Gastrectomy alters emotional reactivity in rats: neurobiological mechanisms.

Gastrectomy (Gsx) is associated with altered emotional function and a predisposition to depression/anxiety disorders. Here we investigated the effects of Gsx on emotional reactivity in rats and explored the underlying neurobiological mechanisms. Gsx- and sham-operated rats were exposed to behavioural tests that explore anxiety- and depression-like behaviour (open field, black and white box, elevated plus maze, social interaction, forced swim) as well as memory (object recognition).

Ghrelin increases intake of rewarding food in rodents.

We investigated whether ghrelin action at the level of the ventral tegmental area (VTA), a key node in the mesolimbic reward system, is important for the rewarding and motivational aspects of the consumption of rewarding/palatable food. Mice with a disrupted gene encoding the ghrelin receptor (GHS-R1A) and rats treated peripherally with a GHS-R1A antagonist both show suppressed intake of rewarding food in a free choice (chow/rewarding food) paradigm. Moreover, accumbal dopamine release induced by rewarding food was absent in GHS-R1A knockout mice.

Central NMU signaling in body weight and energy balance regulation: evidence from NMUR2 deletion and chronic central NMU treatment in mice.

To investigate the role of the central neuromedin U (NMU) signaling system in body weight and energy balance regulation, we examined the effects of long-term intracerebroventricular (icv) infusion of NMU in C57Bl/6 mice and in mice lacking the gene encoding NMU receptor 2. In diet-induced obese male and female C57BL/6 mice, icv infusion of NMU (8 microg x day(-1) x mouse(-1)) for 7 days decreased body weight and total energy intake compared with vehicle treatment. However, these parameters were unaffected by NMU treatment in lean male and female C57BL/6 mice fed a standard diet.

Requirement of central ghrelin signaling for alcohol reward.

The stomach-derived hormone ghrelin interacts with key CNS circuits regulating energy balance and body weight. Here we provide evidence that the central ghrelin signaling system is required for alcohol reward. Central ghrelin administration (to brain ventricles or to tegmental areas involved in reward) increased alcohol intake in a 2-bottle (alcohol/water) free choice limited access paradigm in mice.

Anorexigenic and electrophysiological actions of novel ghrelin receptor (GHS-R1A) antagonists in rats.

Here we provide the first pharmacological exploration of the impact of acute central nervous system exposure to three recently developed ghrelin receptor (GHS-R1A) ligands on food intake and on the electrical activity of the target cells for ghrelin in the hypothalamus. Central (i.c.

Prenatal stress alters the negative correlation between neuronal activation in limbic regions and behavioral responses in rats exposed to high and low anxiogenic environments.

Behavioral adaptation to an anxiogenic environment involves the activity of various interconnected limbic regions, such as the amygdala, hippocampus and prefrontal cortex. Prenatal stress (PS) in rats affects the ability to cope with environmental challenges and alters brain plasticity, leading to long-lasting behavioral and neurobiological alterations. We examined in PS and control animals whether behavioral reactivity was correlated to neuronal activation by assessing Fos protein expression in limbic regions of rats exposed to a low or high anxiogenic environment (the closed and open arms of an elevated plus maze, respectively).

Confinement to the open arm of the elevated-plus maze as anxiety paradigm: behavioral validation.

Exposure to the open arm of the elevated-plus maze was used to assess the neurobiological correlates of anxiety in the high-anxiety-related behavior (HAB) and low-anxiety-related behavior (LAB) rat lines. The authors sought to determine whether this mild stressor could be considered a valuable anxiety test revealing specific behavioral differences. Behavioral parameters scored were submitted to a discriminant and factor analysis to investigate emotional parameters discriminating HAB and LAB rats.

Altered hypothalamo-pituitary-adrenal and sympatho-adrenomedullary activities in rats bred for high anxiety: central and peripheral correlates.

Wistar rats have been selectively bred for high (HABs) or low (LABs) anxiety-related behavior based on results obtained in the elevated-plus maze. They also display robust behavioral differences in a variety of additional anxiety tests. The present study was undertaken to further characterize physiological substrates that contribute to the expression of this anxious trait.

Genetic predisposition to anxiety-related behavior determines coping style, neuroendocrine responses, and neuronal activation during social defeat.

Genetic background may influence an individual's susceptibility to, and subsequent coping strategy for, an acute stressor. When exposed to social defeat (SD), rats bred for high (HAB) or low (LAB) trait anxiety, which also differ in depression-like behavior, showed highly divergent passive and active coping behaviors, respectively. HABs spent more time freezing and emitted more ultrasound vocalization calls during SD than LABs, which spent more time rearing and grooming.

Evidence that the lateral septum is involved in the antidepressant-like effects of the vasopressin V1b receptor antagonist, SSR149415.

Previous experiments with the first selective nonpeptide vasopressin V1b receptor antagonist SSR149415 ((2S, 4R)-1-[5-chloro-1-[(2,4-dimethoxyphenyl)sulfonyl]-3-(2-methoxyphenyl)-2-oxo-2,3-dihydro-1H-indol-3-yl]-4-hydroxy-N,N-dimethyl-2-pyrrolidinecarboxamide) have shown that the drug elicits anxiolytic- and antidepressant-like effects following systemic administration. Extrahypothalamic V1b receptors have been suggested to be involved in these effects as evidenced by the findings that hypophysectomized rats were still sensitive to the antistress action of SSR149415. The first objective of the present work aimed at locating V1b receptors in the rat limbic brain using anti-V1b receptor immunohistochemistry.

High trait anxiety and hyporeactivity to stress of the dorsomedial prefrontal cortex: a combined phMRI and Fos study in rats.

The neural basis of trait anxiety is poorly understood. In genetically selected hyperanxious (high anxiety-related behavior; HAB) rats, diazepam induces a stronger anxiolytic response than in hypoanxious (low anxiety-related behavior; LAB) rats. A screen for neuronal response differences to diazepam between HAB and LAB rats using pharmacologic fMRI (phMRI) at 7 T revealed a blunted diazepam-induced neuronal deactivation in the dorsomedial prefrontal cortex (dmPFC) of HABs.

Neurobiological correlates of high (HAB) versus low anxiety-related behavior (LAB): differential Fos expression in HAB and LAB rats.

Background: Two Wistar rat lines selectively bred for either high (HAB) or low (LAB) anxiety-related behavior were used to identify neurobiological correlates of trait anxiety.

Methods: We used Fos expression for mapping of neuronal activation patterns in response to mild anxiety-provoking challenges.

Results: In both lines, exposure to an open field (OF) or the open arm (OA) of an elevated plus-maze induced Fos expression in several brain areas of the anxiety/fear circuitry.

Reliability of high and low anxiety-related behaviour: influence of laboratory environment and multifactorial analysis.

The reliability of behavioural data constitutes a major concern in the neuroscience field. Indeed, discrepancies in the behavioural patterns of mice or rats in the same anxiety tests performed in different laboratories have been reported recently. The question raised by such data addressed, in particular, the selection and breeding of two lines of rats on the basis of their high (HAB) and low (LAB) anxiety-related behaviour in the elevated plus-maze test at the Max Planck Institute of Psychiatry in Munich (Germany).