Dopaminergic activity modulation via aggression, status, and a visual social signal.

Social interaction may elicit aggression, establish social rank, and be influenced by changes in central dopaminergic activity. In the lizard Anolis carolinensis, a sign stimulus (darkening of postorbital skin or eyespots) inhibits aggressive response from opponents, in part because it forms more rapidly in dominant males. The authors report that artificially hiding or darkening eyespots influences central dopaminergic activity, social status, and aggression during dyadic social interaction. All males that viewed an opponent with eyespots painted black became subordinate and exhibited elevated dopamine in raphe, lateral amygdala, and medial amygdala but decreased dopamine in septum and locus ceruleus. In contrast, males that viewed opponents with hidden eyespots (painted green) became dominant and had increased dopamine in striatum, nucleus accumbens, hypothalamus, and combined substantia nigra/ventral tegmental area. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Links between temperamental dimensions and brain monoamines in the rat.

In 27 female Wistar rats, the authors obtained composite scores on harm avoidance and novelty seeking, as well as 57 measures of monoamines and metabolites from 10 different brain regions. A multivariate regression method was used to discover associations between individual differences in temperament and neurochemistry. Harm-avoidant subjects had low levels of striatal dopamine and high levels of cortical norepinephrine and amygdaloid 5-hydroxyindoleacetic acid. High novelty-seeking scores were linked to low levels of brainstem serotonin and dopamine and to low levels of 5-hydroxyindoleacetic acid in amygdala and accumbens. Moreover, rats scoring high on novelty seeking had higher-than-average levels of norepinephrine in the thalamus and amygdala and of serotonin in the amygdala. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Vasopressin and serotonin interactions in the control of agonistic behavior

In hamsters, dominant/subordinate relationships are initially determined by overt aggression, but subsequently communicated by flank marking, an arginine vasopressin (AVP)-dependent behavior. Once a relationship is established, dominant males will flank mark at a higher frequency than their subordinate partners. Flank marking displayed during social encounters can be turned "on or off" by microinjection of AVP or AVP-receptor antagonist within the anterior hypothalamus (AH). For instance, microinjecting dominant hamsters with AVP-receptor antagonist blocks their flank marking and provokes an immediate induction of flank marking by subordinate animals. The central effects of AVP have been extended to include a role in offensive aggression. Microinjection of AVP-receptor antagonist into the AH inhibits the aggression of a resident hamster toward an intruder and diminishes aggression between hamsters placed into a neutral arena. Microinjection of AVP into the ventrolateral hypothalamus (VLH) facilitates offensive aggression of a resident toward an intruder. As AVP receptors in the VLH are testosterone-dependent, it is possible that the reduction of aggression observed in castrated hamsters is due to a loss of AVP responsiveness in the VLH. Recent work has focused on the notion that serotonin (5-HT) antagonizes AVP activity in the CNS. The AH and VLH have a high density of 5-HT terminals and binding sites. Indeed, there appear to be 5-HT synapses on AVP neurons in the AH. Microinjection of 5-HT into the AH inhibits AVP-induced flank marking while IP injection of fluoxetine a serotonin reuptake inhibitor inhibits AVP-induced offensive aggression in the VLH. It is possible that serotonin interacts with AVP to modulate offensive aggression.     

Behavioral and neurobiological effects of estrogen replacement therapy and a history of triphasic oral contraceptive exposure

The effects of contraceptive steroids and estrogen replacement therapy on behavior and neuroendocrine function were evaluated in adult female cynomolgus monkeys. During the 'premenopausal' phase of the experiment, the animals were assigned to either treatment with a triphasic oral contraceptive (OC) for 24 months or the untreated control group. The monkeys were then ovariectomized and half of each of the premenopausal groups were randomly assigned to either treatment with conjugated equine estrogens (ERT) or the untreated control group for 12 months (the 'postmenopausal' phase). All evaluations were completed during the postmenopausal phase of the experiment. Both types of exogenous steroid treatments appeared to increase cardiovascular and hypothalamic-pituitary-adrenal responses to stress in socially dominant but not socially subordinate females. A history of triphasic OC administration increased contact aggression received, and reduced the prolactin response to fenfluramine, suggesting reduced serotonergic activity, for at least a year following the cessation of triphasic OC treatment.     

Facilitation of intermale aggression in mice through exposure to receptive females.

Examined intermale aggression after different exposures to receptive females. In Exp I, socially isolated or grouped CD-1 and Swiss-Webster mice each confronted a target male after either no exposure to or 3 intromissions with an estrous female. High levels of aggression were observed in isolated males after exposure to a female, provided the female was removed when the target male was introduced. In Exp II, variation of duration and quality of exposure to females indicated that aggression increased with more advanced prior sexual activity. In Exp III, sexual activity was not greatly influenced by prior aggressive activity. These data suggest a preparedness to fight following sexual activity, but a prepotence of sexual activity over aggression. (31 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Co-infusion with a TrkB-Fc receptor body carrier enhances BDNF distribution in the adult rat brain

Intraspecific confrontation between male rats represents a biologically relevant form of social stress. C-fos expression has been used to map the pattern of neural activation following either a single (acute) or repeated (10 times) exposure of an intruder male to a larger male in the latter's home cage. These conditions induce high levels of aggressive interaction. Sixty minutes after a single defeat, there was intense c-fos expression (quantified using image analysis) in restricted areas of the basal forebrain (including lateral septum, bed nucleus of stria terminalis, lateral preoptic area, lateral hypothalamic area, paraventricular nucleus, and medial and central amygdala) as well as in the autonomic and monoaminergic nuclei of the brainstem (central grey, dorsal and median raphe, locus coeruleus and nucleus of the solitary tract). After the tenth defeat, this pattern was modified despite persistently high levels of aggression. Some areas in the forebrain (bed nucleus of stria terminalis, paraventricular nucleus and medial amygdala) continued to express increased c-fos; others (the septum, lateral hypothalamic area, lateral preoptic area and central amygdala) no longer expressed c-fos. The brainstem response was equally varied: the central grey and the raphe nuclei continued to respond after repeated defeat, whereas the solitary nucleus and locus coeruleus did not. On the other hand, there was no change in the behaviour of intruder rats after repeated defeat. This study shows the pattern of adaptation at a cellular level in the basal forebrain and brainstem to repeated defeat. As in our previous studies of repeated restraint, modulation in the expression of c-fos following repeated stress is highly regionally specific, suggesting that differential neural processing is involved in adaptation to social stress.     

Kinship, familiarity, aggression, and dominance in deer mice (Peromyscus maniculatus) in seminatural enclosures.

This study was designed to test the effects of kinship and postweaning familiarity on male–male aggressive interactions in deer mice (Peromyscus maniculatus) in a more naturalistic situation than that of most tests of kin discrimination. Familiar males (i.e., those housed together from weaning) displayed significantly less aggression than unfamiliar males; kinship per se did not appear to affect levels of aggression. In addition, dominant males copulated more than subordinates and under some conditions sired more offspring. The posttest copulatory patterns showed that the subordinate males ejaculated after fewer intromissions than did dominant males. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effect of diazepam on voluntary ethanol intake in a rat model of alcoholism

The neuropharmacological study of serotonin and behavior has followed two fundamentally different strategies. One approach has used behavior as a dependent variable for assaying drug effects. To characterize serotonergic drugs, most studies have used relatively simple behaviors, such as locomotor activity, startle, exploration, operant responses, and sleep. A second approach has focused on behavior, with drugs used as tools to elucidate the physiological role of serotonin. These studies have increasingly focused on behaviors of ethological importance, including aggression, sexual behavior, and other forms of social interaction. Here we review studies using this approach to focus on one particular kind of social interaction: affiliation.     

Experiences of psychiatry board exam casualties: a survey report

A quantitative study of the regional distribution of serotonin (5-HT) in the forebrain, was performed in adult cats, following brainstem lesions. Seven to 10 days survival times were used to avoid nonspecific variations of the amine levels, as were observed in chronic preparations. Significant decreases of 5-HT levels were found after lesions of the nucleus centralis superior (CS), in hypothalamus, preoptic area, amygdala and hippocampus. After lesions of the nucleus dorsalis raphe (Dr), significant 5-HT decreases were also found in the hypothalamus and hippocampus. There was no change of 5-HT levels after lesions placed in the lateral midbrain, pontine tegmentum, or caudal pontine raphe, contrary to that was reported for chronic lesioned cats. These results suggest that CS and Dr may integrate different serotonergic subsystems and, probably, each one of these subsystems is related to specific functional phenomena.     

A cross-cultural comparison of behavior disturbance and suicidal behavior among psychiatrically hospitalized adolescents in Israel and the United States

This study examines sexual behavior, serotonin turnover in the central nervous system, and testosterone in free-ranging non-human primates. Study subjects were 33 young adult male rhesus macaques (Macaca mulatta) living in naturalistic social groups on a 475-acre South Carolina barrier island. Blood and cerebrospinal fluid (CSF) samples were obtained during random trappings, and the subjects were located for observation by radio telemetry. Quantitative behavioral samples totaling 203 observation hours were taken during two mating seasons (September through January) in 1994 and 1995. Control observations (65 h) on 13 subjects were also taken during the non-mating seasons in 1994 and 1995. The results indicate that CSF 5-hydroxyindoleacetic acid (5-HIAA), CSF testosterone, and plasma testosterone concentrations increase significantly during the mating season. During the mating season, there were significant increases in high intensity aggression, low intensity aggression, grooming behavior, and heterosexual mounting. In the mating season, CSF 5-HIAA was significantly correlated with several sociosexual behaviors: consorts per hour, heterosexual mounts per hour, and inseminations per hour. In contrast to previous findings from the non-mating season, CSF 5-HIAA was not correlated with any measures of aggression or sociality, although during consorting, CSF 5-HIAA was positively correlated with grooming. From these findings, we conclude that the lack of correlation between intense and severe aggression and CSF 5-HIAA in the mating season may reflect the use of high intensity aggression in 'normative' male-male competition over access to reproductively active females. We also conclude that CNS serotonin turnover is positively correlated with sexual competence, i.e. males with low CSF 5-HIAA concentrations are less sexually competent than males with higher concentrations.     

Distinct activation of monoaminergic pathways in chick brain in relation to auditory imprinting and stressful situations: a microdialysis study

In the forebrain of the domestic chick (Gallus gallus domesticus), an area termed the mediorostral neostriatum/hyperstriatum ventrale is strongly involved in emotional learning paradigms such as acoustic filial imprinting. Furthermore, the involvement of the mediorostral neostriatum/hyperstriatum ventrale in stressful situations, such as social separation, has been demonstrated in 2-deoxyglucose studies. The aim of the present study was to examine whether quantitative changes of dopamine, serotonin and their metabolites occur during auditory filial imprinting and during social separation. Using in vivo microdialysis in tone-imprinted and in naive, control chicks, we compared the extracellular levels of homovanillic acid, a metabolite of dopamine, and 5-hydroxyindoleacetic acid, a metabolite of serotonin, during the presentation of the imprinting tone. A small, but statistically significant, decrease of extracellular homovanillic acid levels was found in the mediorostral neostriatum/hyperstriatum ventrale of imprinted chicks compared to control animals, whereas changes of 5-hydroxyindoleacetic acid were not detected. In a second experiment, we investigated the levels of homovanillic acid and 5-hydroxyindoleacetic acid in the mediorostral neostriatum/hyperstriatum ventrale of socially reared chicks during different stress situations, such as handling or separation from their cage mates. Handling induced a significant increase of homovanillic acid and 5-hydroxyindoleacetic acid, while social separation resulted in a significant increase of 5-hydroxyindoleacetic acid and only a slight increase of homovanillic acid. Despite considerable inter-individual variability, the increase of distress vocalizations (duration of distress calls) after social separation displayed a good correlation to the increased 5-hydroxyindoleacetic acid levels in all animals analysed. These results provide the first evidence that the physiological response of the mediorostral neostriatum/hyperstriatum ventrale related to different emotional conditions after acoustic imprinting and during stressful situations is, at least in part, mediated by dopaminergic and/or serotonergic pathways. Furthermore, the results from the present study indicate a distinct activation of dopaminergic and serotonergic pathways in relation to the behavioural situation and the associated changes of emotional status.     

"Lesions of the dorsomedial amygdala, but not the nucleus accumbens, reduce the aversiveness of morphine withdrawal in rats": Correction.

Reports an error in the original article by J. E. Kelsey and S. R. Arnold (Behavioral Neuroscience, 1994[Dec], Vol 108[6], 1119–2127). On pages 1121 and 1122, the artwork for Figures 1 and 2 was reversed; the figure captions are correct. In the last line of the author note, on page 1119, the e-mail address should read as follows: jkelsey@bates.edu. (The following abstract of this article originally appeared in record 1995-12607-001.) Small lesions of the dorsomedial amygdala reduced the magnitude of the conditioned place aversion produced by naltrexone-precipitated morphine withdrawal, whereas large lesions of the ventral nucleus accumbens had no effect. This finding that the dorsomedial amygdala, which has not been implicated in opiate reward, is involved in mediating the aversiveness of opiate withdrawal is consistent with data indicating that amygdala lesions reduce the aversiveness of a variety of aversive events. In contrast, the nucleus accumbens, which is involved in mediating the rewarding effects of opiates, does not appear to be critically involved in mediating the aversive effects of opiate withdrawal.… (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Basolateral amygdala stimulation evokes glutamate receptor-dependent dopamine efflux in the nucleus accumbens of the anaesthetized rat

Afferents from the basolateral amygdala and dopamine projections from the ventral tegmental area to the nucleus accumbens have both been implicated in reward-related processes. The present study used in vivo chronoamperometry with stearate-graphite paste electrodes in urethane-anaesthetized rats to determine how basolateral amygdala efferents to the nucleus accumbens synaptically regulate dopamine efflux. Repetitive-pulse (20 Hz for 10 s) electrical stimulation of the basolateral amygdala evoked a complex pattern of changes in monitored dopamine oxidation currents in the nucleus accumbens related to dopamine efflux. These changes were characterized by an initial increase that was time-locked to stimulation, a secondary decrease below baseline, followed by a prolonged increase in the dopamine signal above baseline. The effects of burst-patterned stimulation (100 Hz, 5 pulses/burst, 1-s interburst interval, 40 s) of the basolateral amygdala on the basal accumbens dopamine signal were similar to those evoked by 20 Hz stimulation, with the lack of a secondary suppressive component. Infusions of the ionotropic glutamate receptor antagonists (+/-)-2-amino-5-phosphonopentanoic acid (APV) or 6,7-dinitroquinoxaline-2,3-dione (DNQX) into the nucleus accumbens dose-dependently blocked or attenuated the initial and prolonged increases in the dopamine signal following 20 Hz or burst-patterned basolateral amygdala stimulation. Infusions of the metabotropic glutamate receptor antagonist (+)-alpha-methyl-4-carboxyphenylglycine selectively blocked the intermediate suppressive effect of 20 Hz basolateral amygdala stimulation on dopamine oxidation currents. Blockade of glutamate receptors or inhibition of dopamine neuronal activity via infusions of either APV + DNQX, lidocaine or gamma-hydroxybutyric acid, respectively, into the ventral tegmental area did not effect the pattern of changes in the accumbens dopamine signal evoked by basolateral amygdala stimulation. These data suggest that the glutamatergic basolateral amygdala inputs to nucleus accumbens dopamine terminals synaptically facilitate or depress dopamine efflux, and these effects are independent of dopamine neuronal firing activity. Moreover, these results imply that changes in nucleus accumbens dopamine levels following presentation of reward-related stimuli may be mediated, in part, by the basolateral amygdala.     

Menstrual cycle and social behavior in vervet monkeys

We assessed the relationship between social behavior and the menstrual cycle in 11 adult female vervet monkeys (Cercopithecus aethiops sabaeus) living in an established, stable social group. The findings indicated that fluctuations in ovarian steroids are accompanied by behavioral changes in vervet monkeys. A significant increase in aggressive action, avoidance of social overtures, and retreats from threat occurred during the late luteal phase. However, the social environment can greatly affect behavior independent of the phase of the menstrual cycle. The 10 nondominant (or subordinate) individuals not only exhibited behavioral changes across their own menstrual cycles, but also were responsive to the dominant female's cycle. During the dominant female's late luteal phase, subordinate females significantly increased aggression and decreased social activity. Some of behavioral patterns in female vervet monkeys are therefore relatively independent of direct hormonal modulation and support the contention of the dominant female as the driving force for behavioral changes related to aggression and social interaction. The differential effect of hormones and social status and other environmental factors on behavior has not been critically evaluated in human studies of the premenstrual syndrome. The present study suggests that it is important to assess which behavioral patterns in women are hormonally mediated and which are dependent on the environment.     

Central serotonin activity and aggression: inverse relationship with prolactin response to d-fenfluramine, but not CSF 5-HIAA concentration, in human subjects

OBJECTIVE: This study compared the nature and magnitude of the relationship between aggression and CSF 5-hydroxyindoleacetic acid (5-HIAA) concentration with that between aggression and the prolactin response to d-fenfluramine challenge in human subjects. METHOD: The Life History of Aggression assessment scores of 24 subjects with personality disorders were compared with their lumbar CSF 5-HIAA concentrations and with their prolactin responses to d-fenfluramine challenge. RESULTS: Aggression was significantly and inversely correlated with prolactin responses to d-fenfluramine challenge but not with lumbar CSF 5-HIAA concentrations in these subjects. CONCLUSIONS: Prolactin response to d-fenfluramine may be more sensitive than lumbar CSF 5-HIAA concentration in detecting a relationship between aggression and central serotonin activity in noncriminally violent human subjects.     

Tumour necrosis factor-alpha and interleukin-2 differentially affect hippocampal serotonergic neurotransmission, behavioural activity, body temperature and hypothalamic-pituitary-adrenocortical axis activity in the rat

Intraperitoneal endotoxin injection and central administration of interleukin (IL)-1beta profoundly activate hippocampal serotonergic neurotransmission. This study was designed to investigate, using in vivo microdialysis, the effects of another endotoxin-induced proinflammatory cytokine, tumour necrosis factor-alpha, and the effects of the non-inflammatory cytokine, IL-2, on hippocampal extracellular levels of serotonin. To compare the effects of these cytokines on neurotransmission with the effects on physiological parameters and behaviour, hypothalamic-pituitary-adrenocortical (HPA) axis activity, body temperature and behavioural activity were monitored as well. Time-dependent changes in serotonergic neurotransmission and HPA axis activity were determined by measuring serotonin, its metabolite 5-hydroxyindoleacetic acid and free corticosterone in dialysates. Total behavioural activity was scored by assessing the time during which rats were active. Core body temperature was measured by biotelemetry. Intracerebroventricular injection of 50 or 100 ng recombinant murine tumour necrosis factor-alpha exerted no effect on hippocampal serotonergic neurotransmission, and induced no signs of sickness behaviour. However, these doses produced a dose-dependent increase in body temperature and free corticosterone levels. In contrast, intracerebroventricular administration of 500 ng, but not of 50 ng, recombinant human IL-2 produced a marked increase in hippocampal extracellular concentrations of serotonin and 5-hydroxyindoleacetic acid, accompanied by a pronounced behavioural inhibition and other signs of sickness. Moreover, both doses of IL-2 caused a dose-dependent increase in body temperature and free corticosterone levels. Interestingly, intracerebroventricular pretreatment with the IL-1 receptor antagonist showed that the effects of IL-2 on hippocampal serotonin were completely dependent on endogenous brain IL-1. However, IL-1 seemed to play only a minor role in the IL-2-induced increase in free corticosterone. Taken together, the results show that cytokines produce partially overlapping brain-mediated responses, but are selectively effective in stimulating hippocampal serotonergic neurotransmission and inducing sickness behaviour. Moreover, we postulate that activation of hippocampal serotonin release is instrumental in the full development of behavioural inhibition.     

Differences in behavioral responses to a competitive mating situation in two species of dwarf hamster (Phodopus campbelli and P. sungorus).

Social groups consisting of a female and two adult males, of two closely related species, Phodopus campbelli and P. sungorus, were observed during a 2-hr mating test. The behavioral analysis revealed (a) significant differences between the two species in the ability of the dominant male to exclude the subordinate male from mating with the estrous female and (b) significant changes in the pattern of copulation by the dominant male in response to the presence of a second male even when the second male was not mating with the female. Dominant male P. sungorus were always successful in preventing subordinate males from mating. In contrast, subordinate male P. campbelli mated with the female in 6 of 12 groups in spite of high levels of aggression and the potential for serious injury. When both P. campbelli males mated, dominant males ejaculated first and most frequently. The response to the presence of a second male in P. sungorus included an accelerated copulatory pattern, with decreased durations of individual ejaculatory series and postejaculatory refractory periods. This resulted in an average of one extra ejaculation during the first hour of testing. The temporal pattern of mating in P. campbelli was not accelerated by the presence of a second male, but the intromission/mount ratio was increased significantly, and the duration of the ejaculatory lock decreased. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Timing of computed tomography in acute diverticulitis

OBJECTIVE: Studies on brain serotonin metabolism in human and nonhuman primates have indicated that dysfunction of serotonin transmission may play a role in the biological vulnerability to dependence on alcohol. Among young men, low sensitivity to alcohol intoxication predicts subsequent alcohol abuse and dependence. METHOD: The authors used single photon emission computed tomography and the radioligand [(I)123]beta-CIT ([(I)123]methyl 3beta-(4-iodophenyl) tropane-2-carboxylate) to measure the availability of serotonin transporters in 11 male rhesus monkeys, and the monkeys were genotyped for a functional polymorphism of the serotonin transporter gene. The 11 monkeys had experienced parental separation after birth; their behavior and 5-hydroxyindoleacetic acid (5-HIAA) concentrations in CSF had been assessed regularly. RESULTS: In the 5-year-old monkeys, there was a significant negative correlation between beta-CIT binding to serotonin transporters in the brainstem and 5-HIAA concentrations in CSF. Animals with greater beta-CIT binding and low CSF 5-HIAA concentrations displayed greater aggressiveness and were less sensitive to alcohol-induced intoxication. The genetic constitution of the serotonin transporter promoter gene did not significantly contribute to the availability of brainstem serotonin transporters as measured by beta-CIT binding. CONCLUSIONS: In adult nonhuman primates who underwent early developmental stress, variables indicating a low serotonin turnover rate were associated with behavior patterns similar to those predisposing to early-onset alcoholism among humans.     

Moving beyond fear: lessons learned through a longitudinal review of the literature regarding health care providers and the care of people with HIV/AIDS

Exposure to hostile conditions initiates the secretion of several hormones, including corticosterone/cortisol, catecholamines, prolactin, oxytocin, and renin, as part of the survival mechanism. Such conditions are often referred to as "stressors" and can be divided into three categories: external conditions resulting in pain or discomfort, internal homeostatic disturbances, and learned or associative responses to the perception of impending endangerment, pain, or discomfort ("psychological stress"). The hormones released in response to stressors often are referred to as "stress hormones" and their secretion is regulated by neural circuits impinging on hypothalamic neurons that are the final output toward the pituitary gland and the kidneys. This review discusses the forebrain circuits that mediate the neuroendocrine responses to stressors and emphasizes those neuroendocrine systems that have previously received little attention as stress-sensitive hormones: renin, oxytocin, and prolactin. Anxiolytic drugs of the benzodiazepine class and other drugs that affect catecholamine, GABAA, histamine, and serotonin receptors alter the neuroendocrine stress response. The effects of these drugs are discussed in relation to their effects on forebrain neural circuits that regulate stress hormone secretion. For psychological stressors such as conditioned fear, the neural circuits mediating neuroendocrine responses involve cortical activation of the basolateral amygdala, which in turn activates the central nucleus of the amygdala. The central amygdala then activates hypothalamic neurons directly, indirectly through the bed nucleus of the stria terminalis, and/or possibly via circuits involving brainstem serotonergic and catecholaminergic neurons. The renin response to psychological stress, in contrast to those of ACTH and prolactin, is not mediated by the bed nucleus of the stria terminalis and is not suppressed by benzodiazepine anxiolytics. Stressors that challenge cardiovascular homeostasis, such as hemorrhage, trigger a pattern of neuroendocrine responses that is similar to that observed in response to psychological stressors. These neuroendocrine responses are initiated by afferent signals from cardiovascular receptors which synapse in the medulla oblongata and are relayed either directly or indirectly to hypothalamic neurons controlling ACTH, prolactin, and oxytocin release. In contrast, forebrain pathways may not be essential for the renin response to hemorrhage. Thus current evidence indicates that although a diverse group of stressors initiate similar increases in ACTH, renin, prolactin, and oxytocin, the specific neural circuits and neurotransmitter systems involved in these responses differ for each neuroendocrine system and stressor category.     

Efficacy of taxol in the orpk mouse model of polycystic kidney disease

Studies on conscious Sprague-Dawley rats using intracerebral dialysis in live animals combined with high-performance liquid chromatography with electrochemical detection showed that administration of apomorphine into the nucleus accumbens decreased the levels of dihydroxyphenylacetic acid and 5-hydroxyindoleacetic acid in the extracellular space of the dorsal striatum throughout the observation period and produced a transient reduction in the level of homovanillic acid in the dialysate from this structure. The studies demonstrated that reversible exclusion of the nucleus accumbens with procaine produced a transient increase in the levels of dopamine metabolites, without an increase in serotonin metabolites, in the extracellular space of the dorsal striatum. These results demonstrate that the nucleus accumbens affects dopamine metabolism in the striatum, this being mediated by the dopamine-reactive system in the nucleus accumbens.