Orphanin FQ acts as an anxiolytic to attenuate behavioral responses to stress

Orphanin FQ (OFQ, Nociceptin) is a recently discovered 17-amino acid neuropeptide that is structurally related to the opioid peptides but does not bind opioid receptors. OFQ has been proposed to act as an anti-opioid peptide, but its widespread sites of action in the brain suggest that it may have more general functions. Here we show that OFQ plays an important role in higher brain functions because it can act as an anxiolytic to attenuate the behavioral inhibition of animals acutely exposed to stressful/anxiogenic environmental conditions. OFQ anxiolytic-like effects were consistent across several behavioral paradigms generating different types of anxiety states in animals (light-dark preference, elevated plus-maze, exploratory behavior of an unfamiliar environment, pharmacological anxiogenesis, operant conflict) and were observed at low nonsedating doses (0.1–3 nmol, intracerebroventricular). Like conventional anxiolytics, OFQ interfered with regular sensorimotor function at high doses (>3 nmol). Our results show that an important role of OFQ is to act as an endogenous regulator of acute anxiety responses. OFQ, probably in concert with other major neuropeptides, exerts a modulatory role on the central integration of stressful stimuli and, thereby, may modulate anxiety states generated by acute stress.

Prenatal stress produces learning deficits associated with an inhibition of neurogenesis in the hippocampus

Early experiences such as prenatal stress significantly influence the development of the brain and the organization of behavior. In particular, prenatal stress impairs memory processes but the mechanism for this effect is not known. Hippocampal granule neurons are generated throughout life and are involved in hippocampal-dependent learning. Here, we report that prenatal stress in rats induced lifespan reduction of neurogenesis in the dentate gyrus and produced impairment in hippocampal-related spatial tasks. Prenatal stress blocked the increase of learning-induced neurogenesis. These data strengthen pathophysiological hypotheses that propose an early neurodevelopmental origin for psychopathological vulnerabilities in aging.

Arabidopsis Roots and Shoots Have Different Mechanisms for Hypoxic Stress Tolerance

Arabidopsis has inducible responses for tolerance of O2 deficiency. Plants previously exposed to 5% O2 were more tolerant than the controls to hypoxic stress (0.1% O2 for 48 h) in both roots and shoots, but hypoxic acclimation did not improve tolerance to anoxia (0% O2). The acclimation of shoots was not dependent on the roots: increased shoot tolerance was observed when the roots of the plants were removed. An adh (alcohol dehydrogenase) null mutant did not show acclimation of the roots but retained the shoot survival response. Abscisic acid treatment also differentiated the root and shoot responses; pretreatment induced root survival in hypoxic stress conditions (0.1% O2) but did not induce any increase in the survival of shoots. Cycloheximide blocked both root and shoot acclimation, indicating that both acclimation mechanisms are dependent on protein synthesis.

Light and Excess Manganese1 : Implications for Oxidative Stress in Common Bean

The effect of light intensity on antioxidants, antioxidant enzymes, and chlorophyll content was studied in common bean (Phaseolus vulgaris L.) exposed to excess Mn. Leaves of bean genotypes contrasting in Mn tolerance were exposed to two different light intensities and to excess Mn; light was controlled by shading a leaflet with filter paper. After 5 d of Mn treatment ascorbate was depleted by 45% in leaves of the Mn-sensitive genotype ZPV-292 and by 20% in the Mn-tolerant genotype CALIMA. Nonprotein sulfhydryl groups and glutathione reductase were not affected by Mn or light treatment. Ten days of Mn-toxicity stress increased leaf ascorbate peroxidase activity of cv ZPV-292 by 78% in low light and by 235% in high light, and superoxide dismutase activity followed a similar trend. Increases of ascorbate peroxidase and superoxide dismutase activity observed in cv CALIMA were lower than those observed in the susceptible cv ZPV-292. The cv CALIMA had less ascorbate oxidation under excess Mn-toxicity stress. Depletion of ascorbate occurred before the onset of chlorosis in Mn-stressed plants, especially in cv ZPV-292. Lipid peroxidation was not detected in floating leaf discs of mature leaves exposed to excess Mn. Our results suggest that Mn toxicity may be mediated by oxidative stress, and that the tolerant genotype may maintain higher ascorbate levels under stress than the sensitive genotype.

Osmotic Stress Induces Expression of Choline Monooxygenase in Sugar Beet and Amaranth1

Choline monooxygenase (CMO) catalyzes the committing step in the synthesis of glycine betaine, an osmoprotectant accumulated by many plants in response to salinity and drought. To investigate how these stresses affect CMO expression, a spinach (Spinacia oleracea L., Chenopodiaceae) probe was used to isolate CMO cDNAs from sugar beet (Beta vulgaris L., Chenopodiaceae), a salt- and drought-tolerant crop. The deduced beet CMO amino acid sequence comprised a transit peptide and a 381-residue mature peptide that was 84% identical (97% similar) to that of spinach and that showed the same consensus motif for coordinating a Rieske-type [2Fe-2S] cluster. A mononuclear Fe-binding motif was also present. When water was withheld, leaf relative water content declined to 59% and the levels of CMO mRNA, protein, and enzyme activity rose 3- to 5-fold; rewatering reversed these changes. After gradual salinization (NaCl:CaCl2 = 5.7:1, mol/mol), CMO mRNA, protein, and enzyme levels in leaves increased 3- to 7-fold at 400 mm salt, and returned to uninduced levels when salt was removed. Beet roots also expressed CMO, most strongly when salinized. Salt-inducible CMO mRNA, protein, and enzyme activity were readily detected in leaves of Amaranthus caudatus L. (Amaranthaceae). These data show that CMO most probably has a mononuclear Fe center, is inducibly expressed in roots as well as in leaves of Chenopodiaceae, and is not unique to this family.

The effects of stress on social preferences are sexually dimorphic in prairie voles.

Prairie voles (Microtus ochrogaster) are monogamous rodents that form pair bonds characterized by a preference for a familiar social partner. In male prairie voles, exposure to either the stress of swimming or exogenous injections of corticosterone facilitate the development of a social preference for a female with which the male was paired after injection or swimming. Conversely, adrenalectomy inhibits partner preference formation in males and the behavioral effects of adrenalectomy are reversed by corticosterone replacement. In female prairie voles, swim stress interferes with the development of social preferences and corticosterone treatments inhibit the formation of partner preferences, while adrenalectomized females form preferences more quickly than adrenally intact controls. Because sex differences in both behavior and physiology are typically reduced in monogamous species, we initially predicted that male and female prairie voles would exhibit similar behavioral responses to corticosterone. However, our findings suggest an unanticipated sexual dimorphism in the physiological processes modulating social preferences. This dimorphic involvement of stress hormones in pair bonding provides a proximate mechanism for regulating social organization, while permitting males and females to adapt their reproductive strategies in response to environmental challenges.

Characterization of Arabidopsis thaliana cDNAs that render yeasts tolerant toward the thiol-oxidizing drug diamide.

Diamide oxidizes cellular thiols and induces oxidative stress. To isolate plant genes which may, when overexpressed, increase tolerance of plants toward oxidative damage, an in vivo diamide tolerance screening in yeasts was used. An Arabidopsis cDNA library in a yeast expression vector was used to transform a yeast strain with intact antioxidant defense. Cells from approximately 10(5) primary transformants were selected for resistance to diamide. Three Arabidopsis cDNAs which confer diamide tolerance were isolated. This drug tolerance was specific and no cross tolerance toward hydroperoxides was found. One cDNA (D3) encodes a polypeptide which has an amino-terminal J domain characteristic of a divergent family of DnaJ chaperones. Another (D18) encodes a putative dTDP-D-glucose 4,6-dehydratase. Surprisingly, the third cDNA (D22) encodes a plant homolog of gamma-glutamyltransferases. It would have been difficult to predict that the expression of those genes would lead to an improved survival under conditions of depletion of cellular thiols. Hence, we suggest that this cloning approach may be a useful contribution to the isolation of plant genes that can help to cope with oxidative stress.