The Journal of comparative neurology
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The pre-Bötzinger complex (pre-BötC) is a physiologically defined group of ventrolateral medullary neurons that plays a central role in respiratory rhythm generation. These cells are located in a portion of the rostral ventrolateral medulla (RVLM) that is difficult to identify precisely for lack of a specific marker. We sought to determine whether somatostatin (SST) might be a marker for this region. ⋯ In conclusion, the RVLM contains many neurons that express preprosomatostatin mRNA. A subgroup of these cells contains high levels of SST and NK1R immunoreactivity in their somata. These glutamatergic interneurons identify a narrow region of the RVLM that appears to be coextensive with the pre-BötC of adult rats.
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Comparative Study
Saccadic omnipause and burst neurons in monkey and human are ensheathed by perineuronal nets but differ in their expression of calcium-binding proteins.
The extracellular matrix of the brain contains large aggregates of chondroitin sulfate proteoglycans (CSPG), which form lattice-like cell coatings around distinct neuron populations and are termed perineuronal nets. The function of perineuronal nets is not fully understood, but they are often found around neurons containing the calcium-binding protein parvalbumin, suggesting a function in primarily highly active neurons. In the present paper the distribution of perineuronal nets was studied in two functional cell groups of the primate oculomotor system with well-known firing properties: 1) the saccadic omnipause neurons in the nucleus raphe interpositus (RIP) exhibit a high tonic firing rate, which is only interrupted during saccades; they are inhibitory and use glycine as a transmitter; and 2) premotor burst neurons for vertical saccades in the rostral interstitial nucleus of the medial longitudinal fascicle (RiMLF) fire with high-frequency bursts during saccades; they are excitatory and use glutamate and/or aspartate as a transmitter. ⋯ Calretinin was coexpressed in at least 70% of the saccadic burst neurons, but not in the omnipause neurons. Parallel staining of human tissue revealed strongly labeled perineuronal nets around the saccadic omnipause and burst neurons, in corresponding brainstem regions, which specifically highlighted these neurons within the poorly structured reticular formation. These findings support the hypothesis that perineuronal nets may provide a specialized microenvironment for highly active neurons to maintain their fast-spiking activity and are not related to the transmitter or the postsynaptic action of the ensheathed neurons.