Implementation of Photon Treatment Back-Up Workflow at a High-Volume Proton Center: Safety, Quality, and Patient Considerations

A successful proton beam therapy (PBT) center relies heavily on the proper function and maintenance of a proton beam therapy machine. However, when a PBT machine is non-operational, a proton facility is hindered with delays that can potentially lead to inferior treatment outcome due to treatment interruption. The implementation of a workflow for which proton plans are converted to photon plans so that patients can be treated using photon has been a successful strategy to reduce delays and mitigate its impact on patient care. This workflow was established through collaboration of physicians, physicists, dosimetrists, therapists, nurses, and schedulers. A tiered system established by disease site, number of fractions, and individualized circumstances is used to prioritize patients. This article provides an overview of workflow of conversion of PBT to photon when the PBT machine is down. Specific needs of patients undergoing proton beam therapy are addressed.

Small-spot intensity-modulated proton therapy and volumetric-modulated arc therapies for patients with locally advanced non-small-cell lung cancer: A dosimetric comparative study

Purpose

To compare dosimetric performance of volumetric‐modulated arc therapy (VMAT) and small‐spot intensity‐modulated proton therapy for stage III non‐small‐cell lung cancer (NSCLC).

Methods and Materials

A total of 24 NSCLC patients were retrospectively reviewed; 12 patients received intensity‐modulated proton therapy (IMPT) and the remaining 12 received VMAT. Both plans were generated by delivering prescription doses to clinical target volumes (CTV) on averaged 4D‐CTs. The dose‐volume‐histograms (DVH) band method was used to quantify plan robustness. Software was developed to evaluate interplay effects with randomized starting phases of each field per fraction. DVH indices were compared using Wilcoxon rank sum test.

Results

Compared with VMAT, IMPT delivered significantly lower cord D_max, heart D_mean, and lung V_5 Gy[RBE] with comparable CTV dose homogeneity, and protection of other OARs. In terms of plan robustness, the IMPT plans were statistically better than VMAT plans in heart D_mean, but were statistically worse in CTV dose coverage, cord D_max, lung D_mean, and V_5 Gy[RBE]. Other DVH indices were comparable. The IMPT plans still met the standard clinical requirements with interplay effects considered.

Conclusions

Small‐spot IMPT improves cord, heart, and lung sparing compared to VMAT and achieves clinically acceptable plan robustness at least for the patients included in this study with motion amplitude less than 11 mm. Our study supports the usage of IMPT to treat some lung cancer patients.

The role of oxytocin in male and female reproductive behavior

Oxytocin (OT) is a nonapeptide with an impressive variety of physiological functions. Among them, the 'prosocial' effects have been discussed in several recent reviews, but the direct effects on male and female sexual behavior did receive much less attention so far. As our contribution to honor the lifelong interest of Berend Olivier in the control mechanisms of sexual behavior, we decided to explore the role of OT in the present review. In the successive sections, some physiological mechanisms and the 'pair-bonding' effects of OT will be discussed, followed by sections about desire, female appetitive and copulatory behavior, including lordosis and orgasm. At the male side, the effects on erection and ejaculation are reviewed, followed by a section about 'premature ejaculation' and a possible role of OT in its treatment. In addition to OT, serotonin receives some attention as one of the main mechanisms controlling the effects of OT. In the succeeding sections, the importance of OT for 'the fruits of labor' is discussed, as it plays an important role in both maternal and paternal behavior. Finally, we pay attention to an intriguing brain area, the ventrolateral part of the ventromedial hypothalamic nucleus (VMHvl), apparently functioning in both sexual and aggressive behavior, which are at first view completely opposite behavioral systems.

Stress revisited: a critical evaluation of the stress concept

With the steadily increasing number of publications in the field of stress research it has become evident that the conventional usage of the stress concept bears considerable problems. The use of the term 'stress' to conditions ranging from even the mildest challenging stimulation to severely aversive conditions, is in our view inappropriate. Review of the literature reveals that the physiological 'stress' response to appetitive, rewarding stimuli that are often not considered to be stressors can be as large as the response to negative stimuli. Analysis of the physiological response during exercise supports the view that the magnitude of the neuroendocrine response reflects the metabolic and physiological demands required for behavioural activity. We propose that the term 'stress' should be restricted to conditions where an environmental demand exceeds the natural regulatory capacity of an organism, in particular situations that include unpredictability and uncontrollability. Physiologically, stress seems to be characterized by either the absence of an anticipatory response (unpredictable) or a reduced recovery (uncontrollable) of the neuroendocrine reaction. The consequences of this restricted definition for stress research and the interpretation of results in terms of the adaptive and/or maladaptive nature of the response are discussed.

The potential and limitations of DOV 216,303 as a triple reuptake inhibitor for the treatment of major depression: a microdialysis study in olfactory bulbectomized rats

DOV 216,303 belongs to a new class of antidepressants, the triple reuptake inhibitors (TRIs), that blocks serotonin, norepinephrine and dopamine transporters and thereby increases extracellular brain monoamine concentrations. The aim of the present study was to measure extracellular monoamine concentrations both in the prefrontal cortex (PFC) and dorsal hippocampus (DH) after chronic administration of DOV 216,303 in the OBX animal model of depression and to compare the effects with acute drug treatment. OBX animals showed lower dopamine levels in PFC upon acute administration of DOV 216,303 than sham animals for up to five weeks after surgery. No such changes were observed in the DH. Unexpectedly, a DOV 216,303 challenge in chronic DOV 216,303 treated sham animals resulted in a blunted dopamine response in the PFC compared to the same challenge in vehicle treated animals. This blunted response probably reflects pharmacokinetic adaptations and/or pharmacodynamic changes, since brain and plasma concentrations of DOV 216,303 were significantly lower after chronic administration compared to acute administration. Surprisingly, and in contrast what we have reported earlier, chronic DOV 216,303 treatment was unable to normalize the hyperactivity of the OBX animals. Interestingly, by measuring the drug plasma and brain levels, it was demonstrated that at the time of behavioral testing (24 h after last drug treatment) DOV 216,303 was not present anymore in either plasma or brain. This seems to indicate that this putative antidepressant drug has no lasting antidepressant-like behavioral effects in the absence of the drug in the brain.

The effects of acute tryptophan depletion on affective behaviour and cognition in Brown Norway and Sprague Dawley rats

Previous studies in rats and humans have shown that the essential amino acid tryptophan (TRP) is depleted after consumption of a gelatin-based protein-carbohydrate mixture, which is lacking L-tryptophan (TRP-). In rats, TRP depletion caused impaired object recognition but only had a modest effect on affective behaviour. Because these studies were preformed with Wistar rats, the aim of the present experiment was to evaluate strain differences in behavioural responses to acute TRP depletion between Brown Norway (BN) and Sprague Dawley (SD) rats. The rats were repeatedly treated with TRP- or a balanced control (TRP+) and were tested in tests of anxiety- and depression-related behaviour (open-field test, home cage emergence test, social interaction test, forced swim test) and memory. SD rats, but not BNs, showed more anxiety- and depression-related behaviour and impaired object recognition after TRP- treatment. There was a dissociation between plasma TRP levels, central 5-HT concentrations and 5-HIAA/5-HT turnover. Both strains showed about 60% decrease in plasma TRP/SigmaLNAA levels, whereas hippocampal 5-HT levels were lower after TRP- in BN but not SD rats. Conversely, 5-HIAA/5-HT turnover was lower after TRP- in SD but not BN rats, suggesting a dissociation between 5-HT storage and release in SDs. The present study suggests that acute tryptophan depletion effects are strain dependent on the behavioural and the neurochemical level.

Acute tryptophan depletion dose dependently impairs object memory in serotonin transporter knockout rats

RATIONALE

Acute tryptophan depletion (ATD) transiently lowers central serotonin levels and can induce depressive mood states and cognitive defects. Previous studies have shown that ATD impairs object recognition in rats.

OBJECTIVES

As individual differences exist in central serotonin neurotransmission, the impact of ATD may vary accordingly. In this experiment, we investigated the hypothesis that male serotonin transporter knockout (SERT(-/-)), rats marked by a lower SERT function, are more vulnerable to the effects of ATD in an object recognition task than male wildtype (SERT(+/+)) and heterozygous (SERT(+/-)) rats.

MATERIALS AND METHODS

Twelve male SERT(+/+), SERT(+/-), and SERT(-/-) rats were treated with standard dose and low-dose ATD using a gelatine-based protein-carbohydrate mixture lacking tryptophan. In the control treatment, L: -tryptophan was added to the mixture. Four hours after treatment, the rats were subjected to the object recognition task. In addition, the effects of ATD on plasma amino acid concentrations were measured, and concentrations of 5-HT and 5-HIAA were measured in the frontal cortex and hippocampus of these rats.

RESULTS

Plasma TRP levels and central 5-HT and 5-HIAA levels were decreased in all genotypes after ATD, but effects were stronger in SERT(-/-) rats. The standard dose of ATD impaired object recognition in all genotypes. SERT(-/-) and SERT(+/-) rats were more vulnerable to low dose of ATD in the object recognition task compared to SERT(+/+) rats.

CONCLUSIONS

These results indicate a greater sensitivity to ATD in SERT(-/-) and SERT(+/-) rats, which may be related to stronger central depletion effects in these rats.

Repeated social defeat in female pigs does not induce neuroendocrine symptoms of depression, but behavioral adaptation

The aim of this study was to develop an animal model of major depression. Since two thirds of depressive patients are women, it is important to develop specific female animal models of depression. We therefore determined the consequences of chronic social defeat in individually housed prepubertal female pigs confronted with a dominant, older pig. Repeated defeat increased the salivary cortisol level, measured immediately after the confrontations, but this effect diminished after repeated confrontations. Neither organ weights nor the number of glucocorticoid (GR) and mineralocorticoid (MR) receptors in the ventral hippocampus were affected by repeated defeat. Serotonin turnover in the dorsal hippocampus was also unaffected. Behavioral analysis revealed that across confrontations, the pigs reduced the time spent actively attacking the dominant pigs, whereas the time increased in which the pigs passively underwent aggression and/or actively avoided aggression. Therefore, we conclude that the repeated social defeat paradigm does not induce long-lasting depression-like neuroendocrine effects as a consequence of behavioral adaptations (changes in the fighting strategy) in the young female pigs.

Treatment planning for dose escalation in non-small cell lung cancer (NSCLC)

This study was performed to examine potential field arrangements for irradiating non-small cell lung cancer (NSCLC) on a dose escalation study. An example patient was chosen and 7 coplanar treatment plans were created to treat a NSCLC. Two plans included prophylactic nodal irradiation (PNRT) and 5 did not. Four plans used 4 fields, 2 plans used 5 fields, and 1 plan included dynamic conformal 360 degrees rotational therapy. All plans delivered 80 Gy to the isocenter with 10-MV x-rays. Each plan was initially created without dose inhomogeneity corrections and then was recalculated with these corrections, maintaining the same weighting and number of monitor units. Avoiding PNRT spared a considerable volume of normal tissue from radiation. Plans with 5 fields generally spared normal tissues better than 4-field plans. There was no benefit to the dynamic conformal 360 degrees rotational plan. Inhomogeneity corrections revealed that higher doses were delivered to both the tumor and normal structures. Seven beam arrangements for the treatment of NSCLC were compared to develop potential beam arrangements that would be applicable to treating NSCLC on a multi-institutional dose escalation study. We favor the use of at least 5 beams in most situations. It is possible that the use of more fields would further improve plans up to a point of diminishing returns, as exemplified by the lack of benefit seen with the dynamic conformal 360 degrees rotational plan. It is possible that the use of noncoplanar fields or intensity-modulated radiation therapy (IMRT) may further improve the therapeutic ratio.

Mapping quantitative trait loci affecting feather pecking behavior and stress response in laying hens

In the European Union, legislation concerning animal housing is becoming stricter because of animal welfare concerns. Feather pecking (FP) in large group housing systems is a major problem. It has been suggested that corticosterone (CORT) response to manual restraint as a measure for stress is associated with FP behavior. The aim of the current study was to identify QTL involved in FP behavior and stress response in laying hens. An F2 population of 630 hens was established from a cross between two commercial lines of laying hens differing in their propensity to feather peck. The behavioral traits, measured at 6 and 30 wk of age, were gentle FP, severe FP, and aggressive pecking. Toe pecking was measured at 30 wk of age and CORT response to manual restraint was measured at 32 wk. All animals were genotyped for 180 microsatellite markers. A QTL analysis was performed using a regression interval mapping method. At 6 wk of age, a suggestive QTL on GGA10 was detected for gentle FP. At 30 wk of age, suggestive QTL were detected on GGA1 and GGA2 for gentle FP. A significant QTL was detected on GGA2 for severe FP. At 32 wk of age, a suggestive QTL was detected on GGA18 for CORT response to manual restraint. In addition, a suggestive QTL was detected on GGA5 with possible maternal parent-of-origin effect for CORT response.

Stress responses during milking; comparing conventional and automatic milking in primiparous dairy cows

A comparative study was performed to evaluate the differences in behavioral and physiological stress responses during milking between cows that were milked by an automated milking system (AM-cows) and cows that were milked in a conventional tandem parlor (TM-cows). In a randomized design, 36 primiparous Holstein-Friesian dairy cows were observed and blood sampled (1-min intervals) individually during milking. AM-cows spent less time standing with their heads outside the feeding trough than TM-cows and had a lower heart rate. In addition, AM-cows had lower maximum plasma adrenaline and noradrenaline concentrations during milking. No differences were found in the number of steps. After tactile stimulation of the teats either by hand or by the cleaning brush, mean oxytocin concentrations did not differ. In AM-cows, however, elevated oxytocin levels were prolonged at the end of milking. Averaged over the first five blood samples, AM-cows tended to have higher plasma cortisol concentrations than TM-cows, but median fecal concentrations of the cortisol metabolite dioxoandrostane were comparable. Maximum quarter milk flow, maximum udder milk flow and residual milk as a percentage of the total milk volume was comparable. From this study it is concluded that behavioral and physiological responses, both in automatically and in conventionally milked cows, were relatively low and were typical for cows being milked. We therefore conclude that, as far as the welfare of the dairy cow during milking is concerned, automatic milking and conventional milking are equally acceptable.

Corticosteroids in relation to fear, anxiety and psychopathology

Corticosteroids play extremely important roles in fear and anxiety. The mechanisms by which corticosteroids exert their effects on behavior are often indirect, because, although corticosteroids do not regulate behavior, they induce chemical changes in particular sets of neurons making certain behavioral outcomes more likely in certain contexts as a result of the strengthening or weakening of particular neural pathways. The timing of corticosteroid increase (before, during or after exposure to a stressor) determines whether and how behavior is affected. The present review shows that different aspects of fear and anxiety are affected differentially by the occupation of the mineralocorticoid receptor (MR) or glucocorticoid receptor (GR) at different phases of the stress response. Corticosteroids, at low circulating levels, exert a permissive action via brain MRs on the mediation of acute freezing behavior and acute fear-related plus-maze behavior. Corticosteroids, at high circulating levels, enhance acquisition, conditioning and consolidation of an inescapable stressful experience via GR-mechanisms. Brain GR-occupation also promotes processes underlying fear potentiation. Fear potentiation can be seen as an adjustment in anticipation of changing demands. However, such feed-forward regulation may be particularly vulnerable to dysfunction. MR and/or GR mechanisms are involved in fear extinction. Brain MRs may be involved in the extinction of passive avoidance, and GRs may be involved in mediating the extinction of active avoidance. In the developing brain, corticosteroids play a facilitatory role in the ontogeny of freezing behavior, probably via GRs in the dorsal hippocampus, and their influence on the development of the septo-hippocampal cholinergic system. Corticosteroids can exert maladaptive rather than adaptive effects when their actions via MRs and GRs are chronically unbalanced due to chronic stress. Both mental health of humans and animal welfare is likely to be seriously threatened after psychosocial stress, prolonged stress, prenatal stress or postnatal stress, especially when maternal care or social support is absent, because these can chronically dysregulate the central MR/GR balance. In such circumstances the normally adaptive corticosteroid responses can become maladaptive.

Farm animal welfare research in interaction with society

Over the last 30 years concern about farm animal welfare has increased and has become a public issue in the Netherlands. Public discussion has stimulated research in this field, financed by both government and industry. Dutch society in general and consumers of animal products in particular, want to see high standards of welfare for production animals. Good animal welfare has gradually gained more impact in the total quality concept of the product. This will encourage scientists to continue to analyse the welfare status of animals and to come up with innovative solutions for the remaining problems. At ID-Lelystad much effort is put into farm animal welfare research. This research includes for example, the development of behavioural tests for quantifying and interpreting fear in cattle, investigations into the effects of dietary iron supply and a lack of roughage on behaviour, immunology, stress physiology, and pathology in veal calves, studies of the ontogeny of tail biting in finishing pigs and feather pecking in laying hens as well as evaluation of the welfare effects of automatic milking in dairy cows. The results of these projects contribute to concrete improvements in animal husbandry and expertise and support policy making and legislation. The animal industry as well as retailers should aim at the further implementation of this knowledge and to specify welfare standards to guarantee consumer acceptance of animal production.

The amount of free corticosterone is increased during lipopolysaccharide-induced fever

The relation between lipopolysaccharide (LPS)-induced fever and bioavailability of corticosterone (B) was examined in male Wistar rats. Animals were injected with LPS (2.5 mg/kg i.p.) or saline and core temperature and heart rate were monitored continuously using a biotelemetry system. Blood samples were withdrawn from freely moving rats via jugular catheters for estimation of total and free plasma B. LPS induced a long-lasting increase (24-48 h) in core temperature and B secretion and a short-lasting increase (90 min) in heart rate. LPS-induced fever was accompanied by a significant increase in the free/total B ratio. In contrast, an acute injection of B, which resulted in circulating B levels similar to those found after LPS, did not affect the free/total B ratio. The important role of LPS-induced fever in the hormone secretion pattern and the equilibrium between free and total B was further demonstrated in an in vitro study showing that an increase in the temperature by 3 degrees C elevated the free B fraction and the free/total B ratio of plasma samples with concentrations of B in the physiological range (5-40 microg/dl). Taken together, these findings indicate that during LPS-induced fever there is an increase in the amount of biologically available B. Exposure of glucocorticoid-sensitive targets to elevated levels of free B could contribute to the restoration of homeostasis that is disturbed during inflammation.

Effects of environmental enrichment on behavioral responses to novelty, learning, and memory, and the circadian rhythm in cortisol in growing pigs

Previously we showed that pigs reared in an enriched environment had higher baseline salivary cortisol concentrations during the light period than pigs reared under barren conditions. In the present experiment, it was investigated whether these higher baseline salivary cortisol concentrations were a real difference in cortisol concentration or merely represented a phase difference in circadian rhythm. The effects of different cortisol concentrations on the behavioral responses to novelty and learning and long-term memory in a maze test were also studied in enriched and barren housed pigs. At 9 weeks of age enriched and barren housed pigs did not differ in baseline salivary cortisol concentrations nor in circadian rhythm, but at 22 weeks of age barren housed pigs had a blunted circadian rhythm in salivary cortisol as compared to enriched housed pigs. The differences in baseline salivary cortisol concentrations between enriched- and barren-housed pigs are age-dependent, and become visible after 15 weeks of age. Enriched- and barren-housed piglets did not differ in time spent on exploration in the novel environment test. Barren-housed pigs had an impaired long-term memory in the maze test compared to enriched-housed pigs; however, no differences in learning abilities between enriched- and barren-housed pigs were found. Because blunted circadian cortisol rhythms are often recorded during states of chronic stress in pigs and rats or during depression in humans, it is suggested that the blunted circadian rhythm in cortisol in barren-housed pigs similarily may reflect decreased welfare.

Coping styles in animals: current status in behavior and stress-physiology

This paper summarizes the current views on coping styles as a useful concept in understanding individual adaptive capacity and vulnerability to stress-related disease. Studies in feral populations indicate the existence of a proactive and a reactive coping style. These coping styles seem to play a role in the population ecology of the species. Despite domestication, genetic selection and inbreeding, the same coping styles can, to some extent, also be observed in laboratory and farm animals. Coping styles are characterized by consistent behavioral and neuroendocrine characteristics, some of which seem to be causally linked to each other. Evidence is accumulating that the two coping styles might explain a differential vulnerability to stress mediated disease due to the differential adaptive value of the two coping styles and the accompanying neuroendocrine differentiation.

Y chromosomal and sex effects on the behavioral stress response in the defensive burying test in wild house mice

Genetically selected short attack latency (SAL) and long attack latency (LAL) male wild house mice behave differently in the defensive burying test. When challenged, SAL males respond actively with more time spent on defensive burying, whereas LAL males are more passive with more time remaining immobile. The first aim of this study was to find out whether the nonpairing part of the Y chromosome (Y(NPAR)) affects the behavioral stress response in this paradigm. Second, to determine if the differential behavioral profile found in males is also present in females, SAL and LAL females were tested. Third, nonattacking and attacking LAL males were compared. Five behavioral elements were recorded: defensive burying, immobility, rearing, grooming, and exploration. Males were first tested for attack latency. The results show that the Y(NPAR) influences defensive burying. However, the size of this effect is overshadowed by the background of the mice. Furthermore, although females differed from males, they tended to demonstrate the same behavioral profile as males. Nongenetic factors may also play a role, as attacking LAL males showed more defensive burying than nonattacking LAL males.

Fear-potentiation in the elevated plus-maze test depends on stressor controllability and fear conditioning

The purpose of the study was to determine which stressor qualities (escapable vs. inescapable stress and unconditioned vs. conditioned stress) can potentiate fear in the elevated plus-maze. While inescapable stress potentiated fear, escapable stress did not, but escapable stress increased the locomotor activity (closed arm entries). Inescapable stress only potentiated fear when re-exposure to the former shock compartment, 24 h after footshock and without further footshock, took place just before to 90 min before testing in the elevated plus-maze. We conclude that fear-potentiation in the plus-maze depends on stressor controllability and contextual conditioning. Fear-potentiation was reduced by the anxiolytic diazepam (0.5, 1.0 and 2.0 mg/kg, s.c.) and was further enhanced by the anxiogenic DMCM (1.0 mg/kg, s.c). The fear-potentiated plus-maze test may be a valuable tool in the search for novel anxiolytics and in the study of the neurobiology of fear-potentiation, fear conditioning and generalization of fear.

High carbon dioxide tension (PCO2) and the incidence of cardiac arrhythmias in rapidly growing broiler chickens

The purpose of this investigation was to determine whether two-week-old rapidly growing broiler chickens with high metabolic activity have an increased risk of the development of heart failure three to five weeks later. The incidence of cardiac arrhythmias was assessed in broiler chickens with either a relatively high carbon dioxide tension (PCO2) or a low PCO2 in their venous blood. Their electrocardiograms (ECGS) were measured when the birds were between five and seven weeks old by means of a biotransplant which allowed them to move freely. Premature ventricular beats were observed in all the birds, but the largest numbers were observed in birds that had had a high PCO2 when they were two weeks old.

Corticosterone modifies muscarinic receptor immunoreactivity in rat hippocampus

In the present study we report the effect of corticosterone in the regulation of hippocampal muscarinic acetylcholine receptor immunoreactivity (mAChR-ir) expression in rats. Adrenalectomy (ADX) or a single injection of a mineralocorticoid antagonist RU-28318 (1.0 mg/100 g body weight (b.w.)) in adrenally intact rats 24 h prior to sacrifice revealed an increased mAChR-ir in hippocampal CA1 and CA3 areas. Corticosterone replacement (100 microg/100 g b.w.) prevented the increase in mAChR-ir of ADX animals. However, glucocorticoid receptor antagonist (RU38486) treatment in adrenally intact rats failed to affect the mAChR immunolabeling. These results point to a modulation of muscarinic receptors by corticosterone that is predominantly mediated by the mineralocorticoid receptor.

Housing familiar male wildtype rats together reduces the long-term adverse behavioural and physiological effects of social defeat

Social stress in rats is known to induce long-lasting, adverse changes in behaviour and physiology, which seem to resemble certain human psychopathologies, such as depression and anxiety. The present experiment was designed to assess the influence of individual or group housing on the vulnerability of male Wildtype rats to long-term effects of inescapable social defeat. Group-housed rats were individually exposed to an aggressive, unfamiliar male conspecific, resulting in a social defeat. Defeated rats were then either individually housed or returned to their group. The changes in their behaviour and physiology were then studied for 3 weeks. Results showed that individually housed rats developed long-lasting, adverse behavioural and physiological changes after social defeat. Their body growth was significantly retarded (p < .05) between 7 and 14 days after defeat. When individually and group-housed rats were exposed to a mild stressor (sudden silence) 2 days after defeat, both groups became highly immobile. However, when exposure was repeated at day 21, individually housed rats were still highly immobile compared to group-housed rats which regained their normal mobility after only 7 days. In an open field test, also regularly repeated, individually housed rats took significantly longer to leave their home base and were also significantly less mobile than group-housed rats over the entire 3-week test period as well as at specific timepoints. When the rats were placed in an elevated plus-maze 14 days after defeat, those that were individually housed were significantly more anxious than those that were group-housed. When tested at 21 days after defeat in a combined dexamethasone (DEX)/corticotrophin-releasing factor (CRF) test, results showed that the hypothalamic-pituitary-adrenocortical (HPA) activity in individually housed rats was higher. This was evidenced in the latter animals by the fact that DEX was significantly less able to suppress the secretion of ACTH and corticosterone, and by a significantly higher release of ACTH after administration of CRF. Although the weights of the spleen and testes of the two groups did not differ, the adrenals of individually housed rats were larger and the thymus and seminal vesicles were smaller. We conclude that when rats are isolated after defeat, they show long-lasting, adverse behavioural and physiological changes that resemble symptoms of stress-related disorders. In contrast, when familiar rats are housed together these effects of a social defeat are greatly reduced. These findings show that housing conditions importantly influence the probability of long-term adverse behavioural and physiological effects of social defeat in male Wildtype rats.

Heart rate variability during manual restraint in chicks from high- and low-feather pecking lines of laying hens

The purpose of this investigation was to determine whether there is a difference in coping style in chicks from a high (HFP)- and low-feather pecking (HFP) line of laying hens. Active and passive coping styles can be distinguished by differences in sympathetic and parasympathetic activities on the heart. We studied heart rate during baseline conditions and during manual restraint in HFP and LFP hens. Heart rate and locomotor activity were successfully monitored around the clock with a biotelemetric implant. During the light period, the values for locomotor activity and heart rate were highest, whereas during the dark period they were the lowest. These values did not differ in LFP and HFP hens. However, during manual restraint (restraining the bird on its side by hand for 8 min) HFP birds had somewhat faster heart rate than LFP birds (at 4 min, p = 0.066). Studying heart rate variability during manual restraint showed that LFP chickens had a significant higher parasympathetic activity at 5 min (p = 0.023) and at 6 min (p = 0.002) as compared to HFP hens. The results showed that in terms of coping style, LFP chickens are passive, whereas HFP birds are active.

Neuroprotection against N-methyl-D-aspartate-induced excitotoxicity in rat magnocellular nucleus basalis by the 5-HT1A receptor agonist 8-OH-DPAT

The present study reports the neuroprotective efficacy of the 5-HT1A receptor agonists 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) and ipsapirone against in vivo excitotoxic neuronal injury. Excitotoxic cell death was induced by injections of N-methyl-D-aspartate (NMDA) in the rat magnocellular nucleus basalis. The neurodegenerative effects were quantified by image analysis of the axonal density of the nucleus basalis projection to the somatosensory cortex visualized with acetylcholinesterase histochemistry. Pretreatment with 8-OH-DPAT--but not ipsapirone--1 h prior to NMDA infusion showed significant preservation of cortical cholinergic innervation in all doses tested. Furthermore, 8-OH-DPAT exhibited sustained efficacy under homeothermic conditions in which the body temperature was maintained at 36.8 +/- 0.1 degrees C. These data indicate that selective 5-HT1A receptor activation by 8-OH-DPAT protects against NMDA-induced excitotoxic neuronal damage, probably as a result of 5-HT1A receptor-mediated neuronal hyperpolarization.

Effects of strawbedding on physiological responses to stressors and behavior in growing pigs

To study the effects of environmental enrichment on physiological responses to stressors and behavior in growing pigs, pigs were housed in either a poor environment (standard farrowing pens followed by standard rearing and fattening pens) or in an enriched environment (larger farrowing pens followed by larger rearing and fattening pens, provision of straw). Body temperature, heart rate and salivary cortisol were measured during baseline conditions and in response to relocation, isolation and restraint. Pigs housed in the poor environment performed more manipulative social behavior directed to penmates than pigs housed in the enriched environment. Physiological responses to the stressors were the same for enriched- and poor-housed pigs. Surprisingly, enriched-housed pigs had significantly higher baseline salivary cortisol concentrations, especially at 14 and 17 weeks of age. Moreover, enriched housed pigs had a lower baseline body temperature at 17 weeks of age. Thus, provision of straw has an effect on behavior, baseline HPA-axis activity and baseline body temperature in growing pigs.

Repeated blockade of mineralocorticoid receptors, but not of glucocorticoid receptors impairs food rewarded spatial learning

Corticosteroids from the adrenal cortex influence a variety of behaviours including cognition, learning and memory. These hormones act via two intracellular receptors, the mineralo-corticoid receptor (MR) and the glucocorticoid receptor (GR). These two receptor types display a high concentration and distinct distribution in the hippocampus, a brain region which is directly involved in the regulation of spatial orientation and learning. In this study, repeated subcutaneous administration of the mineralocorticoid receptor antagonist RU28318 (1.0 mg/100 g body weight), the glucocorticoid receptor blocker RU38486 (2.5 mg/100 g body weight), or a combination of both antagonists were investigated for their effects on working--and reference memory in morning and afternoon trials during 8 subsequent days in food rewarded spatial learning in a hole board task. Each rat received one dose of either vehicle (2% ethanol in PEG 400), RU28318, RU38486 or the combination of both antagonists directly after the first trial on training days 1, 3, 5, and 7. The experiments demonstrated that repeated blockade of mineralocorticoid receptors impairs reference memory reflected in the morning--as well as in the afternoon trial, whereas blockade of glucocorticoid receptors has little effect on this type of cognitive behaviour. Furthermore, combined blockade of MRs and GRs resulted in a decrease, in both daily trials, in reference memory as well as working memory performance. These findings suggest that in this spatial learning paradigm, the impairment of working memory required blockade of both receptor types, while reference memory performance involves predominantly the mineralocorticoid receptors.

Plasma catecholamine and corticosterone levels during manual restraint in chicks from a high and low feather pecking line of laying hens

Neurosympathetic and adrenal responsivity to manual restraint was studied in two White Leghorn chicken lines which differ in their tendency to feather peck. Blood samples were taken from freely moving cannulated birds during resting conditions and during manual restraint (placing the bird on its side for 8 min) to determine plasma noradrenaline. adrenaline and corticosterone. Plasma corticosterone levels in low feather peckers (LFP) were significantly higher during resting conditions and restraint as compared to the high feather peckers (HFP). In response to manual restraint the HFP hens showed a significantly larger plasma noradrenaline response than LFP hens. No difference in plasma adrenaline levels was observed under resting conditions or during manual restraint.

Blockade of corticosterone synthesis reduces serotonin turnover in the dorsal hippocampus of the rat as measured by microdialysis

The influence of plasma corticosterone concentration on serotonin (5-HT) turnover in the dorsal hippocampus was investigated. The experiments were performed in freely moving male Wistar rats in their home cage. Blood samples were taken via a permanent jugular vein catheter to determine plasma corticosterone levels. Extracellular levels of 5-HT and its metabolite 5-hydroxy-indole acetic acid (5-HIAA) were measured using in vivo microdialysis. The rats received an intravenous (i.v.) infusion of the steroid synthesis-inhibitor metyrapone (150 mg/kg/ml) in order to manipulate circulating corticosterone levels. Three hours later, the monoamine oxidase inhibitor pargyline (15 mg/kg/2 ml i.v.) was administered to produce an accumulation of extracellular 5-HT. Pargyline administration led to a four fold increase in 5-HT levels, while reducing 5-HIAA by 45%. Metyrapone pretreatment blocked the pargyline-induced rise in plasma corticosterone to baseline levels and diminished the pargyline-induced increase in 5-HT, without affecting 5-HIAA levels. Thus, the data suggest that a decrease in availability of corticosterone for its receptors by metyrapone diminished the 5-HT synthesis rate. Since plasma corticosterone levels during this blockade are still low, it is assumed that brain glucocorticoid receptor occupation is reduced, while mineralocorticoid receptors are still substantially occupied. Therefore the present results support the hypothesis that corticosterone through glucocorticoid receptor activation enhances 5-HT synthesis rate and release in the dorsal hippocampus.

Enhanced 5-HT1A receptor expression in forebrain regions of aggressive house mice

The brain 5-HT1A receptor system in male wild house mice selected for high and low offensive aggression was investigated by autoradiographic analysis of in situ hybridization and radioligand binding. In high-aggressive mice, characterized by a short attack latency, the rise in plasma corticosterone concentration during the early dark phase was reduced. At that time the level of 5-HT1A mRNA in the dorsal hippocampus (dentate gyrus and CA1) was twice the amount measured in low-aggressive mice that had long attack latency and high plasma corticosterone level. Increased postsynaptic 5-HT1A receptor radioligand binding was found in dentate gyrus, CA1, lateral septum, and frontal cortex. No difference in ligand binding was found for the 5-HT1A autoreceptor on cell bodies in the dorsal raphe nucleus. In conclusion, genetic selection for high offensive aggression co-selects for reduced (circadian peak) level in plasma corticosterone and increased postsynaptic 5-HT1A receptor number in limbic and cortical regions.

Adrenaline release by the 5-HT1A receptor agonist 8-OH-DPAT is partly responsible for pituitary activation

In male Wistar rats the effect of adrenalectomy on pituitary activation by the 5-HT1A receptor agonist, 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT), was studied. Rats were injected intravenously with 8-OH-DPAT (0.10 mg/kg) in their home cages. Blood samples were withdrawn from freely moving cannulated rats for determination of plasma adrenaline and plasma adrenocorticotropin hormone (ACTH). Adrenalectomized rats showed almost no measurable amounts of plasma adrenaline, but these animals had elevated baseline plasma (ACTH levels as compared to sham-operated rats. 8-OH-DPAT treatment led to a large plasma adrenaline response in the sham-operated animals, which was abolished after adrenalectomy. The plasma ACTH response to 8-OH-DPAT was significantly diminished in the adrenalectomized rats as compared to sham animals. This blunted ACTH response in adrenalectomized rats, however, was still considerable in magnitude. The present data thus indicate that the plasma ACTH response to 8-OH-DPAT is due to at least two different mechanisms. First, via 5-HT1A receptor-mediated adrenaline release, which may consequently stimulate the pituitary. Second, a direct action of 8-OH-DPAT on hypothalamic 5HT1A receptors is assumed, independent of peripheral adrenaline release.

Mineralocorticoid and glucocorticoid receptor antagonists in animal models of anxiety

The behavioral effects of intracerebroventricular (i.c.v.) administration of a specific mineralocorticoid receptor (MR) antagonist [RU28318 (10-50 ng/2 microliters)], a glucocorticoid receptor (GR) antagonist [RU38486 (1-50 ng/2 microliters)], or both antagonists (50 ng/2 microliters), were studied in two different animal models of fear and anxiety in rats. In the defensive burying paradigm simultaneous blockade of MR and GR increased immobility behavior, whereas a small decrease in defensive burying was seen. In the fear-potentiated startle test concurrent MR and GR blockade led to an increase in fear-potentiated startle at the highest loudness level (105 dB). In both tests the antagonists were not effective when given separately. The findings are discussed in terms of the involvement of GR and MR in neural mechanisms of fear and anxiety.

Behavioral stress response of genetically selected aggressive and nonaggressive wild house mice in the shock-probe/defensive burying test

Genetically selected aggressive and nonaggressive male wild house mice were tested in the shock-probe/defensive burying test: Five distinct behaviors (burying, immobility, rearing, grooming, and exploration) were recorded in two environmental situations: fresh and home cage sawdust. Nonaggressive animals, characterized by a Long Attack Latency (LAL), showed more immobility in both test situations than animals having Short Attack Latencies (SAL), whereas SAL males displayed more defensive burying than LAL ones when tested with fresh sawdust. Testing with home cage sawdust, however, resulted in the same duration of defensive burying in SAL and LAL. These results support earlier findings about the existence of two heritable, fundamentally different strategies to cope with aversive situations. Aggressive (SAL) animal react actively to environmental challenges, whereas nonaggressive animals react actively or passively, depending on the characteristics of the stressful environment. These mouse lines, selected for attack latency, i.e., aggression, may, therefore, be important tools to unravel the genetic architecture underlying the physiological and neuronal mechanisms of behavioral strategies towards stressful events.

Antisense to the glucocorticoid receptor in hippocampal dentate gyrus reduces immobility in forced swim test

Immobility time of rats in the forced swim test was reduced after bilateral infusion of an 18-mer antisense phosphorothioate oligodeoxynucleotide targeted to the glucocorticoid receptor mRNA into the dentate gyrus of the hippocampus. Vehicle-, sense- and scrambled sequence-treated animals spent significantly more time immobile than antisense-treated animals during the initial test. Immunolabeling of the glucocorticoid receptor in brain sections demonstrated a reduced expression of glucocorticoid receptor proteins in antisense-treated dentate gyrus compared to the contralateral sense-treated dentate gyrus or contralateral scrambled sequence-treated dentate gyrus. During the initial test the time spent on immobility was also reduced when rats were treated with the glucocorticoid receptor antagonist RU38486 (17 beta-hydroxy-11 beta-(4-dimethylamino-phenyl)17 alpha-(1-propnyl)estra-4,9-diene-3-one)) 6 h (but not 1 h) earlier. These results demonstrate the participation of glucocorticoid receptors in the expression of immobility in a forced swim test during the initial test.

Potential anxiolytic properties of R-(+)-8-OSO2CF3-PAT, a 5-HT 1A receptor agonist

The anxiolytic property of R-(+)-8-OSO2CF3-PAT(R-(+)-8- [[(trifluoromethyl)sulfonyl]oxy]-2-(n-propyl-amino)tetralin), a 5-HT1A receptor agonist, was evaluated in Wistar rats by means of animal models of anxiety, the conditioned defensive burying model and the conditioned stress-induced freezing response followed by the elevated plus-maze test, respectively. In addition, the 5-HIAA/5-HT ratio (5-hydroxy-indole acetic acid/5-hydroxytryptamine) of rat brain homogenates was studied. Acute drug administration resulted in abolition of the burying behaviour (3 mg/kg i.p.), a dose-dependent decrease of rearing and induction of hyperphagia. R-(+)-8-OSO2CF3-PAT had no effect on conditioned footshock-induced freezing behaviour but increased open-arm activity in the rats on the plus-maze. The 5-HIAA/5-HT ratio was decreased in the lateral septum (1 and 3 mg/kg), dorsal hippocampus (3 mg/kg) and somatosensory cortex (3 mg/kg), implying that R-(+)-8-OSO2CF3-PAT affects particularly the limbic system in anxiety-inducing situations.

Forebrain pathways and their behavioural interactions with neuroendocrine and cardiovascular function in the rat

1. The forebrain is a major organizer of the complex behavioural, physiological and neuroendocrine responses to environmental challenges of a stressful nature. 2. Combined physiological and neuroanatomical studies suggest that a specific forebrain-brain stem network, composed of connections between the central nucleus of the amygdala, the paraventricular nucleus of the hypothalamus, the mesencephalic cuneiform nucleus, the parabrachial nucleus and the dorsal motor nucleus of the vagus nerve, may be important for integrating behavioural and physiological responses. 3. Based on studies using bilateral electrolytic lesions of the central nucleus of the amygdala, it has become clear that the central nucleus of the amygdala is one of the key structures involved in unconditioned responses to inescapable footshock. These responses include freezing behaviour, tachycardia and the release of adrenaline, noradrenaline, prolactin and corticosterone. However, this nucleus is involved only in the freezing behaviour and bradycardiac responses to conditioned emotional stress or to social defeat. 4. Both peptidergic (corticotropin releasing hormone and vasopressin/oxytocin) and aminergic (noradrenaline and dopamine) mechanisms in the central amygdala are involved in the regulation of integrated behavioural, physiological and neuroendocrine stress responses. This is indicated by studies with an infusion of an agonist and/or antagonist of the peptides or neurotransmitters into the central amygdala of freely moving rats. Sympathetic cardiac control is intensified by corticotropin releasing hormone and oxytocin, probably by inhibiting vagal output. In contrast, vagal activity is facilitated by vasopressin, noradrenaline and dopamine.

Socially defeated male rats display a blunted adrenocortical response to a low dose of 8-OH-DPAT

The study examined in male Wistar rats the influence of social defeat on the neuroendocrine stress response system using injection of the 5-HT1A receptor agonist, 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT), as the pharmacological challenge. Social defeat was defined by the submissive postures displayed by the Wistar rats which were threatened and attacked by Tryon Maze Dull S3 rats for 10 min. 18-20 h after social defeat, the defeated rats were injected intravenously (i.v.) with a low and high dose of 8-OH-DPAT in their home cages. Blood samples were withdrawn from the freely moving cannulated rats for determination of plasma corticosterone and catecholamines. The corticosterone response to the low dose of 8-OH-DPAT (0.05 mg/kg, i.v.) was significantly diminished in the defeated rats as compared to the controls, but this dose failed to affect catecholamine concentrations. The high dose of 8-OH-DPAT (0.15 mg/kg, i.v.) significantly elevated corticosterone and adrenaline levels in defeated and control rats to the same extent, whereas no effect on noradrenaline was found. The present data thus indicate that social defeat blunts 5-HT1A receptor-mediated adrenocortical activation probably via a decrease in the sensitivity of a population of postsynaptic 5-HT receptors.

Anxiolytic-like effects of selective mineralocorticoid and glucocorticoid antagonists on fear-enhanced behavior in the elevated plus-maze

The effects of intracerebroventricular (ICV) administration of the mineralocorticoid receptor (MR) antagonist, RU28318, and the glucocorticoid receptor (GR) antagonist, RU38486, were studied on behavior of rats exposed to a compartment previously associated with a stressor, and placed subsequently in an elevated plus-maze test. Fear-motivated immobility behavior was attenuated by the MR antagonist in a dose of 50 or 100 ng ICV, whereas the GR antagonist alone or simultaneous administration of both antagonists had no significant effect. In the elevated plus-maze, immediately after the exposure to the conditioned stressor, both the GR antagonist (50 ng) and MR antagonist (50 ng) increased the percentage of time the rats spent on open arms, and increased the amount of entries into these open arms. These data are interpretated in terms of the involvement of the GR and MR in fear and anxiety.

Effect of corticotropin-releasing factor antagonist on behavioral and neuroendocrine responses during exposure to defensive burying paradigm in rats

Defensive burying behavior is a coping strategy in rodents in response to an aversive stimulus where fear will facilitate burying and treatment with anxiolytics will result in less burying. To test the hypothesis that endogenous corticotropin-releasing factor (CRF) is involved in the defensive burying response, the effects of an ICV CRF antagonist were tested on defensive burying behaviors as well as the plasma adrenocorticotropic hormone (ACTH) and plasma corticosterone response. Rats were allowed to self-administer one mild electric shock (1.0 mA) through a probe mounted on the wall of the home cage by briefly touching it. Following this shock, control rats typically display burying behavior, as defined as moving the bedding material toward and/or over the shock probe. A CRF antagonist, alpha-hel CRF9-41, was administered ICV (1, 5, and 25 micrograms) 1 min after they received the shock. The 5 micrograms dose of the CRF antagonist significantly attenuated the time spent in defensive burying compared to vehicle-treated controls. The 5 and 25 micrograms doses of alpha-hel CRF9-41 increased the latency to display defensive burying. However, the enhanced release of plasma ACTH and plasma corticosterone concentrations in the stressed animals was not significantly modified over the 15-min period by either of the three doses of CRF antagonist. The results suggest that endogenous CRF is involved in the expression of defensive burying behavior and that the brain CRF receptors modulating the behavioral response may be different from the CRF receptors modulating the hormonal response of defensive burying.

Life-spanning behavioural and adrenal dysfunction induced by prenatal hypoxia in the rat is prevented by the calcium antagonist nimodipine

The long-term behavioural effects of prenatal chronic anaemic hypoxia were investigated in young (5 months old), late adult (19 months) and aged Wistar rats (23-26 months). Sodium nitrite (2 g/l) offered in the drinking water during the second half of pregnancy served to evoke prenatal hypoxia. In parallel to nitrite treatment the Ca2+ channel blocker nimodipine (10 mg/kg) or vehicle alone was administered intragastrically once daily. Open-field activity, intermale social behaviour, learning ability in a black-white discrimination paradigm and fear-induced emotionality were assessed at different ages. Plasma corticosterone response to novelty stress was measured by blood sampling through chronic venous canulas at the age of 28 months. The nitrite-exposed 5-month-old offspring started exploration in a novel open-field with considerable delay. This delayed start-latency was augmented in 19- and 23-month-old rats, pointing to exaggerated suppression of behavioural arousal. Nitrite-induced hypoxia decreased the duration of social interactions during ageing. Aged rats exposed to nitrite were unable to learn a black-white discrimination but showed a normal generalized conditioned fear response (immobility) to the test situation as a whole. The conditioned fear-induced vocalization was more frequent among hypoxic aged animals. The aged hypoxic rats displayed a prolonged plasma corticosterone stress response and had higher adrenal weight than their controls. The abnormal open-field, social, learning and emotional behaviours, as well as the altered plasma corticosterone response, were prevented by prenatal nimodipine treatment.

Central actions of corticotropin-releasing hormone (CRH) on behavioral, neuroendocrine, and cardiovascular regulation: brain corticoid receptor involvement

The effect of intracerebroventricular (icv) infused corticotropin-releasing hormone (CRH), 300 ng, infused at a rate of 16.67 ng/min during 18 min and its relation to the functioning of brain corticoid receptors was investigated in freely moving rats in their home cages. Behavior was sampled before, during, and after the CRH infusion. Cardiovascular measurements were made via a chronically implanted catheter in the descending aorta. Blood samples were withdrawn to determine adrenal hormone concentration. Central administration of the brain mineralocorticoid-like receptor (MR) antagonist (RU 28318, 100 ng) and the glucocorticoid receptor (GR) antagonist (RU 38486, 100 ng) 60 min before CRH infusion served to manipulate adrenal steroid states in the brain. CRH infusion caused behavioral activation which was associated with an increase in heart rate (HR) and mean arterial blood pressure (MAP). Increased plasma corticosterone and norepinephrine levels were observed, while a minor elevation of epinephrine (E) levels also occurred. Both corticoid receptor antagonists failed to affect the CRH-induced behavioral activation. Administration of the GR antagonist significantly enhanced the magnitude of the CRH-induced increase in E, whereas the effect of the MR antagonist just failed to reach significance. These findings suggest the involvement of central corticoid receptors in sympathoadrenomedullary feedback mechanisms. The MR antagonist elevated baseline MAP probably thereby suppressing the magnitude of the CRH response. The increase in HR was diminished by both antagonists shortly after CRH infusion. Together, the data suggest involvement of brain corticosteroid receptor-mediated processes in neuroendocrine and cardiovascular effects of CRH.

Mesencephalic cuneiform nucleus and its ascending and descending projections serve stress-related cardiovascular responses in the rat

The aim of the present study was to explore the neuroanatomic network that underlies the cardiovascular responses of reticular formation origin in the region of the cuneiform nucleus (CNF). The study was performed in urethane anesthetized male Wistar rats. The left iliac artery was supplied with a catheter for the measurement of systemic blood pressure. Low intensity electrical stimulation of the mesencephalic reticular formation (MRF) in the vicinity of the CNF always resulted in pressor and bradycardiac responses, whereas stimulation in the parabrachial nucleus (PB) and Kölliker-Fuse nucleus (KF) led to a pressor response and a small tachycardiac response. The cuneiform area may be placed in the center of a circuit that serves a specific autonomic response pattern to stress: parallel activation of the sympathetic (pressor response) and parasympathetic limb (bradycardia). The efferent connections of the effective stimulation sites in the MRF and the CNF area, were investigated by anterograde tracing with the lectin Phaseolus vulgaris leucoagglutine (PHA-L). The CNF sends descending fibers to the gigantocellular reticular nuclei (GI), the motor nucleus of the vagus (DMNV) and nucleus tractus solitarius (NTS). These projections are probably involved in the bradycardiac response to stimulation. The descending pathway to the NTS/DMNV and GI may therefore be the parasympathetic limb of the circuit. Furthermore, the CNF sends ascending fibers to limbic forebrain areas and descending fibers to the PB-KF complex. The KF in its turn projects to the rostroventrolateral medullary nucleus (RVLM) and the intermediolateral cell column (IML). These latter projections are partly involved in producing the pressor response and thereby represent the sympathetic limb of the circuit. Accordingly, the transection of the descending fibers from the CNF to the PB-KF complex resulted in a decreased pressor and an increased bradycardiac response. This suggests that a baroreceptor reflex-induced bradycardia which results from blood pressure increase can be excluded as the origin of the stimulation-induced bradycardia, and that the pressor and bradycardiac responses are two independent moieties. It cannot be excluded that ascending fibers from the CNF are also involved in producing the pressor response. On the basis of the present physiological and neuroanatomical study, a brain circuit has been proposed in which the cuneiform nucleus has a central position. The described brain circuit may serve a passive coping strategy to novel, painful or threatening stimuli during which the animals show orientation/attention or freezing behavior accompanied by a bradycardiac and pressor response.

Neuroendocrine and behavioral responses during conditioned active and passive behavior in the defensive burying/probe avoidance paradigm: effects of ipsapirone

Plasma epinephrine (E), norepinephrine (NE), and corticosterone (CORT) concentrations were determined in the rat before, during, and after a 15-min exposure to a nonelectrified probe on day after receiving electric shock (1.5 mA) through a probe mounted on the wall of the home cage. Rats displayed burying (active coping) if sawdust was provided on the floor and immobility (passive coping) if bedding was absent both during training and testing. The conditioned burying was accompanied by high plasma NE but low E and CORT concentrations, whereas immobility was associated with high CORT and low NE levels. A forced switch from the active to passive coping (training with and testing without sawdust) led to the highest rise in E concentration. The 5-HT1A agonist ipsapirone, with anxiolytic properties, dose-dependently (0.5 and 2.5 mg/kg, IV) reduced defensive burying behavior and increased the amount of time spent on feeding behavior in the presence of bedding material. Both plasma E and CORT levels were further elevated by the higher dose of ipsapirone. In the absence of bedding material, ipsapirone failed to affect immobility behavior, but it dose-dependently elevated the stress-induced increase in E, NE, and CORT concentrations. Accordingly, the behavioral anxiolytic action of the 5-HT1A agonist ipsapirone was restricted to active coping, whereas neuroendocrine activation by the drug was present in all conditions. It is suggested that the effects of ipsapirone on behavioral coping and neuroendocrine regulation are produced by different populations of 5-HT1A receptors in the brain.

Behavioral and cardiac responses after intracerebroventricular corticotropin-releasing hormone (CRH) administration: role of adrenal cortical hormones

Intracerebroventricularly (icv) administered corticotropin-releasing hormone (CRH) produces a dose-dependent increase in heart rate in association with behavioral activation. The present study was designed to investigate whether these CRH-induced responses are dependent on adrenal function. The effects of adrenalectomy (ADX) and subsequent corticosterone replacement were studied. Administration icv of 300 ng of CRH failed to produce behavioral activation and tachycardia in ADX rats. Corticosterone replacement restored the CRH-induced behavioral response to preoperative levels, whereas the CRH-induced tachycardia was partially restored. This latter result may be related to the fact that the baseline heart rate of ADX animals appeared to be significantly higher than that of corticosterone-treated ADX animals. It is concluded that circulating adrenal corticosterone in ADX rats is involved in the expression of the behavioral and cardiac effect of central CRH.

Adrenal hormones in rats before and after stress-experience: Effects of ipsapirone

The present study was designed to investigate the effects of the anxiolytic 5-HT1A receptor agonist ipsapirone on the hormonal responses in rats under nonstress and stress conditions by means of repeated blood sampling through an intracardiac catheter. Ipsapirone was given in doses of 2.5, 5, 10, and 20 mg/kg (IP) under nonstress conditions in the home cages of the rats. Plasma corticosterone levels increased in a dose-dependent way in the dose range of 5 to 20 mg/kg, whereas the plasma catecholamines were only significantly increased with the highest dose of the drug. The effect of ipsapirone in control and in stressed rats was studied with the selected dose of 5 mg/kg. Conditioned fear of inescapable electric footshock (0.6 mA, AC for 3 s) given one day earlier was used as stressor. Surprisingly, ipsapirone potentiated the magnitude of the neuroendocrine responses. Rats receiving an inescapable footshock 1 day earlier showed a further elevated corticosterone response to the 5-HT1A receptor agonist ipsapirone even before exposing them to the conditioned stress situation. The present findings suggest that if an animal has no possibilities to escape or avoid a noxious event, functional hypersensitivity will develop in the serotonergic neuronal system, which is reflected in the increased responsiveness of the HPA axis to a 5-HT1A agonist challenge.

Conditioned neuroendocrine and cardiovascular stress responsiveness accompanying behavioral passivity and activity in aged and in young rats

Mean arterial pressure (MAP), heart rate (HR), plasma epinephrine (E), plasma norepinephrine (NE), and plasma corticosterone (CORT) were measured in 3-month- and 24-month-old male Wistar rats exposed to a conditioned emotional stress response (CER) paradigm and a conditioned defensive burying (CDB) paradigm. In the CER situation blood samples were taken during reexposure to the training environment one day after a single inescapable footshock (0.6 mA, AC for 3 s) had been administered. In the CER paradigm the young rats displayed passive behavior (immobility) accompanied by an increase in plasma levels of CORT and E, whereas both the control and conditioned animals showed increased NE responses. Previously shocked aged rats exhibited an attenuated plasma NE response, whereas levels of E remained elevated to a greater extent. Aged animals showed elevated basal levels of CORT one day after footshock administration. Stress-induced immobility was preserved in the aged rats. These animals had an increase in basal MAP values and a decrease in basal HR values compared to young ones. In the CDB paradigm, rats were exposed to a nonelectrified probe 1 day after the repeated shock (2 mA/contact) procedure. Young rats displayed defensive burying accompanied by increments in MAP, HR, CORT, and NE. The aged animals showed similar hormonal, autonomic, and behavioral stress responses. Thus, the age-related alterations in neuroendocrine and autonomic response patterns are apparent in stressed animals during behavioral passivity in absence of control (CER) rather than during active control (defensive burying).

Involvement of hypothalamic serotonin in activation of the sympathoadrenomedullary system and hypothalamo-pituitary-adrenocortical axis in male Wistar rats

Infusion of the 5-HT1A receptor agonist, 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) (2.5-20 micrograms in 1 microliter during 15 min), into the paraventricular nucleus of the hypothalamus (PVN) in the rat dose dependently increased plasma adrenaline and corticosterone concentrations, without affecting plasma noradrenaline concentrations. The highest dose also increased plasma glucose levels significantly. The results suggest that both the sympathoadrenomedullary system and the hypothalamo-pituitary-adrenocortical axis are activated after stimulation of 5-HT1A receptors in the PVN.

Behavioral and neuroendocrine response to psychosocial stress in male rats: the effects of the 5-HT 1A agonist ipsapirone

The effect of the 5-HT 1A agonist ipsapirone on the behavior, plasma catecholamine, and corticosterone levels was studied in male Wistar rats during the psychosocial stress of confrontation with a confined dominant opponent 24 hr after defeat. The effect of the drug was also studied during a predefeat confrontation with the confined (would-be dominant) rat. Blood samples were withdrawn via a permanent heart catheter. The drug (5 mg/kg, ip) or vehicle was given 30 min before transportation to the experimental room. Ipsapirone had no major effects on the plasma hormone concentrations and had no influence upon the behavioral response to the confined rat. At the postdefeat test ipsapirone led to a significant increase of immobility, whereas both rearing and time spent sniffing the cage were diminished. Postdefeat psychosocial stress resulted in an increase of the hormone, particularly catecholamine levels. These responses were further elevated by the drug. The presence of high corticosterone levels in the home cage after postdefeat ipsapirone treatment leads to the hypothesis that postsynaptic 5-HT 1A receptor hypersensitivity develops after the social stress of defeat.

Behavioural physiology of serotonergic and steroid-like anxiolytics as antistress drugs

Pharmacological studies are useful tools to understand the neurobiological basis of behavioural and physiological stress mechanisms. Ipsapirone, a 5-HT1A autoreceptor agonist is a representative of novel anxiolytics without the disadvantages of benzodiazepam-like drugs. Behavioural, physiological and neuroendocrine studies in the rat are reviewed which were aimed to investigate the antistress properties of ipsapirone during reexposure to various conditioned emotional stress situations. It is demonstrated that in certain situations, probably due to a stress-induced sensitisation of postsynaptic 5-HT1A receptors, anxiolytic doses of the drug may show prostress (anxiogenic) behavioural and neuroendocrine effects. Furthermore, brain corticosteroid receptors, probably interacting with the serotonergic transmission, are involved in anxiogenic/prostress processes. In this respect antagonists of the brain mineralocorticoid-like (type I) receptors may be important antistress drugs of the future.