Primary afferent input to and receptive field properties of cells in rat lumbar area X.
In this study we examined the primary afferent input to rat area X of Rexed, and characterized sensory receptive fields (RFs) of the cells therein. This poorly understood area contains primary afferent fibres, some of which are arranged into a compact bundle beneath the central canal. Anterograde transport of the B fragment of cholera toxin (CTB) from the sciatic nerve showed a strictly ipsilateral projection to segments in L4 and L5 but both ipsi- and contralateral projections in L6 and more caudal segments. The response of cells in area X to mechanical cutaneous stimuli was recorded through extracellular microelectrodes in decerebrate, decerebrate-spinal, and urethane-anaesthetised preparations. The lateral edge of area X was marked by an abrupt change in the RFs: Lateral to area X in the dorsal horn, they were strictly unilateral and relatively small. At a mean of 90 microm from the midline, there was an abrupt expansion of the RFs to cover at least the entire ipsilateral dermatome. Within area X, 70% of the cells' RFs extended across the midline to include contralateral skin. In 35% of cells recorded in rats with intact spinal cords, the RF extended rostrally onto the forelimb. In a small number of cells, the RF included ear pinnae and nose. The precise function of area X cells remains unknown; although they have been shown to be involved in visceral reflexes, the fact that they receive convergent input from a wide variety of tissues and from local and remote body parts implies a more generalized, integrative function.
Wall
Patrick D
PD
Sensory Function Group, Centre for Neuroscience Research, Guy's, King's and St. Thomas' School of Biomedical Sciences, King's College London, Guy's Campus, SE1 1UL London, United Kingdom.
Kerr
Bradley J
BJ
Ramer
Matt S
MS
D000344:Afferent Pathways / Q000502:physiology; D000818:Animals; D003655:Decerebrate State; D004431:Ear, External / Q000502:physiology; D005552:Forelimb / Q000502:physiology; D008159:Lumbar Vertebrae; D008297:Male; D009412:Nerve Fibers / Q000502:physiology; D009474:Neurons / Q000502:physiology*; D009666:Nose / Q000502:physiology; D051381:Rats / Q000502:physiology*; D017207:Rats, Sprague-Dawley; D012677:Sensation / Q000502:physiology; D012879:Skin Physiological Phenomena; D013116:Spinal Cord / Q000166:cytology / Q000502:physiology*