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  • 1
    Electronic Resource
    Electronic Resource
    Identification of the medullary swallowing regions in the rat (1985)
    Springer
    Experimental brain research 57 (1985), S. 256-263 
    Details
    ISSN: 1432-1106
    Keywords: Swallowing ; Medullary swallowing neurons ; Nucleus of the solitary tract ; Unit activity (extracellular microelectrodes) ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The aim of the present study was to identify the central structures involved in the organization of the swallowing reflex in the rat. Using concentric bipolar electrodes, the medulla and pons were systematically explored in order to determine which central areas responded to stimulation by inducing swallowing. These areas, which were located in the dorsal medulla oblongata, were the solitary tract, the nucleus of the solitary tract (NST) and the adjacent reticular formation. Stimulation of the ventral ponto-medullary regions was ineffective with regard to the initiation of the swallowing reflex. The activity of medullary swallowing neurons was recorded using extracellular microelectrodes. These swallowing neurons responded with a burst of spikes (swallowing activity) which was closely linked to the swallowing reflex elicited by stimulation of the superior laryngeal nerve (SLN). Under SLN stimulation, the activity of some of the swallowing neurons furthermore showed an initial response consisting of 1 or 2 spikes after a brief latency. According to their location and the latency of their initial response, swallowing neurons were divided into two groups. Group I neurons were located in a dorsal area of the medulla oblongata corresponding to the NST and the adjacent reticular formation. All these neurons exhibited an initial response with a very short latency (1 to 4 ms), the swallowing activity of most of these neurons started before the onset of the swallowing motor sequence. Group II neurons were located either in a ventral area corresponding to the nucleus ambiguus and the surrounding reticular formation or in a dorsal and medial area corresponding to the hypoglossal nucleus and its vicinity. Some of these neurons also exhibited an initial response to SLN stimulation, but with a longer latency (7–12 ms). Motor paralysis of the animal (performed by curare injection) did not affect the swallowing activity of the neurons belonging to either group. Thus, the swallowing activity of the medullary neurons studied was a truly central activity. It is concluded that the swallowing neurons studied belonged to the medullary swallowing center; the group II neurons were motoneurons and interneurons forming the efferent stage of the swallowing center, and the group I neurons were the interneurons which largely belong to the center which programs the swallowing motor sequence.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00236530
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Swallowing responses induced by microinjection of glutamate and glutamate agonists into the nucleus tractus solitarius of ketamine-anesthetized rats (1990)
    Springer
    Experimental brain research 83 (1990), S. 151-158 
    Details
    ISSN: 1432-1106
    Keywords: Swallowing ; Nucleus tractus solitarius ; Excitatory amino acids ; Ketamine anesthesia ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Swallowing is a patterned motor activity generated by neurons located within the nucleus tractus solitarius (NTS). An excitatory amino acid (EAA) neurotransmitter, such as glutamate (GLU), is suspected of being involved in the initiation of swallowing by NTS neuronal components. However, swallowing can still be elicited in animals anesthetized with ketamine, an antagonist of the N-methyl-D-aspartate (NMDA) subclass of EAA receptors. The present experiments were therefore designed to investigate the influence of EAA administration within the NTS on the swallowing motor acitivity of rats anesthetized with ketamine. Pressure microinjections of GLU in doses ranging from 25 to 500 pmol elicited swallowing. This effect was dose-dependent and was not reproduced when control injections of the vehicle solution were performed. Microinjections of the GLU agonists, quisqualate (QUIS) and NMDA, in doses ranging between 2.5 and 50 pmol, also induced swallowing motor activities. QUIS, like GLU, elicited a short series of swallows at a brief latency while NMDA generated long-lasting rhythmic swallowing with a longer latency. Swallowing induced by GLU microinjections (100 pmol) was suppressed almost completely by local pretreatment with either the broad spectrum EAA receptor antagonist, gamma-D-glutamylglycine (250 pmol), or the more selective non-NMDA antagonist, 6-cyano-7-nitroquinoxaline-2,3-dione (50–100 pmol), but not by pretreatment with the selective NMDA antagonist, DL-2-amino-5-phosponovalerate (250 pmol). On the other hand, pretreatment with DL-2-amino-5-phosphonovalerate (50 pmol) suppressed the deglutitions induced by NMDA microinjections (10 pmol) but not those elicited by QUIS microinjections (10 pmol). These results provide evidence that swallowing can be induced by activation of EAA receptors of both the NMDA and the non-NMDA subclasses located within the NTS. Furthermore they indicate that both subclasses may still be active in ketamine-anesthetized animals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00232203
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
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