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Increase in dopamine metabolites in rat brain by neurotensin
Neurotensin (NT), an endogenous tridecapeptide, is heterogeneously distributed in the central nervous system. The present study examined the effects of physiologically and behaviorally active doses of NT (1--100 micrograms intracisternally) on dopamine, serotonin and their primary metabolites as well as accumulation of dopa after inhibition of dopa decarboxylase. NT was shown to increase dopa accumulation when compared with saline treatment, suggesting that dopamine synthesis was increased. In accord with this view, NT also caused a dose-dependent increase in homovanillic acid and dihydroxyphenylacetic acid, the major metabolites of dopamine, in several brain areas (striatum, olfactory tubercles, nucleus accumbens, frontal cortex and hypothalamus). Interestingly, the increase in homovanillic acid was greater than that for dihydroxyphenylacetic acid. In striatum, an initial increase in dopamine content after 30 micrograms of NT was followed by an increase and a subsequent decrease of dopamine metabolites. Several other neuropeptides (Met-enkephalin, cholecystokinin-8, thyrotropin releasing hormone, substance P and d-Arg9-NT), at doses equimolar to 30 micrograms of NT, did not affect dopamine metabolites, whereas certain others (beta-endorphin and bombesin) increased their concentration in some brain areas. Except for the highest dose of NT, measures of serotonergic function were not affected by NT or any of the other neuropeptides
Acorn consumption improves the immune response of the dung beetle Thorectes lusitanicus
Thorectes lusitanicus, a typically coprophagous species is also actively attracted to oak acorns, consuming, burying them, and conferring ecophysiological and reproductive advantages to both the beetle and the tree. In this study, we explored the possible relation between diet shift and the health status of T. lusitanicus using a generalist entomopathogenic fungus (Metarhizium anisopliae) as a natural pathogen. To measure the health condition and immune response of beetles, we analysed the protein content in the haemolymph, prophenoloxidase (proPO) content, phenoloxidase (PO) activity and mortality of beetles with diets based on either acorns or cow dung. Protein content, proPO levels and PO levels in the haemolymph of T. lusitanicus were found to be dependent on the type of diet. Furthermore, the beetles fed with acorns developed a more effective proPO-PO system than the beetles fed with cow dung. Furthermore, a significant decrease in mortality was observed when infected individuals were submitted to an acorn-based diet. In addition to enhancing an understanding of the relevance of dietary change to the evolutionary biology of dung beetles, these results provide a more general understanding of the ecophysiological implications of differential dietary selection in the context of fitness.Financial support was provided by the Projects CGL2008/03878/BOS and CGL2011-25544 of the Secretaría de Estado de Investigación-Ministerio de Educación, Ciencia e Innovación (http://www.mecd.gob.es/portada-mecd/) and OAPN 762/2012, Ministerio de Agricultura, Alimentación y Medio Ambiente (http://www.magrama.gob.es/es/)