Substance P excites GABAergic neurons in the mouse central amygdala through neurokinin 1 receptor activation.

Substance P (SP) is implicated in stress regulation and affective and anxiety-related behavior. Particularly high expression has been found in the main output region of the amygdala complex, the central amygdala (CE). Here we investigated the cellular mechanisms of SP in CE in vitro, taking advantage of glutamic acid decarboxylase-green fluorescent protein (GAD67-GFP) knockin mice that yield a reliable labeling of GABAergic neurons, which comprise 95% of the neuronal population in the lateral section of CE (CEl). In GFP-positive neurons within CEl, SP caused a membrane depolarization and increase in input resistance, associated with an increase in action potential firing frequency. Under voltage-clamp conditions, the SP-specific membrane current reversed at -101.5 ± 2.8 mV and displayed inwardly rectifying properties indicative of a membrane K(+) conductance. Moreover, SP responses were blocked by the neurokinin type 1 receptor (NK1R) antagonist L-822429 and mimicked by the NK1R agonist [Sar(9),Met(O2)(11)]-SP. Immunofluorescence staining confirmed localization of NK1R in GFP-positive neurons in CEl, predominantly in PKCδ-negative neurons (80%) and in few PKCδ-positive neurons (17%). Differences in SP responses were not observed between the major types of CEl neurons (late firing, regular spiking, low-threshold bursting). In addition, SP increased the frequency and amplitude of GABAergic synaptic events in CEl neurons depending on upstream spike activity. These data indicate a NK1R-mediated increase in excitability and GABAergic activity in CEl neurons, which seems to mostly involve the PKCδ-negative subpopulation. This influence can be assumed to increase reciprocal interactions between CElon and CEloff pathways, thereby boosting the medial CE (CEm) output pathway and contributing to the anxiogenic-like action of SP in the amygdala.

Pleurotus biomass production on vinasse and its potential use for aquaculture feed.

The vinasse is a by-product generated during the manufacture of alcohol from sugarcane fermentation. Rich in organic matter, it is known that the vinasse has the potential to be used as a source of nutrients for plants as well as microorganisms. In this study, the fungi Pleurotus sajor-caju, P. ostreatus, P. albidus and P. flabellatus were cultivated in vinasse and utilised as a complementary diet for Danio rerio fish. The fungi mycelia cultured in vinasse for 15 days were lyophilised and offered to the fishes at a rate of 2% (medium/body weight) for 28 days. P. albidus produced the highest biomass (16.27 g L-1). Bromatological analysis of mycelia showed similar values to commercial rations. Toxicity tests showed that fish survival was 100% and no significant biomass loss was observed, indicating that the tested fungi grown in vinasse showed no toxicity. Our results showed that vinasse is a promising by-product for fungal growth and the mycelia of Pleurotus sp. fungi can be included in the diets of fish as a nutritional supplement.

Anxiety- rather than depression-like behavior is associated with adult neurogenesis in a female mouse model of higher trait anxiety- and comorbid depression-like behavior.

Adult neurogenesis has been implicated in affective disorders and the action of antidepressants (ADs) although the functional significance of this association is still unclear. The use of animal models closely mimicking human comorbid affective and anxiety disorders seen in the majority of patients should provide relevant novel information. Here, we used a unique genetic mouse model displaying higher trait anxiety (HAB) and comorbid depression-like behavior. We demonstrate that HABs have a lower rate of hippocampal neurogenesis and impaired functional integration of newly born neurons as compared with their normal anxiety/depression-like behavior (NAB) controls. In HABs, chronic treatment with the AD fluoxetine alleviated their higher depression-like behavior and protected them from relapse for 3 but not 7 weeks after discontinuation of the treatment without affecting neurogenesis. Similar to what has been observed in depressed patients, fluoxetine treatment induced anxiogenic-like effects during the early treatment phase in NABs along with a reduction in neurogenesis. On the other hand, treatment with AD drugs with a particularly strong anxiolytic component, namely the neurokinin-1-receptor-antagonist L-822 429 or tianeptine, increased the reduced rate of neurogenesis in HABs up to NAB levels. In addition, challenge-induced hypoactivation of dentate gyrus (DG) neurons in HABs was normalized by all three drugs. Overall, these data suggest that AD-like effects in a psychopathological mouse model are commonly associated with modulation of DG hypoactivity but not neurogenesis, suggesting normalization of hippocampal hypoactivity as a neurobiological marker indicating successful remission. Finally, rather than to higher depression-related behavior, neurogenesis seems to be linked to pathological anxiety.

Magnesium deficiency induces anxiety and HPA axis dysregulation: modulation by therapeutic drug treatment.

Preclinical and some clinical studies suggest a relationship between perturbation in magnesium (Mg(2+)) homeostasis and pathological anxiety, although the underlying mechanisms remain largely unknown. Since there is evidence that Mg(2+) modulates the hypothalamic-pituitary adrenal (HPA) axis, we tested whether enhanced anxiety-like behaviour can be reliably elicited by dietary Mg(2+) deficiency and whether Mg(2+) deficiency is associated with altered HPA axis function. Compared with controls, Mg(2+) deficient mice did indeed display enhanced anxiety-related behaviour in a battery of established anxiety tests. The enhanced anxiety-related behaviour of Mg(2+) deficient mice was sensitive to chronic desipramine treatment in the hyponeophagia test and to acute diazepam treatment in the open arm exposure test. Mg(2+) deficiency caused an increase in the transcription of the corticotropin releasing hormone in the paraventricular hypothalamic nucleus (PVN), and elevated ACTH plasma levels, pointing to an enhanced set-point of the HPA axis. Chronic treatment with desipramine reversed the identified abnormalities of the stress axis. Functional mapping of neuronal activity using c-Fos revealed hyper-excitability in the PVN of anxious Mg(2+) deficient mice and its normalisation through diazepam treatment. Overall, the present findings demonstrate the robustness and validity of the Mg(2+) deficiency model as a mouse model of enhanced anxiety, showing sensitivity to treatment with anxiolytics and antidepressants. It is further suggested that dysregulations in the HPA axis may contribute to the hyper-emotionality in response to dietary induced hypomagnesaemia. This article is part of a Special Issue entitled 'Anxiety and Depression'.

Altered GABA transmission in a mouse model of increased trait anxiety.

Anxiety disorders are the most prevalent central nervous system diseases imposing a high social burden to our society. Emotional processing is particularly controlled by GABA-ergic transmission in the amygdala. Using in situ hybridization and immunohistochemistry we now investigated changes in the expression of GABA synthesizing enzymes (GAD65 and GAD67), GABA(A) (α1-5, ß1-3, γ1-2) and GABA(B) receptor subunits (GBBR1, GBBR2) in amygdaloid nuclei of high anxiety-related behavior (HAB) mice in comparison to mice selected for normal anxiety-related behavior (NAB). Levels of GAD65 and GAD67 mRNAs and protein, as well as those of GABA were increased in the amygdala of HAB mice. Relative to NAB controls, mRNA expression of the GABA(A) receptor subunits ß1, ß2 and γ2 was specifically increased in the basolateral amygdala of HAB mice while transcription of α5 and γ1 subunits was reduced in the central and medial amygdala. On the protein level, increases in ß2 and γ2 subunit immunoreactivities were evident in the basolateral amygdala of HAB mice. No change in GABA(B) receptor expression was observed. These findings point towards an imbalanced GABA-ergic neurotransmission in the amygdala of HAB mice. On the other hand, FosB, a marker for neuronal activity, was increased in principal neurons of the basolateral amygdala in HAB mice, reflecting activation of excitatory neurons, possibly as a consequence of reduced GABA-ergic tonic inhibition through α5 and γ1 containing receptors. Ultimately these mechanisms may lead to the compensatory activation of GABA transmission, as indicated by the increased expression of GAD65/67 in HAB mice.

Genetic functional inactivation of neuronal nitric oxide synthase affects stress-related Fos expression in specific brain regions.

To identify neuronal substrates involved in NO/stress interactions we used Fos expression as a marker and examined the pattern of neuronal activation in response to swim stress in nNOS knock-out (nNOS-/-) and wild-type (WT) mice. Forced swimming enhanced Fos expression in WT and nNOS-/- mice in several brain regions, including cortical, limbic and hypothalamic regions. Differences in the Fos response between the two groups were observed in a limited set (6 out of 42) of these brain areas only: nNOS-/- mice displayed increased stressor-induced Fos expression in the medial amygdala, periventricular hypothalamic nucleus, supraoptic nucleus, CA1 field of the hippocampus, dentate gyrus and infralimbic cortex. No differences were observed in regions including the septum, central amygdala, periaqueductal grey and locus coeruleus. During forced swimming, nNOS-/- mice displayed reduced immobility duration, while no differences in general locomotor activity were observed between the groups in the home cage and during the open field test. The findings indicate that deletion of nNOS alters stress-coping ability during forced swimming and leads to an altered pattern of neuronal activation in response to this stressor in specific parts of the limbic system, hypothalamus and the medial prefrontal cortex.

Evaluation of the effect of chronic antidepressant treatment on neurokinin-1 receptor expression in the rat brain.

Clinically effective antidepressants are thought to exert their therapeutic effects by facilitating central monoamine neurotransmission. However, recent data showing that neurokinin-1 receptor (NK1R) antagonists have antidepressant properties in both animal and clinical studies raise the possibility that classical antidepressants may also influence NK1R expression in the brain. To test this hypothesis, rats were treated with desipramine, paroxetine, venlafaxine, tranylcypromine or vehicle for 14-42 days. NK1R binding sites and mRNA were determined in a wide variety of brain areas using in situ hybridization and quantitative receptor autoradiography. In all areas examined, the abundance of NK1R binding sites was unchanged after 14 days of treatment. None of the treatments altered the number of NK1R binding sites following 42 days treatment with the exception that an increase was found in the locus coeruleus with tranylcypromine. Taken together, we report that repeated treatment with antidepressants of different classes does not cause significant changes in NK1R expression.