Dimensions of emotionality in a rat model of innate anxiety

Emotionality is thought to be multidimensional, with "anxiety" representing one dimension. Dissecting emotional dimensions in animal models is an essential prerequisite for investigating the neurobiological mechanisms that underlie anxiety. The authors used factor analysis to investigate emotional dimensions in normal rats and rats bred for either high or low anxiety-related behavior. Hyperanxious rats were reduced in emotional dimensions in the elevated plus-maze by selection pressure, and a modified hole board test revealed a dissection of their emotionality with precisely defined dimensions. This enabled clear differentiation of "anxiety" from other emotional dimensions including risk assessment behavior and exploration. Factors extracted by analyzing data from a multiple-test battery corresponded to particular test characteristics rather than to emotional dimensions. The approach used might help to develop specific treatment strategies for anxiety disorders.

Social isolation after a single defeat reduces striatal dopamine transporter binding in rats

A single social defeat in male rats has long lasting physiological and behavioural consequences, which are similar to those seen in depressive patients. In addition, the housing conditions after social defeat appear to be crucial for the development of depression-like symptoms. Because the dopaminergic system is thought to be altered in depressive illness, we investigated the impact of individual and group housing on the temporal development of changes of dopamine transporter (DAT) binding in male rats after a single social defeat. The number of striatal DAT binding sites was reduced in animals that remained isolated after being defeated. The isolation length after social defeat amplified this effect, indicating a temporal development of the changes on the striatal DAT. In animals which returned to the familiar group after social defeat the density of striatal DAT binding sites was not affected. We conclude that social isolation after a single defeat reduces the number of DAT binding sites. In contrast, a familiar environment after a single social defeat appears to prevent the stress-induced alterations on the dopaminergic system. This finding suggests that housing conditions are critical when investigating the central nervous effects of social defeat in male rats.

The anxiolytic effect of the CRH(1) receptor antagonist R121919 depends on innate emotionality in rats

Hyperactivity of central corticotropin-releasing hormone (CRH) circuits appears to contribute to the symptomatology of affective and anxiety disorders and therefore CRH receptor antagonists have attracted attention as potential therapeutic agents. R121919, a novel high-affinity nonpeptide CRH(1) receptor antagonist, displaced (125)I-oCRH in rat pituitary, cortex and amygdala, but not in choroid plexus or cerebral blood vessels in vitro and in vivo, which is consistent with CRH(1) receptor antagonism. In vivo, R121919 significantly inhibited stress-induced corticotropin release in rats selectively bred for high- and low-anxiety-related behaviour but displayed anxiolytic effects in high-anxiety rats only. These data, corroborated by ex vivo receptor occupancy studies, suggest that this animal model is appropriate for the evaluation of CRH(1) receptor antagonists and that compounds such as R121919 will be beneficial whenever the central stress hormone system is hyperactive.

Meglitinide analogues in the treatment of type 2 diabetes mellitus

Type 2 diabetes mellitus is a complex heterogenous metabolic disorder in which peripheral insulin resistance and impaired insulin release are the main pathogenetic factors. The rapid response of the pancreatic beta-cells to glucose is already markedly disturbed in the early stages of type 2 diabetes mellitus. The consequence is often postprandial hyperglycaemia, which seems to be extremely important in the development of secondary complications, especially macrovascular disease. Therefore one of the main aims of treatment is to minimise blood glucose oscillations and attain near-normal glycosylated haemoglobin levels. Meglitinide analogues belong to a new family of insulin secretagogues which stimulate insulin release by inhibiting ATP-sensitive potassium channels of the beta-cell membrane via binding to a receptor distinct from that of sulphonylureas (SUR1/KIR 6.2). The pharmacokinetic and pharmacodynamic properties of repaglinide, the first drug of these new antihyperglycaemic agents on the market, and of nateglinide, which will be available soon, differ markedly from the currently used sulphonylureas [mainly glibenclamide (glyburide) and glimepiride]. Repaglinide and nateglinide are absorbed rapidly, stimulate insulin release within a few minutes, are rapidly metabolised in the liver and are mainly excreted in the bile. Therefore, following preprandial administration of these drugs, insulin is more readily available during and just after the meal. This leads to a significant reduction in postprandial hyperglycaemia without the danger of hypoglycaemia between meals. The short action of these compounds and biliary elimination makes repaglinide and nateglinide especially suitable for patients with type 2 diabetes mellitus who would like to have a more flexible lifestyle, need more flexibility because of unplanned eating behaviour (e.g. geriatric patients) or in whom one of the other first-line antidiabetic drugs, i.e. metformin, is strictly contraindicated (e.g. nephropathy with creatinine clearance < or = 50 ml/min). Meglitinide analogues act synergistically with metformin and thiazolidinediones (pioglitazone and rosiglitazone) and can be also combined with long-acting insulin (NPH insulin at bedtime). Therefore, these drugs enrich the palette of antidiabetic drugs and make the treatment more flexible and better tolerated, which both add to better metabolic control and support the empowerment and compliance of the patient. However, this will only be the case if the patient and the diabetes care team are trained for this new therapeutic schedule and the healthcare system is able to pay for these rather expensive drugs.

Selective activation of the hypothalamic vasopressinergic system in mice deficient for the corticotropin-releasing hormone receptor 1 is dependent on glucocorticoids

Deficiency of CRH receptor 1 (CRHR1) severely impairs the stress response of the hypothalamic-pituitary-adrenocortical (HPA) system and reduces anxiety-related behavior in mice. Intriguingly, in mice deficient for the CRHR1 (Crhr1-/-), basal plasma levels of ACTH are normal, suggesting the presence of compensatory mechanisms for pituitary ACTH secretion. We therefore studied the impact of the hypothalamic neuropeptides arginine vasopressin (AVP) and oxytocin (OXT) on HPA system regulation in homozygous and heterozygous Crhr1 mutants under basal and different stress conditions. Basal plasma AVP concentrations were significantly elevated in Crhr1-/- mice. AVP messenger RNA expression was increased in the paraventricular nucleus of Crhr1-/- mutants together with a marked increase in AVP-like immunoreactivity in the median eminence. Administration of an AVP V1-receptor antagonist significantly decreased basal plasma ACTH levels in mutant mice. After continuous treatment with corticosterone, plasma AVP levels in homozygous Crhr1-/- mice were indistinguishable from those in wild-type littermates, thus providing evidence that glucocorticoid deficiency is the major driving force behind compensatory activation of the vasopressinergic system in Crhr1-/- mice. Neither plasma OXT levels under several different conditions nor OXT messenger RNA expression in the paraventricular nucleus were different between the genotypes. Taken together, our data reveal a selective compensatory activation of the hypothalamic vasopressinergic, but not the oxytocinergic system, to maintain basal ACTH secretion and HPA system activity in Crhr1-/- mutants.

Acute transcranial magnetic stimulation of frontal brain regions selectively modulates the release of vasopressin, biogenic amines and amino acids in the rat brain

Using intracerebral microdialysis in urethane-anaesthetized adult male Wistar rats, we monitored the effects of acute repetitive transcranial magnetic stimulation (rTMS; 20 trains of 20 Hz, 2.5 s) on the intrahypothalamic release of arginine vasopressin (AVP) and selected amino acids (glutamate, glutamine, aspartate, serine, arginine, taurine, gamma-aminobutyric acid) and the intrahippocampal release of monoamines (dopamine, noradrenaline, serotonin) and their metabolites (homovanillic acid, 3,4-dihydroxyphenylacetic acid, 5-hydroxyindoleacetic acid). The stimulation parameters were adjusted according to the results of accurate computer reconstructions of the current density distributions induced by rTMS in the rat and human brains, ensuring similar stimulation patterns in both cases. There was a continuous reduction in AVP release of up to 50% within the hypothalamic paraventricular nucleus in response to rTMS. In contrast, the release of taurine, aspartate and serine was selectively stimulated within this nucleus by rTMS. Furthermore, in the dorsal hippocampus the extracellular concentration of dopamine was elevated in response to rTMS. Taken together, these data provide the first in vivo evidence that acute rTMS of frontal brain regions has a differentiated modulatory effect on selected neurotransmitter/neuromodulator systems in distinct brain areas.

[Increased clinical and economic advantages using PROSIT (proteinuria screening and intervention) in type 2 diabetic patients]

BACKGROUND AND OBJECTIVE

Even though there are simple and cost-effective means for the early diagnosis of diabetic nephropathy, only a small proportion of diabetics in Germany is regularly tests for microalbuminuria. On the basis of evidence-based knowledge and of international guidelines the PROSIT project (proteinuria screening and intervention) aims to make good this deficiency in the German Federal Republic by introducing nephropathy screening and a structured intervention to improve blood sugar and blood pressure regulation, optimizing lipid metabolism and nutritional intake. It was the aim of this study to assess with a computer-aided diabetes model the clinical value and cost-effectiveness of such an intervention.

PATIENTS AND METHODS

From data collected for 589 diabetics who participated in the PROSIT project, the short-time effects after one year on HbA1c, systolic blood pressure and lipid levels were obtained and cost-effectiveness compared with that of standard care. Life expectancy, life-time costs to be met by health insurance and event frequency of the diabetic nephropathy stages were calculated with a Markov model for type 2 diabetics.

RESULTS

PROSIT improved individual life expectancy by 0.23 years with reduction of life-time costs by DM 9,772 (ca. $4,900). The cumulative incidence of microalbuminuria was lowered by 30.5%, that of terminal renal failure by 55.9%. Even after discounting the results (i.e. the inclusion of time preference for cost and benefit) and stepwise changes of all variables by +/- 10%, PROSIT remained the more cost-effective variant.

CONCLUSION

From a health economy viewpoint PROSIT is superior to standard management. Early recognition of albuminuria and the introduction of a multifactorial treatment strategy make it possible to delay progression to terminal renal failure. In addition to its clinical benefits, prevention of dialysis and transplantation would reduce the annual savings of the health care system by several billion DM.

Prandial glucose regulation with repaglinide: its clinical and lifestyle impact in a large cohort of patients with Type 2 diabetes

OBJECTIVE

Prandial glucose regulation has the potential for achieving good metabolic control with a low risk of hypoglycaemia and increased flexibility with regard to eating patterns. Comparative studies have suggested that the prandial glucose regulator repaglinide is at least equivalent to sulphonylureas in terms of efficacy, but incurs a lower risk of major hypoglycaemia. However, these trials employed fixed dosing and mealtime regimens, so repaglinide was not used as intended. This prospective investigation in a daily clinical setting aimed to assess the efficacy and tolerability profile of flexible prandial glucose regulation with repaglinide in Type 2 diabetes.

DESIGN

5,985 patients with Type 2 diabetes in Germany were surveyed prospectively. These patients were assessed before and after a mean of 46 days treatment with repaglinide. At baseline, available data showed that 64% of patients had previously received therapy with conventional oral antidiabetic drugs, 22% were on diet alone, and 13% were naive to any treatment.

RESULTS

Overall, mean HbA1c decreased from 8.6 to 7.4%, fasting blood glucose from 183.9 to 134.2 mg/dl (10.2 to 7.4 mmol/l), blood glucose prior to main meals from 198.5 to 141.4 mg/dl (11 to 7.8 mmol/l), and blood glucose 2 hours after main meals from 219.3 mg/dl to 153.2 mg/dl (12.2 to 8.5 mmol/l). Subgroup analysis showed significant improvements in each of these parameters (P<0.0001) in therapy-naive patients, in patients switched from other oral antidiabetic drugs, and in patients receiving repaglinide as combination therapy. Body weight decreased slightly (1.2+/-2.7 kg). Only 49 hypoglycaemic episodes were reported, of which 38 cases were mild and no adverse sequelae to these events have been reported. Repaglinide also led to a liberating effect on lifestyle when patients were switched from other oral hypoglycaemic agents (OHAs), with 80% reporting a sense of relief at the prospect of being able to miss meals. The proportion of these patients reporting lifestyle restrictions as a result of fixed mealtimes declined from 36% to 7%. Before switching, 38% of the patients admitted to eating when not hungry for fear of hypoglycaemia, but only 10% continued this behaviour and patients took fewer supplementary snacks after switching to repaglinide.

CONCLUSION

Prandial glucose regulation with repaglinide improves metabolic control in patients with Type 2 diabetes without causing weight gain and with few hypoglycaemic episodes. This beneficial effect is seen in patients who are therapy-naive, have switched from alternative OHAs, or are in need of combination therapy. The prandial approach to treatment has a liberating effect with regard to eating behaviour that is welcomed by most patients switched from alternative therapies.

Vasopressin, major depression, and hypothalamic-pituitary-adrenocortical desensitization

BACKGROUND

The hypothalamic neuropeptide arginine vasopressin is thought to play an important role in the pathophysiology of affective disorders and the hyperactivity of the hypothalamic-pituitary-adrenocortical system that frequently accompanies them. Postmortem studies as well as clinical investigations have described elevated levels of vasopressin in the brain and plasma of depressed patients, and this finding has been suggested to contribute to depressive symptomatology.

METHODS

The case of a 47-year-old patient displaying chronically elevated plasma vasopressin levels due to paraneoplastic vasopressin secretion by an olfactory neuroblastoma and the first episode of major depression is presented.

RESULTS

Depressive symptoms improved markedly after surgical resection of the tumor and subsequent normalization of plasma vasopressin levels. Unexpectedly, neither corticotropin nor cortisol secretion could be stimulated by an intravenous corticotropin-releasing hormone challenge under the condition of chronically elevated plasma vasopressin levels in this patient.

CONCLUSIONS

Chronically elevated plasma vasopressin levels may induce depressive symptomatology, and-in contrast to the potent corticotropin secretagogue effects of acute vasopressin administration-lead to a marked desensitization of the hypothalamic-pituitary-adrenocortical system.

Attenuation of hypothalamic-pituitary-adrenal axis stress responses in late pregnancy: changes in feedforward and feedback mechanisms

The hypothalamic-pituitary-adrenal axis is hyporesponsive to stress in late pregnancy, exemplified as reduced adrenocorticotropic hormone (ACTH) and corticosterone responses to restraint, but the mechanisms are unknown. We investigated forward drive and negative feedback upon the hypothalamic-pituitary-adrenal axis in pregnant rats. Corticotropin-releasing hormone (CRH) and vasopressin mRNA expression in the parvocellular paraventricular nucleus and mineralocorticoid and glucocorticoid receptor expression in the paraventricular nucleus and hippocampus were quantified with in situ hybridization. Because it can enhance the corticosterone negative feedback signal, 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1) bioactivity in these brain regions and anterior pituitary was measured in vitro, and ACTH and corticosterone stress responses were measured after intracerebroventricular glycyrrhetinic acid, an 11beta-HSD inhibitor. Changes in corticosterone feedback on ACTH secretion were examined after pharmacological adrenalectomy by metyrapone and aminoglutethimide. Parvocellular paraventricular nucleus CRH mRNA content was reduced on day 21 and the CRH mRNA : vasopressin mRNA ratio was unaltered, indicating decreased production of both CRH and vasopressin. An increase in glucocorticoid receptor mRNA expression in the dentate gyrus (mineralocorticoid receptor mRNA expression was unaltered) and increased 11beta-HSD1 activity in the paraventricular nucleus and anterior pituitary suggest an increase in slow negative feedback mechanisms in pregnancy, but glycyrrhetinic acid did not modify the stress response. After metyrapone/aminoglutethimide treatment, corticosterone decreased ACTH secretion more slowly in pregnancy, indicating a decrease in rapid feedback sensitivity. Thus, reduced forward drive rather than increased effectiveness of glucocorticoid negative feedback may underlie stress hyporesponsiveness of the hypothalamic-pituitary-adrenal axis in pregnancy.

A single social defeat experience selectively stimulates the release of oxytocin, but not vasopressin, within the septal brain area of male rats

The naturally occurring social conflict situation to be confronted with an aggressive dominant conspecific was used to study the effects of emotional stress on the release of oxytocin (OXT) and arginine vasopressin (AVP) within the mediolateral septum of the rat brain. Male rats were chronically implanted with a microdialysis probe into this brain area. Local release patterns of both, OXT and AVP were monitored in response to a 30 min social defeat. Social defeat caused a significant increase in the release of OXT (to 254%+/-43%, P<0.01). In contrast, the release of AVP was not affected. In a preliminary experiment, to assess the physiological significance of stress-induced intraseptal OXT release, a separate group of animals received the OXT receptor antagonist des-Gly-NH(2)d(CH(2))(5)[Tyr(Me)(2)Thr(4)]OVT into the mediolateral septum via inverse microdialysis prior to and during the social defeat procedure. However, no difference could be observed in submissive freezing (passive coping) or in exploratory behavior (active coping) when compared to vehicle-treated animals, neither acutely nor 24 h after antagonist administration. Taken together, our results demonstrate that emotional stress activates the septal oxytocinergic, but not vasopressinergic, system. The physiological significance of intraseptally released OXT remains unclear and has to be elucidated in future studies.

Heregulin reverses the oligomerization of HER3

We analyzed the propensity of the HER3 receptor and its extracellular domain (ECD) to undergo ligand-independent self-association. The HER3-ECD, purified from Drosophila S2 cells, binds the EGF-like domain of heregulin (hrg) with a K(d) of 1.9 nM as measured by surface plasmon resonance (SPR) studies. In a gel shift assay, the HER3-ECD self-associates into a uniform, slowly migrating species in a concentration-dependent manner, starting at concentrations of <10 nM. In contrast to the HER3-ECD, the ECD from the related HER2 receptor does not oligomerize under the same conditions. The direct interaction of HER3-ECDs was also demonstrated by pull-down assays and SPR measurements under physiological salt conditions. This self-association of the HER3-ECD was reversed by the addition of hrg but not by EGF. The apparent equilibrium dissociation constant for the HER3-ECD self-association is 15 nM, based on SPR measurements. In this analysis, hrg blocks HER3-ECD self-association, and the addition of hrg during the dissociation phase resulted in an accelerated off rate. This finding suggests that hrg can bind to and disrupt preexisting HER3-ECD oligomers. Full-length HER3 likewise exhibited self-association. Under conditions where co-immunoprecipitation and cross-linking of HER2 and HER3 were stimulated by hrg, HER3 self-association and cross-linking were disrupted by hrg. The implication is that the self-association of HER3-ECD favors the formation of catalytically inactive complexes of the HER3 receptor. Binding of hrg releases HER3 which may then form signaling-competent HER3-HER2 heterodimers.

[Antidiabetic drug at every meal. Repaglinide is especially recommended for slender type 2 diabetic patients]

Repaglinide is the first stimulator of insulin secretion from the new meglitinide family. Via specific binding to the ATP-sensitive potassium channel of the beta cell membrane, it stimulates the rapid release of insulin. In preclinical studies, the insulin-stimulating effect of repaglinide has been found to be 10 to 20 times more potent than that of glibenclamide. Repaglinide is rapidly absorbed and has a short action, which makes it particularly well suited for the regulation of prandial blood glucose and meal-related dose adjustment. Since repaglinide is eliminated almost exclusively by non-renal routes, it can be used without danger in patients with moderately reduced renal function. Repaglinide is a suitable agent for first-line monotherapy in patients whose glucose metabolism cannot be optimally controlled by increasing physical activity and appropriate dietary measures. Repaglinide is clearly superior to glibenclamide in reducing postprandial hyperglycemia, and has a lower hypoglycemia risk than all the sulphonylureas. The flexibility of repaglinide makes it possible for good oral meal-related treatment.

Verapamil prevents withdrawal excitation of oxytocin neurones in morphine-dependent rats

We investigated whether the full expression of morphine withdrawal excitation by supraoptic nucleus (SON) oxytocin neurones is a property of the neurones themselves or a partial function of their afferent inputs, by interrupting synaptic input activity via central administration of the L-type Ca(2+) channel blocker verapamil. In morphine-dependent rats, withdrawal-induced release of oxytocin from the posterior pituitary was suppressed by prior administration of intracerebroventricular (i.c.v.) verapamil (160 microg), as was release of oxytocin within the SON measured by microdialysis. During morphine withdrawal the increased electrical activity of SON neurones was also reduced both by i.c.v. verapamil and microdialysis application of verapamil or nifedipine into the SON. Oxytocin secretion evoked by electrical stimulation of the pituitary stalk was unaffected by i.c.v. verapamil suggesting a central site of action. To determine whether the inhibitory actions of verapamil were specific to morphine withdrawal, we also investigated the effects of verapamil on other oxytocin-secreting stimuli. I.C.V. verapamil given to morphine-naïve rats abolished pituitary oxytocin release in response to activation of brainstem or rostral excitatory inputs by cholecystokinin (20 microg kg(-1), i.v.) and 1.5 M saline (4 ml kg(-1), i.p.) respectively, whilst in lactating rats, i.c.v. verapamil reduced suckling-induced release of oxytocin within the SON. These results suggest that verapamil has a central site of action on stimulated oxytocin release (including an action within the SON) and that both pre and post-synaptic L-type Ca(2+) channels are required for the full expression of morphine withdrawal in SON oxytocin neurones.

Human ERK1 induces filamentous growth and cell wall remodeling pathways in Saccharomyces cerevisiae

Expression of an activated extracellular signal-regulated kinase 1 (ERK1) construct in yeast cells was used to examine the conservation of function among mitogen-activated protein (MAP) kinases. Sequence alignment of the human MAP kinase ERK1 with all Saccharomyces cerevisiae kinases reveals a particularly strong kinship with Kss1p (invasive growth promoting MAP kinase), Fus3p (pheromone response MAP/ERK kinase), and Mpk1p (cell wall remodeling MAP kinase). A fusion protein of constitutively active human MAP/ERK kinase 1 (MEK) and human ERK1 was introduced under regulated expression into yeast cells. The fusion protein (MEK/ERK) induced a filamentation response element promoter and led to a growth retardation effect concomitant with a morphological change resulting in elongated cells, bipolar budding, and multicell chains. Induction of filamentous growth was also observed for diploid cells following MEK/ERK expression in liquid culture. Neither haploids nor diploids, however, showed marked penetration of agar medium. These effects could be triggered by either moderate MEK/ERK expression at 37 degrees C or by high level MEK/ERK expression at 30 degrees C. The combination of high level MEK/ERK expression and 37 degrees C resulted in cell death. The deleterious effects of MEK/ERK expression and high temperature were significantly mitigated by 1 m sorbitol, which also enhanced the filamentous phenotype. MEK/ERK was able to constitutively activate a cell wall maintenance reporter gene, suggesting misregulation of this pathway. In contrast, MEK/ERK effectively blocked expression from a pheromone-responsive element promoter and inhibited mating. These results are consistent with MEK/ERK promoting filamentous growth and altering the cell wall through its ability to partially mimic Kss1p and stimulate a pathway normally controlled by Mpk1p, while appearing to inhibit the normal functioning of the structurally related yeast MAP kinase Fus3p.

Repetitive transcranial magnetic stimulation induces active coping strategies and attenuates the neuroendocrine stress response in rats

The effects of repetitive transcranial magnetic stimulation (rTMS) on various brain functions were investigated in adult male Wistar rats. The stimulation parameters were adjusted according to the results of accurate computer-assisted, magnetic resonance imaging-based reconstructions of the current density distributions induced by rTMS in the rat and human brain, ensuring comparable stimulation patterns in both cases. The animals were subjected to daily rTMS-treatment (three trains of 20 Hz; 2.5 s) for 8 weeks from the age of 4 weeks on. In the forced swim test these rats showed a more active stress coping strategy than the control rats. This was accompanied by a significantly attenuated stress-induced elevation of plasma ACTH concentrations. Pituitary changes accounting for the attenuation were ruled out by the corticotropin-releasing hormone test. Baseline concentrations of ACTH and corticosterone were indistinguishable in the two groups. No changes were found in the anxiety-related behavior of the rats on the elevated plus-maze or in behavior during the social interaction test. Accordingly, the binding characteristics of the benzodiazepine agonist [(3)H]flunitrazepam at the benzodiazepine/gamma-aminobutyric acid type A receptor complex were similar in the rTMS and control groups. In summary, chronic rTMS treatment of frontal brain regions in rats resulted in a change in coping strategy that was accompanied by an attenuated neuroendocrine response to stress, thus revealing parallels to the effects of antidepressant drug treatment.

Pharmacological characterisation of cortical gamma-aminobutyric acid type A (GABAA) receptors in two Wistar rat lines selectively bred for high and low anxiety-related behaviour

Two Wistar rat lines that have been selectively bred for high-anxiety-related behaviour (HAB) and low-anxiety-related behaviour (LAB) in the elevated plusmaze test may be considered as a genetically prone animal model to study the neurochemical correlates of anxiety-related behaviour. Because there are pronounced differences between the two lines both in baseline levels of open-arm exploration in the elevated plus-maze test and in sensitivity to the anxiolytic effects of 1 mg/kg diazepam, we used these lines to investigate the pharmacology of the benzodiazepine binding site and the GABA binding site of cortical GABAA receptors. No difference in characteristics of flunitrazepam, zolpidem or muscimol binding to cortical GABAA receptors could be detected between the two lines. Although there was an increase in the brain concentration of the anxiolytic neuroactive steroid allopregnanolone, a potent positive allosteric modulator of GABAA receptors, both in HAB and LAB animals after a forced swim stress, allopregnanolone concentrations did not differ between the two lines. Moreover, plasma dehydroepiandrosterone (DHEA) concentrations were similar in HAB and LAB animals. We conclude that anxiety-related behaviour and benzodiazepine sensitivity in these rat lines are likely to be independent of the pharmacology of cortical GABAA receptors.

Unconditioned anxiety and social behaviour in two rat lines selectively bred for high and low anxiety-related behaviour

Individuals of high anxiety-related behaviour (HAB) and low anxiety-related behaviour (LAB) rat lines were selectively bred for differences in anxiety-related behaviour on the elevated plus-maze. The goal of this study was to investigate whether this behavioural difference is restricted to the test used as the selection criterion or whether it is a stable and robust trait also in other conflict or non-conflict situations. Therefore, behaviour of male and female HAB and LAB rats was examined in two further tests of unconditioned anxiety: the black-white box and the social interaction test. Furthermore, behaviour of group-housed male HAB and LAB rats was studied in their home cages. In addition to standard statistics, discriminant analyses were performed. The difference in anxiety-related behaviour between the two lines was highly consistent in all tests of unconditioned anxiety. There were also differences in home cage behaviour, LAB rats being more active than HAB rats; this is likely to be a consequence of the LAB rats displaying a higher aggressiveness in social behaviour, compared to HAB rats. In all tests used HAB and LAB rats were clearly distinguished by discriminant analysis. However, while in the elevated plus-maze and the black-white box test the most important parameters for discrimination between the two lines were mainly those generally seen as closely related to anxiety, the discrimination in the social interaction paradigm was primarily due to differences in locomotor activity.

[Therapy of type 2 diabetes. Critical evaluation of oral antidiabetic drugs]

Changes in lifestyle and eating habits always form the initial phase of treatment of type 2 diabetes. Sooner or later, type 2 diabetes is associated with a lack of insulin that makes treatment with insulin necessary. Today, however, modern oral antidiabetics make it possible to exert a selective positive influence on both insulin resistance and disturbed insulin secretion. Three main groups of substances are available. Among the stimulators of insulin secretion are the sulfonylureas (e.g. glibenclamide, glibonuride, glisoxepid, glimepiride), and the so-called prandial glucose regulators, such as repaglinide, which differ from the sulfonylureas both chemically and in their pharmacodynamic properties. The group of insulin sensitizers includes the biguanide, metformin and the thiazolidinediones or glitazones (rosiglitazone, pioglitazone). The third group are the alpha-glucosidase inhibitors, e.g. acarbose. In principle, these oral antidiabetics can be combined with one another.

Ageing alters intrahypothalamic release patterns of vasopressin and oxytocin in rats

The ageing process has been shown to have a profound impact on the hypothalamo-neurohypophysial system (HNS) and the hypothalamo-pituitary-adrenocortical (HPA) axis in humans as well as in rodents. Therefore, in this study, the intracerebral and peripheral release patterns of both vasopressin and oxytocin have been studied in aged male Wistar rats under basal conditions and in response to ethologically relevant stressors, using intracerebral microdialysis and chronic blood sampling techniques, respectively. Approximately a twofold higher basal release of arginine vasopressin (AVP) within the hypothalamic paraventricular nucleus (PVN), but not within the supraoptic nucleus (SON), was found in aged rats, whereas basal oxytocin (OXT) release did not differ in comparison with young rats. With increasing age the rise in intra-PVN release of both AVP and OXT was blunted in response to forced swimming. In contrast, the intra-SON release of AVP was unrelated to age. Simultaneously recorded basal secretion of both AVP and OXT from the neurohypophysis into blood was increased in aged rats, with a blunted OXT response to swim stress. Opposed to that, plasma AVP levels remained unchanged in both groups. Basal plasma levels of corticotropin (ACTH) and corticosterone were elevated in aged rats, whereas stress-elicited ACTH and corticosterone responses were indistinguishable. These results indicate age-related changes in the HNS and HPA axis with an enhanced basal activity opposed to a blunted response to stressors with increasing age. The increased basal release of AVP within the PVN suggests a role of intracerebral AVP in age-associated alterations of HPA axis regulation.