Role of GABAB receptors in the control of hypoglossal motoneurons in vivo.
There is little information on GABAB receptor-mediated effects on orofacial motoneurons. We recorded the inspiratory activity from both hypoglossal (XII) nerves in urethane-anesthetized, paralyzed, vagotomized and artificially ventilated rats. A GABAB receptor agonist, baclofen, or antagonist, CGP-35348, was microinjected into one XII nucleus. Baclofen rapidly reduced the XII nerve activity in a dose-dependent manner by over 50%. The antagonist caused a delayed suppression of activity by 40%. We conclude that: (1) GABAB receptors within the XII nucleus may suppress the activity of inspiratory XII motoneurons, but they are not tonically active under the conditions of our experiment; (2) there is a net endogenous excitatory effect in XII motoneurons that is mediated by GABAB receptors located in the reticular formation surrounding the XII nucleus.
Okabe
S
S
Department of Medicine, School of Veterinary Medicine, University of Pennsylvania, Philadelphia 19104.
Woch
G
G
Kubin
L
L
D000818:Animals; D001418:Baclofen / Q000494:pharmacology; D001794:Blood Pressure / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D018756:GABA Antagonists / Q000494:pharmacology; D007002:Hypoglossal Nerve / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D008845:Microinjections; D009046:Motor Neurons / Q000187:drug effects / Q000502:physiology*; D009943:Organophosphorus Compounds / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D018079:Receptors, GABA / Q000145:classification / Q000187:drug effects / Q000502:physiology*; D012119:Respiration / Q000187:drug effects
D018756:GABA Antagonists; D009943:Organophosphorus Compounds; D018079:Receptors, GABA; C066430:CGP 35348; D001418:Baclofen