常常玩土未必是件壞事,。根據(jù)發(fā)表在近期《神經(jīng)科學(xué)》（Neuroscience）雜志上的一項研究，一種土壤中的常見細(xì)菌能夠激活大腦中的神經(jīng)元,，從而制造出一種負(fù)責(zé)調(diào)控情緒的化學(xué)物質(zhì)——血清素(serotonin,，也稱色胺)。
通常認(rèn)為,，缺乏血清素會使人精神抑郁消沉,，而最新研究結(jié)果將加深人們對免疫系統(tǒng)失衡導(dǎo)致一些人情緒低落的科學(xué)認(rèn)識。進(jìn)行該研究的是英國布里斯托爾大學(xué)（University of Bristol）和倫敦大學(xué)學(xué)院（University College London,，簡稱UCL）的科學(xué)家,，他們對該研究的興趣源于偶然?？茖W(xué)家意外發(fā)現(xiàn),，利用母牛分枝桿菌（Mycobacterium vaccae）對一些癌癥病人進(jìn)行治療后，他們的生活質(zhì)量有所增加,。論文第一作者,、布里斯托爾大學(xué)Chris Lowry博士和同事認(rèn)為，造成這一結(jié)果的原因可能是產(chǎn)生血清素的大腦神經(jīng)元被激活,。
利用小鼠進(jìn)行的研究證實了這一猜測,。Lowry和同事發(fā)現(xiàn)，母牛分枝桿菌能夠激活小鼠大腦中一組制造血清素的神經(jīng)元,，從而改善小鼠的情緒和行為活動,。
Lowry表示，該研究有助于人們理解身體和大腦的溝通機制,，以及良好的免疫系統(tǒng)對維持精神健康的重要性,。
部分英文原文：
Identification of an immune-responsive mesolimbocortical serotonergic system: Potential role in regulation of emotional behavior
C.A. Lowrya, , , J.H. Hollisa, 1, A. de Vriesa, 1, B. Pana, L.R. Brunetb, J.R.F. Huntb, J.F.R. Patonc, E. van Kampena, D.M. Knighta, A.K. Evansa, G.A.W. Rookb and S.L. Lightmana
aHenry Wellcome Laboratories for Integrative Neuroscience and Endocrinology, University of Bristol, Dorothy Hodgkin Building, Bristol BS1 3NY, UK
bCentre for Infectious Diseases and International Health, Windeyer Institute of Medical Sciences, University College London, W1T 4JF, UK
cDepartment of Physiology, Bristol Heart Institute, University of Bristol, School of Medical Sciences, Bristol, BS8 1TD, UK
Accepted 30 January 2007. Available online 28 March 2007.
Abstract
Peripheral immune activation can have profound physiological and behavioral effects including induction of fever and sickness behavior. One mechanism through which immune activation or immunomodulation may affect physiology and behavior is via actions on brainstem neuromodulatory systems, such as serotonergic systems. We have found that peripheral immune activation with antigens derived from the nonpathogenic, saprophytic bacterium, Mycobacterium vaccae, activated a specific subset of serotonergic neurons in the interfascicular part of the dorsal raphe nucleus (DRI) of mice, as measured by quantification of c-Fos expression following intratracheal (12 h) or s.c. (6 h) administration of heat-killed, ultrasonically disrupted M. vaccae, or heat-killed, intact M. vaccae, respectively. These effects were apparent after immune activation by M. vaccae or its components but not by ovalbumin, which induces a qualitatively different immune response. The effects of immune activation were associated with increases in serotonin metabolism within the ventromedial prefrontal cortex, consistent with an effect of immune activation on mesolimbocortical serotonergic systems. The effects of M. vaccae administration on serotonergic systems were temporally associated with reductions in immobility in the forced swim test, consistent with the hypothesis that the stimulation of mesolimbocortical serotonergic systems by peripheral immune activation alters stress-related emotional behavior. These findings suggest that the immune-responsive subpopulation of serotonergic neurons in the DRI is likely to play an important role in the neural mechanisms underlying regulation of the physiological and pathophysiological responses to both acute and chronic immune activation, including regulation of mood during health and disease states. Together with previous studies, these findings also raise the possibility that immune stimulation activates a functionally and anatomically distinct subset of serotonergic neurons, different from the subset of serotonergic neurons activated by anxiogenic stimuli or uncontrollable stressors. Consequently, selective activation of specific subsets of serotonergic neurons may have distinct behavioral outcomes.
Key words: depression; hippocampus; prefrontal cortex; raphe; 5-HT; vagus
Abbreviations: ANOVA, analysis of variance; AP, area postrema; c-Fos-ir, c-Fos-like-immunoreactive; DR, dorsal raphe nucleus;DRC, dorsal raphe nucleus, caudal part; DRI, dorsal raphe nucleus, interfascicular part; ECG, electrocardiogram; EDTA, ethylenediaminetetraacetic acid; EMG, electromyogram; HPLC, high pressure liquid chromatography; IL-6, interleukin-6; IL-10, interleukin-10; i.t., intratracheal; LPS, lipopolysaccharide; LSD, least significant difference; mlf, medial longitudinal fasciculus; M. vaccae, Mycobacterium vaccae; Mv-NC, Mycobacterium vaccae antigen, M. vaccae coupled to nitrocellulose beads; NC, nitrocellulose beads; nTS, nucleus of the solitary tract; OVA, ovalbumin; OVA-NC, ovalbumin coupled to nitrocellulose beads; PBG, phenylbiguanide; PBS, phosphate-buffered saline; PBST, phosphate-buffered saline containing 0.3% Triton X-100; RMg, raphe magnus; ROb, raphe obscurus; S.E.M., standard error of the mean; SolDL, dorsolateral part of the nucleus of the solitary tract; TGF-β, transforming growth factor-β; Th1, T helper cell 1; Th2, T helper cell 2; TNF-α, tumor necrosis factor-α; Treg, T regulatory cell; 5-HIAA, 5-hydroxyindoleacetic acid; 5-HT, serotonin
Corresponding author. Tel: +44-117-331-3119; fax: +44-117-331-3120.
1 These authors contributed equally to this work.
