Neuroscience
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Our previous studies showed that the assembly of the GluR6-PSD95-mixed lineage kinase 3 (MLK3) signaling module played an important role in rat ischemic brain injury. In this study, we aimed to elucidate whether ischemic preconditioning could downregulate the assembly of the GluR6-PSD95-MLK3 signaling module and suppress the activation of MLK3, MKK4/7, and c-Jun N-terminal kinase (JNK). ⋯ Taken together, our results indicate that preconditioning can inhibit the over-assembly of the GluR6-PSD95-MLK3 signaling module and the JNK3 activation. GluR6 subunit-containing kainite receptors play an important role in the preconditioning-induced neuronal survival and provide new insight into stroke therapy.
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In the hamster brainstem estrogen receptor-alpha-immunoreactive neurons (ER-alpha-IR) are present in the nucleus para-retroambiguus (NPRA), located in the caudal ventrolateral medulla (CVLM) ventrolaterally to the nucleus retroambiguus (NRA). NPRA neurons project mainly to the thoracic and upper lumbar cord and are probably involved in the autonomic adaptations during the estrous cycle. The periaqueductal gray (PAG), projecting to the CVLM, also contains ER-alpha-IR neurons. ⋯ Our double-immunostudies revealed that ER-alpha-IR projections descend only towards the NPRA and mainly originate from the ipsilateral caudal PAG. Retrogradely labeled ER-alpha-IR neurons in the PAG were observed in two separate columns, laterally and ventrolaterally in the caudal half of the PAG. The results provide evidence for the existence of differentiated PAG-CVLM projections to NRA and NPRA, respectively, originating from discrete longitudinal "PAG-columns." Only the projection to the NPRA is estrogen receptive, supporting the hypothesis that the NPRA is involved in the adaptive changes in autonomic control during successive phases of the estrous cycle.
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Although the mouse is an experimental model with an increasing importance in various fields of neuroscience, the characteristics of its central gustatory pathways have not yet been well documented. Recent electrophysiological studies using the rat and hamster have revealed that taste processing in the brainstem gustatory relays is under the strong influence of inputs from forebrain gustatory structures. In the present study, we investigated the organization of afferent projections to the mouse parabrachial nucleus (PbN), which is located at a key site between the brainstem and gustatory, viscerosensory and autonomic centers in the forebrain. ⋯ Numbers of labeled neurons in the main components of the gustatory system including the insular cortex, bed nucleus of the stria terminalis, central nucleus of the amygdala, lateral hypothalamus, and rostral nucleus of the solitary tract were quantified. These results are basically consistent with those of the previous rat and hamster studies, but some species differences were found. Functional implications of these afferent inputs are discussed with an emphasis on their role in taste.
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Both the firing frequency of primary afferents and neurokinin 1 receptor (NK1R) internalization in dorsal horn neurons increase with the intensity of noxious stimulus. Accordingly, we studied how the pattern of firing of primary afferent influences NK1R internalization. In rat spinal cord slices, electrical stimulation of the dorsal root evoked NK1R internalization in lamina I neurons by inducing substance P release from primary afferents. ⋯ Each pulse in trains at frequencies up to 100 Hz evoked a C-elevation, demonstrating that C-fibers can follow these high frequencies. C-elevation amplitudes declined progressively with increasing stimulation frequency, which was likely caused by a combination of factors including temporal dispersion. In conclusion, the instantaneous firing frequency in C-fibers determines the amount of substance P released by noxious stimuli.