Adult microbiota‐deficient mice have distinct dendritic morphological changes: differential effects in the amygdala and hippocampus. (8th July 2016)

• Record Type: Journal Article
• Authors: Luczynski, Pauline; Whelan, Seán O.; O'Sullivan, Colette; Clarke, Gerard; Shanahan, Fergus; Dinan, Timothy G.; Cryan, John F.
• Editors: Gaspar, Patricia
• Is Part Of: European journal of neuroscience. Volume 44:Number 9(2016:Nov.)
• Page Start: 2654
• Page End: 2666
• Publication Date: 2016-07-08
• Subjects: brain volume -- dendritic spines -- design‐based stereology -- germ‐free mouse -- microbiota–gut–brain axis; Nervous system -- Periodicals; 612.8
• DOI: 10.1111/ejn.13291
• Languages: English
• ISSNs: 0953-816X

Abstract

Abstract: Increasing evidence implicates the microbiota in the regulation of brain and behaviour. Germ‐free mice (GF; microbiota deficient from birth) exhibit altered stress hormone signalling and anxiety‐like behaviours as well as deficits in social cognition. Although the mechanisms underlying the ability of the gut microbiota to influence stress responsivity and behaviour remain unknown, many lines of evidence point to the amygdala and hippocampus as likely targets. Thus, the aim of this study was to determine if the volume and dendritic morphology of the amygdala and hippocampus differ in GF versus conventionally colonized (CC) mice. Volumetric estimates revealed significant amygdalar and hippocampal expansion in GF compared to CC mice. We also studied the effect of GF status on the level of single neurons in the basolateral amygdala (BLA) and ventral hippocampus. In the BLA, the aspiny interneurons and pyramidal neurons of GF mice exhibited dendritic hypertrophy. The BLA pyramidal neurons of GF mice had more thin, stubby and mushroom spines. In contrast, the ventral hippocampal pyramidal neurons of GF mice were shorter, less branched and had less stubby and mushroom spines. When compared to controls, dentate granule cells of GF mice were less branched but did not differ in spine density. These findings suggest that the microbiota is required for the normal gross morphology and ultrastructure of the amygdala and hippocampus and that this neural remodelling may contribute to the maladaptive stress responsivity and behavioural profile observed in GF mice. Abstract : Germ‐free mice (GF; microbiota deficient from birth) exhibit alterations in stress responsivity, anxiety‐like behaviour, and sociability, effects influenced by the amygdala and hippocampus. Here, we show that there are alterations in the gross morphology and ultrastructure of the amygdala and hippocampus of GF mice. These findings indicate that the microbiota is required for normal brain structure and that these neuronal changes may contribute to the maladaptive behavioural profile of GF mice.