Genetically driven brain serotonin deficiency facilitates panic-like escape behavior in mice

Multiple lines of evidence implicate brain serotonin (5-hydroxytryptamine; 5-HT) system dysfunction in the pathophysiology of stressor-related and anxiety disorders. Here we investigate the influence of constitutively deficient 5-HT synthesis on stressor-related anxiety-like behaviors using Tryptoph...

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Bibliographic Details
Published in:	Translational psychiatry Vol. 7; no. 10; p. e1246
Main Authors:	Waider, J, Popp, S, Lange, M D, Kern, R, Kolter, J F, Kobler, J, Donner, N C, Lowe, K R, Malzbender, J H, Brazell, C J, Arnold, M R, Aboagye, B, Schmitt-Böhrer, A, Lowry, C A, Pape, H C, Lesch, K P
Format:	Journal Article
Language:	English
Published:	London Nature Publishing Group UK 03-10-2017 Nature Publishing Group
Subjects:	631/378/1595 64 64/60 692/53 82 82/51 Agoraphobia - physiopathology Amygdala - metabolism Amygdala - physiopathology Animals Anxiety Anxiety - physiopathology Behavioral Sciences Biological Psychology Electroshock Escape Reaction Fear gamma-Aminobutyric Acid - metabolism Inhibitory Postsynaptic Potentials Male Medicine Medicine & Public Health Mice, Knockout Neurosciences Original original-article Panic Disorder - physiopathology Pharmacotherapy Psychiatry Raphe Nuclei - metabolism Rodents Serotonin - deficiency Serotonin - physiology Serotonin Plasma Membrane Transport Proteins - metabolism Tryptophan Hydroxylase - genetics
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Summary:	Multiple lines of evidence implicate brain serotonin (5-hydroxytryptamine; 5-HT) system dysfunction in the pathophysiology of stressor-related and anxiety disorders. Here we investigate the influence of constitutively deficient 5-HT synthesis on stressor-related anxiety-like behaviors using Tryptophan hydroxylase 2 ( Tph2 ) mutant mice. Functional assessment of c-Fos after associated foot shock, electrophysiological recordings of GABAergic synaptic transmission, differential expression of the Slc6a4 gene in serotonergic neurons were combined with locomotor and anxiety-like measurements in different contextual settings. Our findings indicate that constitutive Tph2 inactivation and consequential lack of 5-HT synthesis in Tph2 null mutant mice ( Tph2 −/− ) results in increased freezing to associated foot shock and a differential c-Fos activity pattern in the basolateral complex of the amygdala. This is accompanied by altered GABAergic transmission as observed by recordings of inhibitory postsynaptic currents on principal neurons in the basolateral nucleus, which may explain increased fear associated with hyperlocomotion and escape-like responses in aversive inescapable contexts. In contrast, lifelong 5-HT deficiency as observed in Tph2 heterozygous mice ( Tph +/ − ) is able to be compensated through reduced GABAergic transmission in the basolateral nucleus of the amygdala based on Slc6a4 mRNA upregulation in subdivisions of dorsal raphe neurons. This results in increased activity of the basolateral nucleus of the amygdala due to associated foot shock. In conclusion, our results reflect characteristic syndromal dimensions of panic disorder and agoraphobia. Thus, constitutive lack of 5-HT synthesis influence the risk for anxiety- and stressor-related disorders including panic disorder and comorbid agoraphobia through the absence of GABAergic-dependent compensatory mechanisms in the basolateral nucleus of the amygdala.
Bibliography:	ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 These authors contributed equally to this work.
ISSN:	2158-3188 2158-3188
DOI:	10.1038/tp.2017.209