Cutaneus trunci muscle reflex of the guinea pig

Abstract

The cutaneus trunci muscle reflex in guinea pigs was studied with a combination of video analysis, electromyography, lesioning, and light microscopy. The muscle forms a bilateral, subdermal sheet over much of the trunk. Local contractions of the dorsal part of the muscle are produced in response to brief tactile or electrical stimulation of the skin and consist of a twitch centered 1-2 cm rostral of the stimulus site. The reflex receptive field covers most of the thoracic and lumbar dorsal surface. The sensory information is carried via segmental dorsal cutaneous nerves. Receptive fields of adjacent nerves overlap and form rectangular areas perpendicular to the midline, at thoracic levels. Motor innervation projects through the lateral thoracic nerves of the brachial plexus. The motoneurons are located near the cervical thoracic junction (C7-T1). Lesions of the lower thoracic cord indicate that ascending sensory information is carried to the motor nuclei via the ventral half of the lateral funiculus. This pathway conveys information primarily from ipsilateral skin. There is a weaker input from contralateral skin, crossing at segmental levels. Electromyographic responses to brief electrical stimulation of lower thoracic skin occur usually as 10-12 msec bursts at latencies of 10-20 msec, and do not readily habituate or fatigue at stimulus frequencies below 10 Hz. The reflex persists under light pentobarbital anesthesia. This combination of characteristics makes the reflex useful for a variety of physiological and pathophysiological studies.

Topographical Anatomy of the Equine M. Cutaneus Trunci in Relation to the Position of the Saddle and Girth

“…In guinea pigs, it has been shown that the twitch response does not readily habituate or fatigue at stimulus frequencies below 10 Hz [3]. Similarly, isolated rat m. cutaneus trunci continues to contract in response to repeated electrical stimulations over a period of several hours [24].…”

“…M. cutaneus trunci has been described in detail in the cat [9], dog [9,10], and guinea pig [3]. However, descriptions of the equine m. cutaneus trunci are inconsistent in terms of its size and shape, especially the dorsal profile that extends toward the panels of the saddle and the orientation of its fibers [1,2,[11][12][13].…”

“…It is so intimately adherent to the skin [1] that it is usually removed with the skin during dissection [2]. Typically, the cutaneous muscles are found in areas of the skin of quadrupeds that are inaccessible to scratching [3]. In response to touching the skin overlying m. cutaneus trunci, horses exhibit a skin twitch or panniculus reflex, the purpose of which is to dislodge irritants from the skin surface.…”

Effects of methylprednisolone and 4-chloro-3-hydroxyanthranilic acid in experimental spinal cord injury in the guinea pig appear to be mediated by different and potentially complementary mechanisms

“…It is therefore likely that 4-Cl-3-HAA has a longer therapeutic window than MP, because the peak of QUIN accumulation does not occur until 12 days after injury. 25 These indications should [26][27][28] be considered when and if therapeutic interventions targeting QUIN accumulation are tested clinically.…”

Myoelectric Evoked Potentials Versus Locomotor Recovery in Chronic Spinal Cord Injured Rats

“…One may conclude that forelimb function (and supraspinal function in general) can be significantly affected by more caudal spinal lesions, and this factor should be taken into consideration in evaluating recovery. Indeed, the cutaneous trunci muscle reflex provides a mechanism for transmitting information across the lesion site extraspinally, since the trunk muscles can be controlled from above the lesion while the sensory response to muscle contraction would enter below the lesion (Blight et al, 1990). It has been established that increasing general sensory input to the spinal cord can facilitate descending activation of motoneurons (Dimitrijevic, 1988).…”