Anatomic and physiological characteristics of the ferret lateral rectus muscle and abducens nucleus.
J Appl Physiol (1985)
; 103(5): 1706-14, 2007 Nov.
Article
en En
| MEDLINE
| ID: mdl-17717110
ABSTRACT
The ferret has become a popular model for physiological and neurodevelopmental research in the visual system. We believed it important, therefore, to study extraocular whole muscle as well as single motor unit physiology in the ferret. Using extracellular stimulation, 62 individual motor units in the ferret abducens nucleus were evaluated for their contractile characteristics. Of these motor units, 56 innervated the lateral rectus (LR) muscle alone, while 6 were split between the LR and retractor bulbi (RB) muscle slips. In addition to individual motor units, the whole LR muscle was evaluated for twitch, tetanic peak force, and fatigue. The abducens nucleus motor units showed a twitch contraction time of 15.4 ms, a mean twitch tension of 30.2 mg, and an average fusion frequency of 154 Hz. Single-unit fatigue index averaged 0.634. Whole muscle twitch contraction time was 16.7 ms with a mean twitch tension of 3.32 g. The average fatigue index of whole muscle was 0.408. The abducens nucleus was examined with horseradish peroxidase conjugated with the subunit B of cholera toxin histochemistry and found to contain an average of 183 motoneurons. Samples of LR were found to contain an average of 4,687 fibers, indicating an LR innervation ratio of 25.61. Compared with cat and squirrel monkeys, the ferret LR motor units contract more slowly yet more powerfully. The functional visual requirements of the ferret may explain these fundamental differences.
Buscar en Google
Banco de datos:
MEDLINE
Asunto principal:
Nervio Abducens
/
Puente
/
Movimientos Oculares
/
Hurones
/
Neuronas Motoras
/
Contracción Muscular
/
Músculos Oculomotores
Tipo de estudio:
Prognostic_studies
Límite:
Animals
Idioma:
En
Año:
2007
Tipo del documento:
Article