Differential effects of periodic maternal separation on adult stress coping in a rat model of extremes in trait anxiety

We studied interactions of genetic and environmental factors shaping adult emotionality and stress coping, and tested the hypothesis that repeated periodic maternal deprivation (PMD) exerts differential effects on adult behavioral and neuroendocrine stress responsiveness in dependence on the genetic predisposition to either hyper- or hypo-anxiety. Exposure of male Wistar rats bidirectionally bred for either high (HAB) or low (LAB) anxiety-related behavior to PMD between postnatal days 2 and 15 resulted in a behavioral approximation of the selected lines. This was reflected by test-dependent signs of reduced anxiety-related behavior in adult HAB rats and of enhanced levels of anxiety in LAB rats compared with their corresponding unstressed controls. In addition to behavioral parameters, differential effects of PMD were also seen with respect to the responsiveness of the hypothalamo-pituitary-adrenocortical axis to acute stressor exposure (novel environment) in adulthood. The corticotrophin (ACTH) and corticosterone hyper-responses seen in control rats of the HAB line compared with those of the LAB line became attenuated in PMD-HAB rats, whereas PMD did not significantly alter neuroendocrine responses in LAB rats. Thus, as a result of PMD, both ACTH and corticosterone responses became indistinguishable between HAB and LAB rats. Although HAB dams spent more time on the nest with the litter compared with LAB dams during the first 5 days postpartum, licking and grooming behavior did not differ between the lines prior to separation, and was found to be increased to the same extent in both HAB and LAB dams during the first hour immediately after reunion with the pups. In contrast to early life stress, exposure of adult HAB and LAB rats to a 10-day unpredictable stress schedule failed to alter their emotional measures. The mitigating effect of PMD on both behavioral and neuroendocrine parameters in rats representing extremes in trait anxiety might reflect an evolutionary benefit as the genetic variability among individuals of a species is sustained while allowing adequate responses to potentially dangerous stimuli in adulthood dependent on early life conditions.

Neuropeptides in anxiety modulation

This review is focused on the involvement of neuropeptides in the modulation of physiological and pathological anxiety. Neuropeptides play a major role as endogenous modulators of complex behaviours, including anxiety-related behaviour and psychopathology, particularly due to their high number and diversity, the dynamics of release patterns in distinct brain areas and the multiple and variable modes of interneuronal communication they are involved in. Manipulations of central neuropeptidergic systems to reveal their role in anxiety (and often comorbid depression-like behaviour) include a broad spectrum of loss-of-function and gain-of-function approaches. This article concentrates on those neuropeptides for which an involvement as endogenous anxiolytic or anxiogenic modulators is well established by such complementary approaches. Particular attention is paid to corticotropin-releasing hormone (CRH) and vasopressin (AVP) which, closely linked to stress, neuroendocrine regulation, social behaviour and learning/memory, play critical roles in the regulation of anxiety-related behaviour of rodents. Provided that their neurobiology, neuroendocrinology and molecular-genetic background are well characterized, these and other neuropeptidergic systems may be promising targets for future anxiolytic strategies.

Arginine vasopressin and adrenocorticotropin secretion in response to psychosocial stress is attenuated by ethanol in sons of alcohol-dependent fathers

Familial risk and environmental stress promote the development of alcohol dependence. We investigated whether a positive family history of alcoholism affects the neuroendocrine response to a standardized laboratory stress test in healthy subjects without alcohol use disorders. Twenty-four high-risk subjects with a paternal history of alcoholism (PHA) and 16 family history negative (FHN) controls were evaluated. Psychosocial stress was induced by having subjects deliver a 5-min speech and mental arithmetics in front of an audience on separate days, after drinking either placebo or ethanol (0.6 g/kg) in a randomized sequence. Adrenocorticotropin (ACTH) was measured in 10 plasma samples covering up to 75 min after the stress test. Plasma arginine vasopressin (AVP) was determined before the stressor, at the time of maximum ACTH secretion, and at 75 min after stress onset. The stress test induced a phasic increase in ACTH secretion. At the time of maximum ACTH, AVP was significantly increased in relation to baseline. Compared to placebo, alcohol administration significantly attenuated maximum ACTH concentration in PHA but not FHN subjects, and decreased AVP measured in the same samples in PHA but not FHN subjects. We conclude that activation of the hypothalamic-pituitary-adrenal system by psychosocial stress is accompanied by an increase in peripheral plasma AVP levels. Secretion of both ACTH and AVP suggest that alcohol attenuates the stress response selectively in PHA but not FHN subjects. This might imply some short-term positive alcohol effect in sons of alcoholics, but also constitute a mechanism by which their risk to develop alcohol use disorders is increased.

Two Wistar Rat Lines Selectively Bred for Anxiety-Related Behavior Show Opposite Reactions in Elevated Plus Maze and Fear-Sensitized Acoustic Startle Tests

Two Wistar rat lines selectively bred for high (HAB), and low anxiety-related behavior (LAB) on the elevated plus maze were tested for the fear-sensitized acoustic startle response. The study of male rats from the F9 generation revealed a higher anxiety level of HAB rats on the elevated plus maze. However, the LAB rats displayed a higher baseline and fear-sensitized acoustic startle response compared to HAB rats, although the two rat lines did not differ in freezing duration during the interstimulus intervals in the startle experiment (neither before, nor after, footshocks). Counts of neurons immunoreactive for corticotropin-releasing factor and neuropeptide Y in amygdaloid nuclei did not reveal any differences between the two lines, which is in marked contrast to findings in the Roman rat lines. The data indicate that opposite types of anxiety/fear responses are elicited in HAB/LAB rats in the elevated plus maze and fear-sensitized startle tests. Moreover, the animals displayed a differential fear response in the startle experiment, as assessed by measuring the fear-sensitized startle response and freezing.

Hypothalamic neuropeptide release after experimental subarachnoid hemorrhage: in vivo microdialysis study

OBJECTIVES

As evidence exists about independent regulation of peripheral and central release of the vasoactive and natriuretic neuropeptides arginine-vasopressin (AVP) and oxytocin (OXT), we investigated their release patterns following subarachnoid hemorrhage (SAH).

MATERIALS AND METHODS

After injection of 0.1 ml arterial blood or saline into the great cistern of 33 Wistar rats, AVP and OXT levels were measured in blood and by microdialysis in the hypothalamic supraoptic (SON) and paraventricular nucleus (PVN). For statistical analysis, the analysis of variance (ANOVA) was used with Tukey HSD post hoc ANOVA tests to determine specific group differences.

RESULTS

Plasma AVP and OXT peaked 2 h after SAH (P < 0.05), and normalized at 4 h. In the SON, both AVP and OXT peaked 4 h after SAH (P < 0.05). In the PVN, AVP increased in both groups (P < 0.05), while no OXT release occurred. By the sham group, any effect of experimental procedure was excluded.

CONCLUSIONS

The SAH-specific central neuropeptide release, which exceeded peripheral release and continued longer, may contribute to pathophysiological events following SAH.

Effectiveness of a Disease Management Programme for Patients with Type 2 Diabetes Mellitus and Albuminuria in Primary Care - the PROSIT® Project (Proteinuria Screening and Intervention)

Aims. To evaluate the structured PROSIT(R) disease management programme for high-risk diabetic patients in primary care with respect to the cardio-vascular risk profile and mortality. Subjects and Methods. Retrospectively 55 albuminuric Type 2 diabetic patients included into the PROSIT(R) programme from 1994 to 1999 (intervention group: age 66.6 +/- 10.5 years, known duration of diabetes 8.9 +/- 6.5 years) were compared with 58 albuminuric patients not participating in the PROSIT(R) programme (control group: age 68.5 +/- 10.4 years, known duration of diabetes 8.5 +/- 6.7 years). Within PROSIT(R) a structured multifactorial intervention programme was applied. The main characteristics of this intervention were strict follow-ups of the patient's risk profile every three months and the use of quality management methods (definition of target values, structured documentation, central data feedback with diagnostic and therapeutic recommendations based on European guidelines). The cardio-vascular risk profile, therapeutic intervention, and secondary diabetic complications were compared between both groups in 1994 and 1999. Results. In the period from 1994 to 1999 the intervention group showed a significant improvement in the vascular risk profile, while the control group did not. In 1999 the mean arterial blood pressure was significantly lower compared to the control group (115 +/- 13 mm Hg vs. 125 +/- 16 mm Hg, p < 0.05). The HbA1c improved only in the intervention group and in 1999 it was significantly lower than in the control group (7.0 +/- 1.3 % vs. 8.4 +/- 1.8 %, p < 0.01). Moreover, the occurrence of clinical endpoints in the intervention group could be reduced: Both the mortalitly rate (14.5 % vs. 34.5 %, p < 0.05) and the rate of new myocardial infarctions (6 % vs. 20 %, p < 0.05) of the intervention group were significantly lower. Conclusions. Participation of albuminuric Type 2 diabetic patients and their physicians in a structured intervention programme showed positive effects on the cardio-vascular risk profile and endpoints compared with a group of non-participating patients and physicians.

Improved ultrasound examination of pancreas grafts in type 1 (insulin-dependent) diabetic patients using tissue harmonic imaging

BACKGROUND

Combined kidney/pancreas transplantation is an established therapy for type 1 diabetic patients with end-stage renal disease. Ultrasound examinations are valuable noninvasive methods for postoperative monitoring of transplant recipients. Kidney grafts are easily to detect, whereas pancreas grafts are surrounded or covered by small bowel loops, which makes the examination much more difficult.

PATIENTS AND METHODS

Thirty-three simultaneous pancreas and kidney recipients (SPK) were examined by conventional sonography at 3.4 MHz and THI sonography (pulse inversion, 2.3 MHz) by an investigator experienced in abdominal ultrasound. The images were graded by two "blinded readers" using a scale (1-best image quality, 2-second best, 3-worst) with regard to tissue penetration and detail characterization of the pancreas grafts. The graders were unaware of the sonographic technique, respectively. Statistical evaluation was performed by the Mann-Whitney U test.

RESULTS

In 25 cases (78%) pancreas grafts were detected by conventional sonography. The detection rate was higher using THI sonography, namely 29 cases (91%). Grading for tissue penetration revealed a mean value of 2.05 +/- 0.5 for conventional and 1.94 +/- 0.5 for THI sonography (P =.27). Detail characterization of the pancreas grafts was determined to show a mean value of 2.50 +/- 0.5 for conventional sonography and a significantly better mean value of 1.78 +/- 0.6 for THI sonography (P <.0001).

CONCLUSION

THI sonography improves the detection and the judgment of tissue characteristics of pancreas grafts. Penetration of ultrasound waves is not relevantly decreased by this new technique.

Nitric oxide is not involved in the control of vasopressin release during acute forced swimming in rats

Neurons of the hypothalamo-neurohypophyseal system (HNS) are known to contain high amounts of neuronal nitric oxide (NO) synthase (nNOS). NO produced by those neurons is commonly supposed to be involved as modulator in the release of the two nonapeptides vasopressin (AVP) and oxytocin into the blood stream. Previous studies showed that forced swimming fails to increase the release of AVP into the blood stream while its secretion into the hypothalamus is triggered. We investigated here whether hypothalamically acting NO contributes to the control of the AVP release into blood under forced swimming conditions. Intracerebral microdialysis and in situ hybridization were employed to analyze the activity of the nitrergic system within the supraoptic nucleus (SON), the hypothalamic origin of the HNS. A 10-min forced swimming session failed to significantly alter the local NO release as indicated both by nitrite and, the main by-product of NO synthesis, citrulline levels in microdialysis samples collected from the SON. Microdialysis administration of NO directly into the SON increased the concentration of AVP in plasma samples collected during simultaneous forced swimming. In an additional experiment the effect of the defined stressor exposure on the concentration of mRNA coding for nNOS within the SON was investigated by in situ hybridization. Forced swimming increased the expression of nNOS mRNA at two and four hours after onset of the stressor compared to untreated controls. Taken together, our results imply that NO within the SON does not contribute to the regulation of the secretory activity of HNS neurons during acute forced swimming. Increased nNOS mRNA in the SON after forced swimming and the increase in AVP release in the presence of exogenous NO under forced swimming points to a possible role of NO in the regulation of the HNS under repeated stressor exposure.

Born to be anxious: neuroendocrine and genetic correlates of trait anxiety in HAB rats

This review summarises behavioural, neuroendocrine, and genetic characteristics of Wistar rats bred for either high (HAB) or low (LAB) anxiety-related behaviour. Compared to LABs, HAB animals show signs of extreme trait anxiety in a variety of behavioural tests; they further prefer passive coping strategies, indicative of a genetically linked depression-like behaviour, and show signs of increased stress vulnerability. All behavioural parameters associated with trait anxiety are robust and consistent. Resembling psychiatric patients, HAB rats respond to exposure to ethologically relevant stressors with a hyper-reactivity of the hypothalamic-pituitary-adrenal axis and show a pathological outcome of the combined dexamethasone/corticotropin-releasing hormone (Dex/CRH) challenge test. Experimental evidence indicates that over-expression and -release of vasopressin in the hypothalamic paraventricular nucleus is responsible for these behavioural and neuroendocrine phenomena, making the neuropeptide gene a candidate gene of trait anxiety/depression. Indeed, preliminary molecular genetic approaches succeeded in identifying polymorphisms in the promoter structure of the vasopressin gene. This may have implications for understanding the molecular basis for individual variations in trait anxiety and for psychopathology.

Gastric emptying of solid and liquid meals in healthy controls compared with long-term type-1 diabetes mellitus under optimal glucose control

BACKGROUND

Neuropathy of the enteric nervous system and hyperglycaemia are regarded as the main causes of diabetic gastroparesis.

PATIENTS AND METHODS

In ten patients with Type-1 diabetes mellitus and sensomotoric neuropathy gastric emptying half times were compared with ten healthy controls by employing the 13C-octanoic acid and the 13C-sodiumacetate breath test, resp., following the intake of equally composed and isocaloric liquid and solid meals. Plasma glucose concentrations were controlled by permanent intravenous administration of insulin.

RESULTS

In diabetes mellitus gastric emptying half times after the intake of the liquid meal (p < 0.05) but not after ingestion of the solid meal were slightly prolonged. Gastric emptying half times in patients and controls were not different when liquid and solid meals were compared.

CONCLUSIONS

Acute hyperglycaemia appears to be more important than the neuropathy of the enteric nervous system in the pathophysiology of diabetic gastroparesis. The rate of gastric emptying is obviously not dependent on the phase of a meal, but rather on the composition and the caloric content.

[57-year-old patient with diplopia and headache]

A 57-year old patient presented with an 8 week history of headache and diplopia. Left-sided incomplete oculomotor nerve paresis was found, whereas further clinically relevant visual impairment was not seen. Magnetic resonance imaging of the head showed an extensive intra-, para- and suprasellar tumor which in combination with a markedly elevated serum prolactin level was identified as a macroprolactinoma. The symptoms began 7 years ago with a loss of libido and virility. The application of a dopamine agonist lead to a reduction of serum prolactin level to 0.5% of the initial value and a considerable tumor regression within three months. The development of oculomotor nerve paresis is an unusual manifestation of prolactinoma. By contrast, long-term medical history with slowly developing signs and symptoms of hypogonadotropic hypogonadism are often to be found in men. The delayed diagnosis is responsible for the high percentage of macroprolactinomas in male subjects.

[Neurobiology and genetics of anxiety in an animal model]

This paper presents a valid animal model of innate anxiety/depression: anxious (HAB) or non-anxious (LAB) rats, which show stable and robust responses in a variety of ethological tests. In addition to their extreme anxiety-related behavior, HAB animals are characterized by passive stress coping, an activated stress (HPA) axis, and increased stress vulnerability. The enhanced expression and release of arginine vasopressin (AVP) in the hypothalamus of HAB rats seem to underlie these phenomena. Accordingly, an AVP receptor antagonist attenuates anxiety-related behavior and normalizes the HPA axis and the dexamethasone/CRH test. Treatment with the antidepressive drug paroxetine reduces the overexpression of AVP and normalizes both the depression-like behavior and neuroendocrine correlates of anxiety/depression. The complex phenotyping led us to the conclusion that the AVP gene is likely to be a candidate gene of inborn anxiety. Partial genotyping of HAB animals results in the identification of polymorphisms (SNPs) in the promoter domain of the AVP gene, thus potentially leading to novel strategies of diagnosis and therapy of anxiety disorders and depression.

The high-affinity non-peptide CRH1 receptor antagonist R121919 attenuates stress-induced alterations in plasma oxytocin, prolactin, and testosterone secretion in rats

Evidence from basic and clinical research suggests that hyperactivity of central corticotropin-releasing hormone (CRH) circuits contributes to causality and course of affective disorders. Therefore, CRH receptor antagonists have attracted attention as potential therapeutics. We could previously show that the novel high-affinity non-peptide CRH 1 receptor antagonist R121919 significantly inhibits stress-induced corticotropin release and displays anxiolytic effects in rats selectively bred for high anxiety-related behavior. These animals are characterized by their innate hyper-reactivity of the hypothalamic-pituitary-adrenocortical system linked to an increased emotionality and therefore are suitable for the evaluation of CRH 1 receptor antagonists. Here we show that in addition to its effects on anxiety-related behavior and corticotropin secretion, R121919 attenuates the stress-induced release of corticosterone, prolactin, and oxytocin. Moreover, the decrease in plasma testosterone following exposure to stress is abolished by R121919. Our data indicate that antagonism of CRH 1 receptors may prevent stress-associated endocrine alterations.