Direct projections from the nucleus retroambiguus to cricothyroid motoneurons in the cat.
Vocalization can be elicited by stimulation in the periaqueductal gray (PAG). Light-microscopical tracing and physiological studies have revealed that the PAG uses the nucleus retroambiguus (NRA) as a relay to excite the vocalization muscle motoneurons. Direct NRA projections have been demonstrated to pharyngeal and abdominal wall muscle motoneurons, but not to laryngeal motoneurons. In two cats 0.1% cholera toxin subunit b was injected in the cricothyroid muscle of the larynx to retrogradely label its motoneurons, and 2.5% wheat germ agglutinin-horseradish peroxidase was injected into the NRA to anterogradely label its fibers. The electronmicroscopical results indicate that the NRA fibers make monosynaptic contacts with cricothyroid motoneuronal dendrites. Almost all NRA terminal profiles had asymmetrical synapses and contained mostly round or pleiomorphic vesicles, which strongly suggests that the NRA-cricothyroid motoneuronal projection is an excitatory pathway.
Boers
J
J
Department of Anatomy and Embryology, Faculty of Medicine, University of Groningen, A. Deusinglaan 1, 9700 AD Groningen, The Netherlands.
Klop
E M
EM
Hulshoff
A C
AC
de Weerd
H
H
Holstege
G
G
D000818:Animals; D002415:Cats; D002772:Cholera Toxin / Q000378:metabolism; D004525:Efferent Pathways / Q000502:physiology / Q000648:ultrastructure*; D007150:Immunohistochemistry; D007821:Laryngeal Muscles / Q000294:innervation* / Q000502:physiology; D007823:Laryngeal Nerves / Q000502:physiology / Q000648:ultrastructure*; D008526:Medulla Oblongata / Q000502:physiology / Q000648:ultrastructure*; D008854:Microscopy, Electron; D009046:Motor Neurons / Q000502:physiology / Q000648:ultrastructure*; D010487:Periaqueductal Gray / Q000166:cytology / Q000502:physiology; D017729:Presynaptic Terminals / Q000502:physiology / Q000648:ultrastructure; D012143:Respiratory Physiological Phenomena; D013116:Spinal Cord / Q000502:physiology / Q000648:ultrastructure*; D014828:Vocalization, Animal / Q000502:physiology*; D018998:Wheat Germ Agglutinin-Horseradish Peroxidase Conjugate
D018998:Wheat Germ Agglutinin-Horseradish Peroxidase Conjugate; D002772:Cholera Toxin