7^e Colloque de la Société des neurosciences

May 18-20, 2005, Lille (France)

For lectures and symposia, time indicates the beginning of the session.
For posters, authors are expected to be present at the time indicated.

Poster F-43 - 19/05/05, 15:00 - Lille Métropole I
Session F - Neurophysiology I
Ref.: 7^e Colloque de la Société des neurosciences, Lille 2005, F.43.

Author(s)	Gestreau C. (1), Obled S. (2) & Dutschmann M. (3)
Addresse(s)	(1) Lab Physio NeuroVégét, Marseille, France ; (2) Service Gastro-Entéro, CHU Nîmes, France ; (3) Dept Physio, Göttingen, Allemagne
Title	The Kölliker-Fuse nucleus controls XII motoneurons during breathing and swallowing: preliminary results from the decerebrate rat and the working heart-brainstem preparation (WHBP).
Text	Tongue movements must be rapidly and accurately adjusted in response to the demands of multiple complex motor tasks including licking/mastication, swallowing, vocalization, breathing and protective reflex such as coughing. Yet, central mechanisms responsible for motor and premotor control of hypoglossal (XII) activity are still largely unknown. In this study, our aims were to evaluate to what extent the Kölliker-Fuse nucleus (KFN) contribute to the respiratory- as well as the swallowing-related activities of XII motoneurons in the rat. In a first series of experiments, we used the in situ WHBP of rat to elucidate the role of the KFN in controlling retrusor XII motoneurons during breathing. Chemical activation of neurons was achieved after injection (40 nl, 10 mmol) of glutamate into the right KFN, while activities were recorded from the phrenic and XII nerves. Glutamate placed in the intermediate portion of the KFN (n=5) produced inspiratory termination and a transient prolongation of the expiratory period (apnea). This was clearly accompanied by a complete suppression of phasic inspiratory-related discharges in the lateral branch of the XII nerve. Vehicle injections did not induced changes in phrenic and/or XII activities. In a second series of experiments, decerebrate rats (n=5) were used to evaluate the effect of electrolytic lesions of the KFN (n=10) on both breathing- and swallowing-related activity of XII motoneurons. Swallows were induced by mechanical stimulation of the pharyngeal mucosa while recordings were made from both XII nerves. Unilateral destruction of the KFN induced bilateral increases (50 to 150%) in breathing and swallowing-related bursts of XII activity. These experiments strongly suggest a prominent role for the KFN in XII motor control associated not only with breathing but also with ingestive (swallowing) behaviors. They suggest a functional inhibitory control from KFN onto XII motoneurons.