Abstract
Genetic association studies suggest that variations in the 5-hydroxytryptamine (5-HT; serotonin) transporter (5-HTT) gene are associated with susceptibility to psychiatric disorders such as anxiety or posttraumatic stress disorder. Individuals carrying high 5-HTT-expressing gene variants display low amygdala reactivity to fearful stimuli. Mice overexpressing the 5-HTT (5-HTTOE), an animal model of this human variation, show impaired fear, together with reduced fear-evoked theta oscillations in the basolateral amygdala (BLA). However, it is unclear how variation in 5-HTT gene expression impacts on the microcircuitry of the BLA to change behavior. We addressed this issue by investigating the activity of parvalbumin (PV)-expressing interneurons (PVINs), the biggest IN population in the basal amygdala (BA). We found that increased 5-HTT expression impairs the recruitment of PVINs (measured by their c-Fos immunoreactivity) during fear. Ex vivo patch-clamp recordings demonstrated that the depolarizing effect of 5-HT on PVINs was mediated by 5-HT2A receptor. In 5-HTTOE mice, 5-HT-evoked depolarization of PVINs and synaptic inhibition of principal cells, which provide the major output of the BA, were impaired. This deficit was because of reduced 5-HT2A function and not because of increased 5-HT uptake. Collectively, these findings provide novel cellular mechanisms that are likely to contribute to differences in emotional behaviors linked with genetic variations of the 5-HTT.
Similar content being viewed by others
Log in or create a free account to read this content
Gain free access to this article, as well as selected content from this journal and more on nature.com
or
References
Araneda R, Andrade R (1991). 5-Hydroxytryptamine2 and 5-hydroxytryptamine 1A receptors mediate opposing responses on membrane excitability in rat association cortex. Neuroscience 40: 399–412.
Asan E, Steinke M, Lesch K (2013). Serotonergic innervation of the amygdala: targets, receptors, and implications for stress and anxiety. Histochem Cell Biol 139: 785–813.
Ballenger JC (1999). Current treatments of the anxiety disorders in adults. Biol Psychiatry 46: 1579–1594.
Barkus C, Line SJ, Huber A, Capitao L, Lima J, Jennings K et al (2014). Variation in serotonin transporter expression modulates fear-evoked hemodynamic responses and theta-frequency neuronal oscillations in the amygdala. Biol Psychiatry 75: 901–908.
Béïque J-C, Campbell B, Perring P, Hamblin MW, Walker P, Mladenovic L et al (2004). Serotonergic regulation of membrane potential in developing rat prefrontal cortex: coordinated expression of 5-hydroxytryptamine (5-HT)1A, 5-HT2A, and 5-HT7 receptors. J Neurosci 24: 4807–4817.
Bienvenu TCM, Busti D, Magill PJ, Ferraguti F, Capogna M (2012). Cell-type-specific recruitment of amygdala interneurons to hippocampal theta rhythm and noxious stimuli in vivo. Neuron 74: 1059–1074.
Blakely RD, De Felice LJ, Hartzell HC (1994). Molecular physiology of norepinephrine and serotonin transporters. J Exp Biol 196: 263–281.
Bonn M, Schmitt A (2013). Serotonergic innervation and serotonin receptor expression of NPY-producing neurons in the rat lateral and basolateral amygdaloid nuclei. Brain Struct 218: 421–435.
Buzsáki G (2002). Theta oscillations in the hippocampus. Neuron 33: 325–340.
Canli T, Omura K, Haas BW, Fallgatter A, Constable RT, Lesch KP (2005). Beyond affect: a role for genetic variation of the serotonin transporter in neural activation during a cognitive attention task. Proc Natl Acad Sci USA 102: 12224–12229.
Caspi A, Sugden K, Moffitt TE, Taylor A, Craig IW, Harrington H et al (2003). Influence of life stress on depression: moderation by a polymorphism in the 5-HTT gene. Science 301: 386–389.
Courtin J, Chaudun F, Rozeske RR, Karalis N, Gonzalez-Campo C, Wurtz H et al (2014). Prefrontal parvalbumin interneurons shape neuronal activity to drive fear expression. Nature 505: 92–96.
Gross C, Zhuang X, Stark K, Ramboz S, Oosting R, Kirby L et al (2002). Serotonin1A receptor acts during development to establish normal anxiety-like behaviour in the adult. Nature 416: 396–400.
Hariri AR, Mattay VS, Tessitore A, Kolachana B, Fera F, Goldman D et al (2002). Serotonin transporter genetic variation and the response of the human amygdala. Science 297: 400–403.
Hensler JG (2006). Serotonergic modulation of the limbic system. Neurosci Biobehav Rev 30: 203–214.
Holmes A, Lit Q, Murphy DL, Gold E, Crawley JN (2003). Abnormal anxiety-related behavior in serotonin transporter null mutant mice: the influence of genetic background. Genes Brain Behav 2: 365–380.
Hu X-Z, Lipsky RH, Zhu G, Akhtar LA, Taubman J, Greenberg BD et al (2006). Serotonin transporter promoter gain-of-function genotypes are linked to obsessive-compulsive disorder. Am J Hum Genet 78: 815–826.
Jackson J, Dickson CT, Bland BH (2008). Median raphe stimulation disrupts hippocampal theta via rapid inhibition and state-dependent phase reset of theta-related neural circuitry. J Neurophysiol 99: 3009–3026.
Jennings KA, Loder MK, Sheward WJ, Pei Q, Deacon RMJ, Benson MA et al (2006). Increased expression of the 5-HT transporter confers a low-anxiety phenotype linked to decreased 5-HT transmission. J Neurosci 26: 8955–8964.
Jennings KA, Sheward WJ, Harmar AJ, Sharp T (2008). Evidence that genetic variation in 5-HT transporter expression is linked to changes in 5-HT2A receptor function. Neuropharmacology 54: 776–783.
Jiang X, Xing G, Yang C, Verma A, Zhang L, Li H (2009). Stress impairs 5-HT2A receptor-mediated serotonergic facilitation of GABA release in juvenile rat basolateral amygdala. Neuropsychopharmacology 34: 410–423.
Klausberger T, Magill PJ, Márton LF, Roberts JDB, Cobden PM, Buzsáki G et al (2003). Brain-state- and cell-type-specific firing of hippocampal interneurons in vivo. Nature 421: 844–848.
Kocsis B, Vertes RP (1992). Dorsal raphe neurons: synchronous discharge with the theta rhythm of the hippocampus in the freely behaving rat. J Neurophysiol 68: 1463–1467.
Lee H-J, Lee M-S, Kang R-H, Kim H, Kim S-D, Kee B-S et al (2005). Influence of the serotonin transporter promoter gene polymorphism on susceptibility to posttraumatic stress disorder. Depress Anxiety 21: 135–139.
Lesch KP, Bengel D, Heils A, Sabol SZ, Greenberg BD, Petri S et al (1996). Association of anxiety-related traits with a polymorphism in the serotonin transporter gene regulatory region. Science 274: 1527–1531.
Li Q, Wichems CH, Ma L, Van de Kar LD, Garcia F, Murphy DL (2003). Brain region-specific alterations of 5-HT2A and 5-HT2C receptors in serotonin transporter knockout mice. J Neurochem 84: 1256–1265.
Line SJ, Barkus C, Rawlings N, Jennings K, McHugh S, Sharp T et al (2014). Reduced sensitivity to both positive and negative reinforcement in mice over-expressing the 5-hydroxytryptamine transporter. Eur J Neurosci 40: 3735–3745.
Lundberg J, Borg J, Halldin C, Farde L (2007). A PET study on regional coexpression of 5-HT1A receptors and 5-HTT in the human brain. Psychopharmacology (Berl) 195: 425–433.
Manko M, Bienvenu TCM, Dalezios Y, Capogna M (2012). Neurogliaform cells of amygdala: a source of slow phasic inhibition in the basolateral complex. J Physiol 590: 5611–5627.
Marek GJ, Martin-Ruiz R, Abo A, Artigas F (2005). The selective 5-HT2A receptor antagonist M100907 enhances antidepressant-like behavioral effects of the SSRI fluoxetine. Neuropsychopharmacology 30: 2205–2215.
Mascagni F, McDonald AJ (2007). A novel subpopulation of 5-HT type 3A receptor subunit immunoreactive interneurons in the rat basolateral amygdala. Neuroscience 144: 1015–1024.
McDonald AJ, Mascagni F (2001). Colocalization of calcium-binding proteins and GABA in neurons of the rat basolateral amygdala. Neuroscience 105: 681–693.
McDonald AJ, Mascagni F (2007). Neuronal localization of 5-HT type 2A receptor immunoreactivity in the rat basolateral amygdala. Neuroscience 146: 306–320.
Murphy SE, Norbury R, Godlewska BR, Cowen PJ, Mannie ZM, Harmer CJ et al (2013). The effect of the serotonin transporter polymorphism (5-HTTLPR) on amygdala function: a meta-analysis. Mol Psychiatry 18: 512–520.
Narayanan V, Heiming RS, Jansen F, Lesting J, Sachser N, Pape H-C et al (2011). Social defeat: impact on fear extinction and amygdala-prefrontal cortical theta synchrony in 5-HTT deficient mice. PLoS One 6: e22600.
Pezawas L, Meyer-Lindenberg A, Drabant EM, Verchinski B a, Munoz KE, Kolachana BS et al (2005). 5-HTTLPR polymorphism impacts human cingulate-amygdala interactions: a genetic susceptibility mechanism for depression. Nat Neurosci 8: 828–834.
Popescu AT, Paré D (2011). Synaptic interactions underlying synchronized inhibition in the basal amygdala: evidence for existence of two types of projection cells. J Neurophysiol 105: 687–696.
Rainnie DG (1999). Serotonergic modulation of neurotransmission in the rat basolateral amygdala. J Neurophysiol 82: 69–85.
Richmond MA, Murphy CA, Pouzet B, Schmid P, Rawlins JNP, Feldon J (1998). A computer controlled analysis of freezing behaviour. J Neurosci Methods 86: 91–99.
Ryan SJ, Ehrlich DE, Jasnow AM, Daftary S, Madsen TE, Rainnie DG (2012). Spike-timing precision and neuronal synchrony are enhanced by an interaction between synaptic inhibition and membrane oscillations in the amygdala. PLoS One 7: e35320.
Sarkar A, Chachra P, Vaidya VA (2013). Postnatal fluoxetine-evoked anxiety is prevented by concomitant 5-HT2A/C receptor blockade and mimicked by postnatal 5-HT2A/C receptor stimulation. Biol Psychiatry 76: 858–868.
Sosulina L, Meis S, Seifert G, Steinhäuser C, Pape H-C (2006). Classification of projection neurons and interneurons in the rat lateral amygdala based upon cluster analysis. Mol Cell Neurosci 33: 57–67.
Spannuth BM, Hale MW, Evans AK, Lukkes JL, Campeau S, Lowry CA (2011). Investigation of a central nucleus of the amygdala/dorsal raphe nucleus serotonergic circuit implicated in fear-potentiated startle. Neuroscience 179: 104–119.
Uher R, McGuffin P (2010). The moderation by the serotonin transporter gene of environmental adversity in the etiology of depression: 2009 update. Mol Psychiatry 15: 18–22.
Wellman CL, Izquierdo A, Garrett JE, Martin KP, Carroll J, Millstein R et al (2007). Impaired stress-coping and fear extinction and abnormal corticolimbic morphology in serotonin transporter knock-out mice. J Neurosci 27: 684–691.
Wolff SBE, Gründemann J, Tovote P, Krabbe S, Jacobson G a, Müller C et al (2014). Amygdala interneuron subtypes control fear learning through disinhibition. Nature 509: 453–458.
Woodruff AR, Sah P (2007). Inhibition and synchronization of basal amygdala principal neuron spiking by parvalbumin-positive interneurons. J Neurophysiol 98: 2956–2961.
Zanoveli JM, Carvalho MC, Cunha JM, Brandão ML (2009). Extracellular serotonin level in the basolateral nucleus of the amygdala and dorsal periaqueductal gray under unconditioned and conditioned fear states: an in vivo microdialysis study. Brain Res 1294: 106–115.
Acknowledgements
We thank K Whitworth, L Norman, J Janson, B Micklem, and L Black for excellent technical support.
Author information
Authors and Affiliations
Corresponding author
Additional information
Supplementary Information accompanies the paper on the Neuropsychopharmacology website
Supplementary information
Rights and permissions
About this article
Cite this article
Bocchio, M., Fucsina, G., Oikonomidis, L. et al. Increased Serotonin Transporter Expression Reduces Fear and Recruitment of Parvalbumin Interneurons of the Amygdala. Neuropsychopharmacol 40, 3015–3026 (2015). https://doi.org/10.1038/npp.2015.157
Received:
Revised:
Accepted:
Published:
Issue date:
DOI: https://doi.org/10.1038/npp.2015.157
This article is cited by
-
Distinct serotonergic pathways to the amygdala underlie separate behavioral features of anxiety
Nature Neuroscience (2022)
-
Enhanced discriminative aversive learning and amygdala responsivity in 5-HT transporter mutant mice
Translational Psychiatry (2019)
-
Inhibition in the amygdala anxiety circuitry
Experimental & Molecular Medicine (2018)
-
Inhibition of serotonin transporters disrupts the enhancement of fear memory extinction by 3,4-methylenedioxymethamphetamine (MDMA)
Psychopharmacology (2017)
