Contractile and Histochemical Properties of the Inferior Oblique Muscle in the Rat and in the Cat

Abstract

Mechanical and histochemical properties of inferior oblique muscles(IO) were compared in adult albino rat and pigmented cat. The twitch contraction times and the fusion frequencies were about the same in both species indicating similar contractile properties of the fast contracting fibers. Rat IO seemed to contain fewer slowly contracting fibers than cat IO; half-decay time of the twitch was shorter in rat than in cat muscles and fusion started at higher stimulus frequencies. Fatique resistance was lower in rat than in rat than in cat. Post-tetanic potentiation occurred in the cat but not in the rat IO. Almost all fibers of rat IO were rich in myofibrillar ATPase. In cat IO most fibers showed high myofibrillar ATPase activity, but some fibers in the global layer had moderate to small amounts of this enzyme. This correlates well with the physiological differencies between cat and rat IO.

Tonic and phasic components of eye movements during REM sleep in the rat

“…Extraocular muscles in rats are mainly composed of fast‐contracting and low fatigue‐resistant twitch fibres, which account for up to 90% of the global and 80% of the orbital layer (Mayr, 1971), suggesting that extraocular musculature in rats is adapted to phasic activity. Compared with rats, extraocular muscles in cats show a less proportion of fast‐contracting fibres, suggesting that they are more specialized in fatigue resistance but slow response (Pilar, 1967; Hanson & Lennerstrand, 1977). These anatomical differences correlate with the species’ respective oculomotor behaviours, and could explain why rats perform faster saccadic eye movements than cats during wakefulness and REM sleep.…”

Contractile Properties of Extraocular Muscle in Siamese Cat

“…(40 mg/kg b.w.). Previous papers by Hanson & Lennerstrand (1977) and Lennerstrand & Hanson (1978a, 1979 have given detailed descriptions on (1) the preparation of the inferior oblique muscle for isometric tension recording to single and repetitive stimulation of the muscle nerve, (2) the force sensing system and (3) the stimulus procedures to study speed of contraction in twitch and tetanus, fatigue properties and post-tetanic potentiation. The rapid tension changes were recorded on a storage oscilloscope (Tektronix 5 103 N), and the responses with a slower time course on an ink-writer (Beskman Model RB), which was sufficient for resolving the slow tension changes during fatigue stimulations.…”

Contractile properties and histochemistry of extraocular muscle in the pigmented and the albino guinea pig

“…The contractile properties of eye muscles in albino rat has previously been studied (Hanson & Lennerstrand 1977). Twitch characteristics and the tetanic fusion frequency were similar to those found in the albino guinea pig, but the fatigue resistance to a 200 Hz stimulation was lower (10%) than in the guinea pigs (18%).…”

“…The tendon of the muscle was attached to a sensitive strain gauge for isometric tension recording. The activation of the muscle over the nerve with single shocks and trains of pulses and the recording of the tension responses were performed in the same manner as described in our previous studies on eye muscle (Hanson & Lennerstrand 1977;Lennerstrand & Hanson 1979). The measurements o n twitch and tetanic responses have been described elsewhere (Hanson & Lennerstrand 1977), and are summarized in Fig.…”