amine metabolism can interact with environmental and social stress is needed.

The overlapping territories of psychiatry and ethology

There have been numerous attempts since 1965 to stimulate more utilization of ethological methods and concepts in psychiatry. This literature is reviewed and an attempt is made to identify the factors which have inhibited an enhancement of this interaction to date. Most of the previous articles on this subject have appeared in edited collections, rather than in more widely circulated psychiatric or medical journals. Some of the articles focus on ethological theory, others on ethological research findings, and several on clinical analogies between animal and human situations. Regarding the specific way in which to integrate ethological thought into psychiatry, most frequently a phylogenetic approach is emphasized, however a few authors stress methodological considerations. In this paper, it is argued that artifactual differences have been the primary impediment to more interaction between these two rather similar fields. Scientific language difficulties, educational differences, and personal factors are described in this regard. Also, the real differences in approach and methodology, relative interest in normal vs. abnormal behavior, the degree of willingness to accept a phylogenetic approach, and the breadth of behavior being studied by the two fields are described. Examples of current areas of applicability of ethology to psychiatry are given: the attachment systems, early infantile autism, methodology, social psychiatry, and psychiatric education. Of these, the area where the most utilized is that of the occurred and in which the findings of ethology have been the most utilized is that of the attachment systems. Clinically applicable studies based upon the premise that attachment systems exist as understood ethologically are reviewed. These include study of extra physical contact between mothers and infants at birth, the prediction of child abuse and neglect utilizing observations from the immediate postpartum period, the treatment of failure to thrive by teaching attachment behavior, and developmental differences at 1 year correlated with differences in maternal responsiveness at 3 months. The usefulness of a biological approach to behavior is discussed, particularly in terms of utilizing operational criteria and from the point of view of differentiating etiological, phenomenological, and treatment models. A curriculum stressing the writings of Tinbergen, Lorenz, Bowlby, and Hailman is presented for possible use in psychiatric training programs interested in teaching an ethological approach to psychiatry. A briefer curriculum is also suggested from the psychiatric literature for use by ethologists. The epistemology and methodology of ethology possible will be of more use to psychiatry than the content. It is the opinion of the authors that the difficulties which have inhibited significant cooperation between psychiatry and ethology in the past are mostly artifactual, that such cooperation could be useful to both fields, and that a beginning to such interaction will require mutual familiarity with the literature.

Use of pneumoencephalography to increase stereotaxic accuracy in rhesus monkeys

A radiographic method for visualizing intracranial structures for stereotaxic surgery is described. The procedure circumvents the problems associated with the use of radiopaque dyes, and it does not require modification of standard stereotaxic equipment. Anatomical data derived from the use of the method are presented, as well as an example of its application for accurately placing cannulae in the midbrain.

Effects of imipramine treatment of separation-induced social disorders in rhesus monkeys

Two groups of young rhesus monkeys were subjected to repetitive peer separations, a procedure that has been shown to produce depressivelike reactions in infant monkeys. Midway through the procedure one group was treated with the antidepressant imipramine hydrochloride, the other with a saline placebo. In comparison with placebo treatment, the imipramine treatment yielded significant behavioral improvement in a form and with a time course similar to that seen when the drug is given clinically to human depressives. We discuss the implications of the findings.

The effect of electrically induced convulsions on the behavior of normal and abnormal rhesus monkeys

The social behavior of six juvenile rhesus monkeys was studied in a playroom before, during, and after a series of electrically induced convulsive (EIC) treatments. Three subjects had been reared in a normal environment, and showed the usual levels of social activity for monkeys of this age. Three were socially deprived early in life and showed higher levels of self-directed behaviors and lower levels of social behaviors. At different times all animals received both EIC ad sham EIC, three times per week for 4 weeks, and were observed in a playroom. In general the experimental subjects showed an increase in environmental activity as a consequence of EIC treatments while the control subjects showed decreases in environmental activity and in several social behaviors. The control subjects showed clear increases in self-disturbance behaviors while the experimental animals tended to show a decrease. The patterns of these changes thus showed clearly different characteristics of response to EIC and sham EIC as a function of early rearing condition. The results are discussed in terms of possible models for further study of the effects of EIC on physiological and social variables in a controlled laboratory setting.

Diazepam treatment of socially isolated monkeys

Four rhesus monkeys were reared for the first eight months of life in total social isolation. One animal died during this period; the three remaining subjects were treated with diazepam in an isolation chamber, in their home cages, and in a playroom testing situation. Diazepam significantly decreased the self-disturbance behaviors of two subjects, and there was even the appearance of some social behaviors, although they were limited and not of the same quality as in nonisolated subjects. The authors discuss the implications of the data for understanding the significance of the social isolation syndrome in monkeys as a model for human psychoses.

Mother-infant separation in rhesus monkeys as a model of human depression. A reconsideration

Nineteen rhesus monkeys between the ages of 5.9 and 8.5 months were separated from their mothers in five different studies. While in two of the studies, data indicated behavioral responses roughly parallel to Bowlby's protest-despair response to maternal separations, data across all five studies were sufficiently variable to bring this technique into serious question as a reliable and predictable animal model for neurobiologic and rehabilitative studies.

Thyrotropin releasing hormone: antagonism of pentobarbital narcosis in the monkey

The effect of TRH on pentobarbital narcosis in 21 rhesus monkeys was examined. Vital signs monitored included respiration rate, heart rate, temperature, sleeping time,and time of reappearance of certain reflexes. Blood samples were obtained for pentobarbital assay. Two dose schedules for TRH administration were used. One group of 6 animals received a single dose of 20 mg/kg 30 min after barbiturate administration, while the other group were received 3 injections of 20 mg/kg spaced at 30, 40 and 50 min after injection of pentobarbital. Both groups were sex balanced. TRH administration resulted in dramatically increased respiration and heart rates and arrested the progress of barbiturate induced hypothermia. The extended dose schedule prolonged increased respiration rate and a differential effect of TRH on pentobarbital induced hypothermia across sexes was observed. All animals regained reflexes sooner and sleeping time was reduced by 22%. No differences in pentobarbital blood levels with TRH were observed. These results extend earlier work in rodents to primates and suggest a possible use of TRH in cases of acute barbiturate intoxication.

Effects of chlorpromazine on the vertical chamber syndrome in rhesus monkeys

In an attempt at social rehabilitation, chlorporomazine was given to three groups of rhesus monkeys that had been confined to the vertical chambers apparatus early in their development. Previous studies have shown that such periods of deprivation produce severe deficits in social behavior. There were no substantial beneficial effects of chlorpromazine treatment; however, there was a notable amount of spontaneous improvement seen in all three groups. We discuss these data in terms of their implications for the use of the vertical chamber as a tool in experimental research of psychopathological disorder.

Overview of recent research in depression. Integration of ten conceptual models into a comprehensive clinical frame

Disciplinary fragmentation and nosological and semantic controversies have obscured the impressive advances made in the area of depressive disorders during the past decade. This article is an attempt to translate data derived from psychodynamic, sociobehavioral, and neurobiologic research into a clinically meaningful framework. We review ten models of depression with special emphasis on newer models supported by empirical and experimental studies, and present a new model, which incorporates and synthesizes findings from different schools. Depressive illness is conceptualized as the feedback interaction of three sets of variables at chemical, experiential, and behavioral levels with the diencephalon serving as the field of action.

Depressive disorders: toward a unified hypothesis

Our scientific understanding of psychiatric syndromes, including the phenomena of depression, has been hampered because of: (i) the use of metapsychological concepts that are difficult to test; (ii) methodological and linguistic barriers that prevent communication among psychoanalysts, behaviorists, experimental psychologists, and psychiatrists; and (iii) the reluctance of psychiatrists to accept animal models as possible approximations of certain aspects of human psychopathology. We have attempted to demonstrate that the animal models simulate some of the central features of clinical depression (for example, helplessness and object loss), thereby allowing one to rigorously investigate them from developmental, behavioral, and biochemical perspectives. The object loss model, as a concrete version of a metapsychological-psychoanalytic concept, has enabled primatologists to study the disruption of an attachment bond. The behavioral model accommodates this concept to a broader generalization: loss of reinforcement or loss of control over reinforcement. We have reviewed the evidence that these processes involve the diencephalic centers of reward or reinforcement, thereby permitting integration of the psychoanalytical and behavioral formulations with the biochemical hypotheses. Also, we have presented data strongly suggesting that the breaking of an attachment bond in the primate represents significant loss of reinforcement that induces helplessness and disrupts motivated behavior. Finally, we have argued that the depressive syndrome could be caused by interactions of genetic, chemical, developmental, and interpersonal factors, all of which impinge on the diencephalic centers of reinforcement.