Neuroscience
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Calbindin D28k-containing non-pyramidal cells were found in all layers and subfields of the hippocampus, with the highest frequency in stratum radiatum of the CA1-CA3 subfields. A large number of these neurons had a vertically oriented dendritic tree, often restricted to to stratum radiatum. In stratum oriens and near to the border of strata radiatum and lacunosum moleculare cells with horizontally running dendrites were also found. ⋯ Here we provide direct evidence that the calbindin-containing non-pyramidal cells were among those projecting to the medial septum. Following horseradish peroxidase injections into the medial septum 80% of the retrogradely labelled non-pyramidal cells were found to be immunoreactive for calbindin D28k, and 20% contained neuropeptide Y. These results suggest that the calbindin D28k-containing and apparently GABA-immunonegative non-pyramidal cells in stratum oriens of the CA1-CA3 regions may also be GABAergic, but have a distant projection, that is, to the medial septum.
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Immunofluorescence and immunogold labeling, together with sucrose gradient separation and Western blot analysis of microsomal subfractions, were employed in parallel to probe the endoplasmic reticulum in the cell body and dendrites of rat cerebellar Purkinje neurons. Two markers, previously investigated in non-nerve cells, the membrane protein p91 (calnexin) and the lumenal protein BiP, were found to be highly expressed and widely distributed to the various endoplasmic reticulum sections of Purkinje neurons, from the cell body to dendrites and dendritic spines. An antibody (denominated anti-rough-surfaced endoplasmic reticulum), which recognized two membrane proteins, p14 and p40, revealed a similar immunogold labeling pattern. ⋯ The latter receptor and the Ca2+ ATPase, known in other species to be concentrated in Purkinje neurons, exhibited bimodal distributions with a peak in the light and another in the heavy subfractions. A similar distribution was also observed with another lumenal protein, protein disulfide isomerase. Taken as a whole, the results that we have obtained suggest the existence in the endoplasmic reticulum of Purkinje neurons of two levels of organization; the first identified by widespread, probably general markers (BiP, p91, possibly p14 and others), the second by specialization markers, such as the inositol 1,4,5-triphosphate receptor and, possibly, p40, which appear restricted to areas where specific functions appear to be localized.
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The possibility that astrocytes participate in the pathophysiology of thermal brain injury caused by systemic heat exposure was examined in conscious young rats. The temporal and regional pattern of the astrocytic response to thermal injury was characterized by demonstrating the immunoreactivity of glial fibrillary acidic protein (GFAP) using monoclonal antibody and avidin-biotin complex technique. Exposure of conscious young animals to heat at 38 degrees C for 4 h in a biological oxygen demand incubator resulted in a marked increase of the GFAP immunoreactivity in specific brain regions as compared with the intact controls. ⋯ The immunostaining in general was seen in the perivascular glia, within the neuropil and the glia limitans. This increase in GFAP immunoreactivity was absent in animals exposed to the same ambient temperature (38 degrees C) for 1 h and 2 h, or at a lower temperature (36 degrees C) for 4 h. These results show that (i) astrocytes actively participate in the pathophysiology of heat stress, (ii) endogenous thermal brain injury elicits activation and hypertrophy of astrocytes ("reactive gliosis") depending on the magnitude and duration of the ambient heat stimulus, and (iii) the astrocytic reaction (observed as increased GFAP immunostaining) could be induced much more rapidly within a very short survival period of 4 h, not reported earlier.
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The transmitter mechanism of a long-lasting descending inhibition of the monosynaptic reflex was investigated in the isolated spinal cord of the neonatal rat. The monosynaptic reflex elicited by dorsal root stimulation was recorded extracellularly from a lumbar ventral root (L3-L5). Electrical stimulation of the upper thoracic part of the hemisected cord caused an inhibition lasting about 40 s of the monosynaptic reflex. ⋯ Besides ketanserin, the descending inhibition was blocked by ritanserin, haloperidol, and pipamperone, which have affinities to 5-hydroxytryptamine2 receptors, and also by spiperone and methiothepin, which are antagonists at both 5-hydroxytryptamine1 and 5-hydroxytryptamine2 receptors (all 1 microM). On the other hand, a 5-hydroxytryptamine1C and 5-hydroxytryptamine2 antagonist, mesulergine (1 microM), and 5-hydroxytryptamine3 antagonists, ICS 205-930 and quipazine (both 1 microM), did not depress either the descending inhibition or the 5-hydroxytryptamine-evoked inhibition of the monosynaptic reflex. The results with these antagonists favor the involvement of 5-hydroxytryptamine2 receptors although the results with mesulergine disagree with this notion. 5-Hydroxytryptamine1 agonists, such as 8-hydroxy-2-(di-n-propylamino)tetralin, buspirone, and 5-carboxyamidotryptamine, and a 5-hydroxytryptamine3 agonist, 2-methyl-5-hydroxytryptamine, induced a long-lasting inhibition of the monosynaptic reflex, which was blocked by ketanserin whereas a 5-hydroxytryptamine2 agonist, S-(+)-alpha-methyl-5-hydroxytryptamine, evoked a biphasic inhibition, in which only the later component was blocked by ketanserin.(ABSTRACT TRUNCATED AT 400 WORDS)