Succinylcholine activation of human horizontal eye muscles.
OBJECTIVE
Succinylcholine (Sch) can induce contracture in slow, multiply innervated muscle fibres of the extraocular muscles in animals of different species. Slow muscle fibres also exist in human eye muscle but their physiological properties have not been studied.


METHODS
Isometric tension development was recorded in the lateral and medial rectus muscles in 12 patients operated under general anaesthesia. A strain gauge probe was attached with 5-0 silk sutures to the muscle tendon. Recordings were made in 12 eye muscles with the tendon attached to the globe and in four muscles detached from the globe. Muscle activation was produced by i.v. injection of Sch at a dose of 0.2-0.3 mg/kg bodyweight.


RESULTS
A single injection of Sch induced slow contractures lasting for several minutes. In the muscles attached to the globe, mean maximal isometric tension was 12.2 g in the lateral rectus and 12.8 g in the medial rectus. Similar tension was shown in the muscles detached from the globe.


CONCLUSIONS
The contracture of eye muscles in response to Sch showed characteristics typical of slow muscle fibre activation in amphibian and avian muscle and confirmed the participation of slow fibre systems in ocular motor control.
Lennerstrand
Gunnar
G
Department of Ophthalmology, Karolinska Institutet, Stockholm, Sweden. Gunnar.Lennerstrand@ste.ki.se
Bolzani
Roberto
R
Tian
Suna
S
Benassi
Mariagrazia
M
Fusari
Maurizio
M
Campos
Emilio
E
Schiavi
Costantino
C
D000293:Adolescent; D000328:Adult; D000768:Anesthesia, General; D005133:Eye Movements / Q000502:physiology; D006801:Humans; D007275:Injections, Intravenous; D007537:Isometric Contraction / Q000187:drug effects / Q000502:physiology*; D008875:Middle Aged; D018657:Muscle Fibers, Slow-Twitch / Q000502:physiology*; D009467:Neuromuscular Depolarizing Agents / Q000494:pharmacology*; D009801:Oculomotor Muscles / Q000187:drug effects / Q000502:physiology*; D013285:Strabismus / Q000503:physiopathology / Q000601:surgery; D013390:Succinylcholine / Q000494:pharmacology*; D013710:Tendons / Q000294:innervation
D009467:Neuromuscular Depolarizing Agents; D013390:Succinylcholine