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Williams IR, Ryugo DK. Bilateral and symmetric glycinergic and glutamatergic projections from the LSO to the IC in the CBA/CaH mouse. Front Neural Circuits 2024; 18:1430598. [PMID: 39184455 PMCID: PMC11341401 DOI: 10.3389/fncir.2024.1430598] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2024] [Accepted: 07/10/2024] [Indexed: 08/27/2024] Open
Abstract
Auditory space has been conceptualized as a matrix of systematically arranged combinations of binaural disparity cues that arise in the superior olivary complex (SOC). The computational code for interaural time and intensity differences utilizes excitatory and inhibitory projections that converge in the inferior colliculus (IC). The challenge is to determine the neural circuits underlying this convergence and to model how the binaural cues encode location. It has been shown that midbrain neurons are largely excited by sound from the contralateral ear and inhibited by sound leading at the ipsilateral ear. In this context, ascending projections from the lateral superior olive (LSO) to the IC have been reported to be ipsilaterally glycinergic and contralaterally glutamatergic. This study used CBA/CaH mice (3-6 months old) and applied unilateral retrograde tracing techniques into the IC in conjunction with immunocytochemical methods with glycine and glutamate transporters (GlyT2 and vGLUT2, respectively) to analyze the projection patterns from the LSO to the IC. Glycinergic and glutamatergic neurons were spatially intermixed within the LSO, and both types projected to the IC. For GlyT2 and vGLUT2 neurons, the average percentage of ipsilaterally and contralaterally projecting cells was similar (ANOVA, p = 0.48). A roughly equal number of GlyT2 and vGLUT2 neurons did not project to the IC. The somatic size and shape of these neurons match the descriptions of LSO principal cells. A minor but distinct population of small (< 40 μm2) neurons that labeled for GlyT2 did not project to the IC; these cells emerge as candidates for inhibitory local circuit neurons. Our findings indicate a symmetric and bilateral projection of glycine and glutamate neurons from the LSO to the IC. The differences between our results and those from previous studies suggest that species and habitat differences have a significant role in mechanisms of binaural processing and highlight the importance of research methods and comparative neuroscience. These data will be important for modeling how excitatory and inhibitory systems converge to create auditory space in the CBA/CaH mouse.
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Affiliation(s)
- Isabella R. Williams
- Garvan Institute of Medical Research, Darlinghurst, NSW, Australia
- School of Medical Sciences, University of New South Wales, Kensington, NSW, Australia
| | - David K. Ryugo
- Garvan Institute of Medical Research, Darlinghurst, NSW, Australia
- School of Medical Sciences, University of New South Wales, Kensington, NSW, Australia
- Department of Otolaryngology, Head, Neck and Skull Base Surgery, St. Vincent’s Hospital, Darlinghurst, NSW, Australia
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Saré RM, Lemons A, Smith CB. Behavior Testing in Rodents: Highlighting Potential Confounds Affecting Variability and Reproducibility. Brain Sci 2021; 11:brainsci11040522. [PMID: 33924037 PMCID: PMC8073298 DOI: 10.3390/brainsci11040522] [Citation(s) in RCA: 46] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2021] [Revised: 04/05/2021] [Accepted: 04/08/2021] [Indexed: 12/17/2022] Open
Abstract
Rodent models of brain disorders including neurodevelopmental, neuropsychiatric, and neurodegenerative diseases are essential for increasing our understanding of underlying pathology and for preclinical testing of potential treatments. Some of the most important outcome measures in such studies are behavioral. Unfortunately, reports from different labs are often conflicting, and preclinical studies in rodent models are not often corroborated in human trials. There are many well-established tests for assessing various behavioral readouts, but subtle aspects can influence measurements. Features such as housing conditions, conditions of testing, and the sex and strain of the animals can all have effects on tests of behavior. In the conduct of behavior testing, it is important to keep these features in mind to ensure the reliability and reproducibility of results. In this review, we highlight factors that we and others have encountered that can influence behavioral measures. Our goal is to increase awareness of factors that can affect behavior in rodents and to emphasize the need for detailed reporting of methods.
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Kolter JF, Hildenbrand MF, Popp S, Nauroth S, Bankmann J, Rother L, Waider J, Deckert J, Asan E, Jakob PM, Lesch KP, Schmitt-Böhrer A. Serotonin transporter genotype modulates resting state and predator stress-induced amygdala perfusion in mice in a sex-dependent manner. PLoS One 2021; 16:e0247311. [PMID: 33606835 PMCID: PMC7895400 DOI: 10.1371/journal.pone.0247311] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2020] [Accepted: 02/04/2021] [Indexed: 12/16/2022] Open
Abstract
The serotonin transporter (5-HTT) is a key molecule of serotoninergic neurotransmission and target of many anxiolytics and antidepressants. In humans, 5-HTT gene variants resulting in lower expression levels are associated with behavioral traits of anxiety. Furthermore, functional magnetic resonance imaging (fMRI) studies reported increased cerebral blood flow (CBF) during resting state (RS) and amygdala hyperreactivity. 5-HTT deficient mice as an established animal model for anxiety disorders seem to be well suited for investigating amygdala (re-)activity in an fMRI study. We investigated wildtype (5-HTT+/+), heterozygous (5-HTT+/-), and homozygous 5-HTT-knockout mice (5-HTT-/-) of both sexes in an ultra-high-field 17.6 Tesla magnetic resonance scanner. CBF was measured with continuous arterial spin labeling during RS, stimulation state (SS; with odor of rats as aversive stimulus), and post-stimulation state (PS). Subsequently, post mortem c-Fos immunohistochemistry elucidated neural activation on cellular level. The results showed that in reaction to the aversive odor CBF in total brain and amygdala of all mice significantly increased. In male 5-HTT+/+ mice amygdala RS CBF levels were found to be significantly lower than in 5-HTT+/- mice. From RS to SS 5-HTT+/+ amygdala perfusion significantly increased compared to both 5-HTT+/- and 5-HTT-/- mice. Perfusion level changes of male mice correlated with the density of c-Fos-immunoreactive cells in the amygdaloid nuclei. In female mice the perfusion was not modulated by the 5-Htt-genotype, but by estrous cycle stages. We conclude that amygdala reactivity is modulated by the 5-Htt genotype in males. In females, gonadal hormones have an impact which might have obscured genotype effects. Furthermore, our results demonstrate experimental support for the tonic model of 5-HTTLPR function.
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Affiliation(s)
- Jann F. Kolter
- Department of Psychiatry, Psychosomatics and Psychotherapy, Center of Mental Health, University of Wuerzburg, Wuerzburg, Germany
- Division of Molecular Psychiatry, Department of Psychiatry, Psychosomatics and Psychotherapy, Center of Mental Health, University of Wuerzburg, Wuerzburg, Germany
| | - Markus F. Hildenbrand
- Department of Magnetic Resonance and X-Ray Imaging, Fraunhofer Development Center X-Ray Technology, Wuerzburg, Germany
| | - Sandy Popp
- Division of Molecular Psychiatry, Department of Psychiatry, Psychosomatics and Psychotherapy, Center of Mental Health, University of Wuerzburg, Wuerzburg, Germany
| | - Stephan Nauroth
- Division of Molecular Psychiatry, Department of Psychiatry, Psychosomatics and Psychotherapy, Center of Mental Health, University of Wuerzburg, Wuerzburg, Germany
| | - Julian Bankmann
- Department of Psychiatry, Psychosomatics and Psychotherapy, Center of Mental Health, University of Wuerzburg, Wuerzburg, Germany
| | - Lisa Rother
- Department of Psychiatry, Psychosomatics and Psychotherapy, Center of Mental Health, University of Wuerzburg, Wuerzburg, Germany
| | - Jonas Waider
- Division of Molecular Psychiatry, Department of Psychiatry, Psychosomatics and Psychotherapy, Center of Mental Health, University of Wuerzburg, Wuerzburg, Germany
| | - Jürgen Deckert
- Department of Psychiatry, Psychosomatics and Psychotherapy, Center of Mental Health, University of Wuerzburg, Wuerzburg, Germany
| | - Esther Asan
- Institute of Anatomy and Cell Biology, University of Wuerzburg, Wuerzburg, Germany
| | - Peter M. Jakob
- Department of Experimental Physics 5, University of Wuerzburg, Wuerzburg, Germany
| | - Klaus-Peter Lesch
- Division of Molecular Psychiatry, Department of Psychiatry, Psychosomatics and Psychotherapy, Center of Mental Health, University of Wuerzburg, Wuerzburg, Germany
| | - Angelika Schmitt-Böhrer
- Department of Psychiatry, Psychosomatics and Psychotherapy, Center of Mental Health, University of Wuerzburg, Wuerzburg, Germany
- * E-mail:
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Whittaker AL, Hickman DL. The Impact of Social and Behavioral Factors on Reproducibility in Terrestrial Vertebrate Models. ILAR J 2020; 60:252-269. [PMID: 32720675 DOI: 10.1093/ilar/ilaa005] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2019] [Revised: 01/30/2020] [Accepted: 02/07/2020] [Indexed: 12/12/2022] Open
Abstract
The use of animal models remains critical in preclinical and translational research. The reliability of the animal models and aspects of their validity is likely key to effective translation of findings to medicine. However, despite considerable uniformity in animal models brought about by control of genetics, there remain a number of social as well as innate and acquired behavioral characteristics of laboratory animals that may impact on research outcomes. These include the effects of strain and genetics, age and development, sex, personality and affective states, and social factors largely brought about by housing and husbandry. In addition, aspects of the testing environment may also influence research findings. A number of considerations resulting from the animals' innate and acquired behavioral characteristics as well as their social structures are described. Suggestions for minimizing the impact of these factors on research are provided.
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Affiliation(s)
- Alexandra L Whittaker
- School of Animal and Veterinary Sciences, University of Adelaide, Roseworthy Campus, South Australia, Australia
| | - Debra L Hickman
- Laboratory Animal Resource Center, Indiana University, Indianapolis, Indiana
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Exposure to Chemical Cues from Predator-Exposed Conspecifics Increases Reproduction in a Wild Rodent. Sci Rep 2018; 8:17214. [PMID: 30464245 PMCID: PMC6249244 DOI: 10.1038/s41598-018-35568-0] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2018] [Accepted: 11/01/2018] [Indexed: 11/10/2022] Open
Abstract
Predation involves more than just predators consuming prey. Indirect effects, such as fear responses caused by predator presence, can have consequences for prey life history. Laboratory experiments have shown that some rodents can recognize fear in conspecifics via alarm pheromones. Individuals exposed to alarm pheromones can exhibit behavioural alterations that are similar to those displayed by predator-exposed individuals. Yet the ecological and evolutionary significance of alarm pheromones in wild mammals remains unclear. We investigated how alarm pheromones affect the behaviour and fitness of wild bank voles (Myodes glareolus) in outdoor enclosures. Specifically, we compared the effects of exposure of voles living in a natural environment to a second-hand fear cue, bedding material used by predator-exposed voles. Control animals were exposed to bedding used by voles with no predator experience. We found a ca. 50% increase in litter size in the group exposed to the predator cue. Furthermore, female voles were attracted to and males were repelled by trap-associated bedding that had been used by predator-exposed voles. Movement and foraging were not significantly affected by the treatment. Our results suggest that predation risk can exert population-level effects through alarm pheromones on prey individuals that did not encounter a direct predator cue.
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Quantitative inheritance of volatile pheromones and darcin and their interaction in olfactory preferences of female mice. Sci Rep 2017; 7:2094. [PMID: 28522864 PMCID: PMC5437034 DOI: 10.1038/s41598-017-02259-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2016] [Accepted: 04/24/2017] [Indexed: 11/10/2022] Open
Abstract
In this study, we examined how urine-borne volatile compounds (UVCs) and darcin of male mice are inherited from parents and interact to modulate the olfactory preferences of females using two inbred strains of mice, C57Bl/6 (C57) and BALB/c (BALB), and their reciprocal hybrids (BC = BALB♀× C57♂; CB = C57♀ × BALB♂). Chemical analysis revealed that the UVCs of C57BL/6 males were quantitatively distinguishable from those of BALB/c males. Darcin was detected in C57 urine, but not in BALB urine. The levels of UVCs and darcin in both BC and CB were intermediate between those of C57 and BALB. Behaviourally, C57 females consistently preferred BALB male urine over C57 or CB males despite that there are trace amounts of darcin in BALB urine. However, the preference for BALB urine disappeared in contact two-choice tests of BALB vs. BC pairs, and restored when recombinant darcin was added to BALB male urine. Our results suggested that both UVCs and darcin in male mice are quantitatively inherited and interact to affect the olfactory preferences of females.
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