Biology subjects

Warren, B.

Publications and source records attributed to Warren, B..

3 recordsLinked to original sources

bioRxiv2022

Labeled lines for fat and sugar reward combine to promote overeating

Food is a powerful natural reinforcer that guides feeding decisions. The vagus nerve conveys internal sensory information from the gut to the brain about nutritional value; however, the cellular and molecular basis of macronutrient-specific reward circuits are poorly understood. Here, we monitor in vivo calcium dynamics to provide direct evidence of independent vagal sensing pathways for detection of dietary fats and sugars. Using activity-dependent genetic capture of nutrient-specific vagal neurons activated in response gut infusions, we demonstrate the existence of separate hard-wired reward circuits for fat and sugar that are necessary and sufficient for nutrient-specific reinforcement. Even when controlling for calories, combined activation of fat and sugar circuits increases overeating compared to fat or sugar alone. This work provides new insight on the complex sensory circuitry that mediates motivated behavior and suggests that a subconscious internal drive to consume obesogenic diets (e.g., those high in both fat and sugar) may impede conscious dieting efforts.

neuroscience↗

bioRxiv2021

Physiological changes throughout the ear due to age and noise - a longitudinal study

Biological and mechanical systems, whether by their overuse or their aging, will inevitably fail. Hearing provides a poignant example of this with noise-induced and age-related hearing loss. Hearing loss is not unique to humans, however, and is experienced by all animals in the face of wild and eclectic differences in ear morphology and operation. Here we exploited the high throughput and accessible tympanal ear of the desert locust, Schistocerca gregaria (mixed sex) to rigorously quantify changes in the auditory system due to noise exposure (3 kHz pure tone at 126 dB SPL) and age. We analysed tympanal dispalcements, morphology of the auditory Mullers organ and measured activity of the auditory nerve, the transduction current and electrophysiological properties of individual auditory receptors. We found that noise mildly and transiently changes tympanal displacements, decreases both the width of the auditory nerve and the transduction current recorded from individual auditory neurons. Whereas age - but not noise - decreases the number of auditory neurons and increases their resting potential. Multiple other properties of Mullers organ were unaffected by either age or noise including: the number of supporting cells in Mullers organ or the nerve, membrane resistance and capacitance of the auditory neurons. The sound-evoked activity of the auditory nerve decreased as a function of age and this decrease was exacerbated by noise, with the largest difference during the middle of their life span. This middle-aged deafness pattern of hearing loss mirrors that found for humans exposed to noise early in their life. Key point summaryO_LIAge and noise lead to hearing loss. C_LIO_LITympanal displacements have a transient and delayed reduction after noise. C_LIO_LIThe number of auditory neurons decreases with age. The width of the auditory nerve is reduced with noise exposure. C_LIO_LILocusts repeatedly exposed to noise lost their hearing compared to silent controls, but their hearing became similar to old silent control locusts due to age-related hearing loss dominating. C_LIO_LIThe electrophysiological properties of the auditory neurons and the transduction current remained unchanged for aged locusts but repeated noise exposure led to a cumulative decrease in the transduction current. C_LI

physiology↗

bioRxiv2019

Physiological Basis of noise-induced hearing loss in a tympanal ear

Acoustic overexposure, such as listening to music too loud and too often, results in noise-induced hearing loss. The pathologies of this prevalent sensory disorder begin in the synapses of the primary auditory receptors, their postsynaptic partners and supporting cells. The extent of noise-induced damage, however, is determined by over-stimulation of primary auditory receptors. When over-stimulated, an excessive amount of positive ions flood into the primary auditory receptors, triggering the activation of ion channels and possibly disrupting their ability to encode sound. A systematic characterisation of the electrophysiological function of primary auditory receptors is warranted to understand how noise-exposure impacts on downstream targets, where the pathologies of hearing loss begin. Here, we used the experimentally-accessible locust ear to characterise noise-induced changes in the auditory receptors. Although, we found a decrease in ability of the primary auditory neurons to encode sound, this is probably due to pathologies of their supporting cells.

neuroscience↗