Induction of Fos protein immunoreactivity by spinal cord contusion

Abstract

The objective of the present study was to identify neurons in the central nervous system that respond to spinal contusion injury in the rat by monitoring the expression of the nuclear protein encoded by the c-fos gene, an activity-dependent gene, in spinal cord and brainstem regions. Rats were anesthetized with urethane and the injury was produced by dropping a 5-g weight from 20.0 cm onto the exposed dura at the T10-L1 vertebral level (contusion group). The spinal cord was exposed but not lesioned in anesthetized control animals (laminectomy group); intact animals were also subjected to anesthesia (intact control). Behavioral alterations were analyzed by Tarlov/ Bohlman scores, 2 h after the procedures and the animals were then perfused for immunocytochemistry. The patterns of Fos-like immunoreactivity (FLI) which were site-specific, reproducible and correlated with spinal laminae that respond predominantly to noxious stimulation or injury: laminae I-II (outer substantia gelatinosa) and X and the nucleus of the intermediolateral cell column. At the brain stem level FLI was detected in the reticular formation, area postrema and solitary tract nucleus of lesioned animals. No Fos staining was detected by immunocytochemistry in the intact control group. However, detection of FLI in the group submitted to anesthesia and surgical procedures, although less intense than in the lesion group, indicated that microtraumas may occur which are not detected by the Tarlov/ Bohlman scores. There is both a local and remote effect of a distal contusion on the spinal cord of rats, implicating sensory neurons and centers related to autonomic control in the reaction to this kind of injury.

Establishment and assessment of a simple and easily reproducible incision model of spinal cord neuron cells in vitro

“…IEGs have been used to monitor neuronal responds to peripheral nerve and spinal cord injury (Yakovlev and Faden 1994;Broude et al 1997;Ruggiero et al 1997;Del-Bel et al 2000). Fos and Jun have most often been used as histological markers for neuronal activation as they are induced by a wide range of mechanical stimuli, including spinal cord transection, sciatic nerve chronic constriction injury, sciatic nerve transection, sciatic nerve crush, and noxious mechanical stimulation (Chi et al 1993;Kajander et al 1996;DunnMeynell and Levin 1997;Ikeda and Nakagawa 1998;Hughes et al 1999).…”

“…Research indicated that at 2.5 h post-transection, a large number of neurons containing c-Fos were observed in spinal transected animals but not in intact animals (Ruggiero et al 1997). For other types of mechanical injury to the spinal cord, such as contusion, the same time course of c-Fos expression was observed (Del-Bel et al 2000). The activation of c-Jun has been correlated with both the regeneration of nerve fibers and the mediation of neuronal death (Ham et al 1995;Hirata et al 1998).…”

Behavioral and physiological methods for early quantitative assessment of spinal cord injury and prognosis in rats

“…Animals were anesthetized by intraperitoneal injection of 250 mg/kg 2,2,2-tribromoethanol (Aldrich Chemical Company Inc., Milwaukee, WI, USA). After shaving the skin, animals were kept in a David Kopf stereotaxic apparatus and an incision was made in the skin and underlying muscles of the mid-thoracic region (14). Muscles were retracted and a mid-thoracic laminectomy was performed (vertebral segments T 10 -L 1 ).…”

“…The animals were placed on a hot-plate maintained at 52 ± 0.5ºC. The thermal nociceptive threshold was defined as the time required to elicit a hind paw lick or a jump (14). The cut-off time was 20 s.…”

“…Each rat was placed in a ventilated glass tube with the tail laid across a nickel-chrome wire coil maintained at room temperature (23 ± 2ºC). The coil temperature was then raised at the rate of 9ºC/s by the passage of an electric current, adjusted to ensure a tail withdrawal reflex within 2.5 to 3.5 s. A cut-off time of 6 s was established to minimize skin damage (14). Animals were tested for 3 consecutive trials.…”