Anatomical Coupling of Locomotor and Auditory Neurons in Desert Kangaroo Rats
Additional Funding Sources
The project described was supported by a student grant from the UI Office of Undergraduate Research.
Abstract
Acoustic stimuli-induced startle response in mammals may be modulated by vigilance and an elevated arousal state to allow for a more rapid acoustic stimulus-induced response in locomotor systems. Though this phenomenon is found in many mammals, the nature of anatomical connectivity between auditory and locomotor neurons remains unclear in desert kangaroo rats. Identifying the neuroanatomical nature of this auditory-locomotor pathway is a major step towards understanding how species-specific anatomical and functional properties of this pathway may underpin success rate of kangaroo rats in the wild. To evaluate the anatomical connectivity, a trans-synaptic retrograde pseudorabies virus was injected into the right gastrocnemius muscle and induces the expression of green fluorescent protein in all presynaptic neurons that are synaptically connected to the afferent motor neuron of the muscle, whether they be motor or not. Following 5-7 days of recovery after viral injection, kangaroo rats were euthanized, and their brains removed, frozen and sectioned coronally. Tissue sections containing all central auditory nuclei were then mounted directly onto slides or immunohistochemically labeled to amplify visibility of GFP expression. Sections were imaged through a microscope where GFP expression was observed in motor nuclei within the brainstem and midbrain along with the cochlear nucleus, a key site for mediating the acoustic startle response.
Anatomical Coupling of Locomotor and Auditory Neurons in Desert Kangaroo Rats
Acoustic stimuli-induced startle response in mammals may be modulated by vigilance and an elevated arousal state to allow for a more rapid acoustic stimulus-induced response in locomotor systems. Though this phenomenon is found in many mammals, the nature of anatomical connectivity between auditory and locomotor neurons remains unclear in desert kangaroo rats. Identifying the neuroanatomical nature of this auditory-locomotor pathway is a major step towards understanding how species-specific anatomical and functional properties of this pathway may underpin success rate of kangaroo rats in the wild. To evaluate the anatomical connectivity, a trans-synaptic retrograde pseudorabies virus was injected into the right gastrocnemius muscle and induces the expression of green fluorescent protein in all presynaptic neurons that are synaptically connected to the afferent motor neuron of the muscle, whether they be motor or not. Following 5-7 days of recovery after viral injection, kangaroo rats were euthanized, and their brains removed, frozen and sectioned coronally. Tissue sections containing all central auditory nuclei were then mounted directly onto slides or immunohistochemically labeled to amplify visibility of GFP expression. Sections were imaged through a microscope where GFP expression was observed in motor nuclei within the brainstem and midbrain along with the cochlear nucleus, a key site for mediating the acoustic startle response.
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