Brain research
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Intra-axonal recording and horseradish peroxidase (HRP) injection techniques were employed to define the response properties of periodontal mechanoreceptive afferents originating from the trigeminal mesencephalic nucleus (Vmes) and their morphological characteristics. The periodontal Vmes neurons were classified into two types: slowly adapting (SA) and fast adapting (FA) types. The central terminals of 7 SA and 4 FA afferents were recovered for detailed analyses. ⋯ The average size of somata and mean diameters of U fibers and main collaterals from C fiber were significantly larger in SA neurons than FA neurons. The average size of fiber varicosities became smaller in the following nuclei, Vmo, Vsup, Vp, Vint and Vo.r, but not significant between the two functional types. The functional role of the periodontal Vmes afferents to jaw reflexes was discussed particularly with respect to their central projection sites in the brainstem nuclei.
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We applied tests of antidromic activation to identify cells in the hamster intergeniculate leaflet (IGL) that project to either the suprachiasmatic nucleus (SCN) or the contralateral IGL. IGL cells projecting to these targets were tested for photic responses; most showed sustained activation, while a few were suppressed by retinal illumination. Stimulation of one IGL typically suppressed firing in contralateral IGL cells and inhibited responses to immediately succeeding photic stimulation.