Neuroscience
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Metabotropic glutamate receptors (mGluRs) are widely expressed throughout the central nervous system. They are linked to G-protein coupled receptors and are known to modulate synaptic transmission. The data regarding their expression in auditory structures are not systematic and mainly originate from physiological studies where expression was used to support physiological findings. ⋯ In the AC, the staining was more intense near the surface and diminished toward white matter. We also found that the overall expression level of mGluR2/3 was increased significantly in aged animals in all auditory structures tested. Collectively, our detailed immunostaining findings suggest that the group II mGluRs are widely expressed throughout the central auditory system and their contribution to auditory processing increases with age.
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Corticotropin-releasing factor (CRF) is an important stress hormone, and because of the different distributions and functions of its receptors, CRF has various effects on the stress response of animals. CRF receptor 2 (CRFR2) is a functional receptor of CRF that may be related to appetite regulation and sex differences. In this study, male and female C57BL/6 mice were exposed to an ambient temperature of 4 °C, and feed intake were determined. ⋯ As a result, 1) there were only significant changes in 2 h feed intake and rectal temperature in males; 2) neuronal excitability was elevated in the paraventricular thalamus (PVT) and paraventricular hypothalamic nucleus (PVH) brain regions of both male and female mice; 3) serum corticosterone and the expression of corticosterone receptors in the PVH were elevated in males but not in females; 4) the activation of the CRFR2 signal in the PVT and PVH brain regions differed by sex: the expression of CRFR2 was upregulated in male mice, and the phosphorylation of protein kinase B (AKT) and cAMP-response element binding protein (CREB) was significantly reduced; and 5) the cold-evoked eating behavior of male mice was abolished when CRFR2 in the PVT was knocked down. In summary, we conclude that male mice are more sensitive to cold stress than are female mice. The CRFR2/AKT/CREB signaling pathway in the PVT and PVH may mediate sex differences in the eating behavior of cold-exposed mice.
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Prepulse inhibition (PPI) refers to the phenomenon in which a weak sensory stimulus before a strong one significantly reduces the startle reflex caused by the strong stimulus. Perceptual spatial separation, a phenomenon where auditory cues from the prepulse and background noise are distinguished in space, has been shown to enhance PPI. This study aims to investigate the neural modulation mechanisms of PPI by the spatial separation between the prepulse stimulus and background noise, particularly in the deep superior colliculus (deepSC). ⋯ The prepulse stimulus was a segment of narrowband noise, with interaural time differences adjusted so that the prepulse stimulus and background noise were perceived as either ipsilaterally leading or contralaterally leading, resulting in perceptual spatial fusion or spatial separation. The results showed that under conditions of spatial separation, the stimulus-response coherence of the envelope and fine structure components of the prepulse stimulus in the deepSC was significantly enhanced, the response of the deepSC to the stimulus was significantly reduced in the presence of the prepulse stimulus, and the envelope component of the prepulse stimulus was positively correlated with the inhibitory effect. The above results suggest that perceptual spatial dissociation can significantly enhance the expression of deepSC, particularly the precision of the envelope component, thereby significantly affecting the electrophysiological response of PPI.