Induction of presynaptic reexpression of an adhesion protein in lamina II after dorsal root deafferentation in adult rat spinal cord.
Limbic system-associated membrane protein (LAMP), a 64-kDa membrane protein, is an axon guidance adhesion molecule expressed by neurons in limbic system-related areas of the CNS. During development, LAMP is expressed on growing axons, growth cones, and their target neurons, but in adults it is restricted to membranes of somata and dendrites. In the adult spinal cord, LAMP immunoreactivity is found only on neurons of lamina II, lamina X, and the intermediolateral cell column and its ultrastructural localization is entirely postsynaptic. We studied changes in the expression of LAMP in lamina II of adult rat spinal cord after L1-S2 dorsal rhizotomy, a procedure that partially deafferents lamina II neurons and induces axonal sprouting by spared systems in lamina II. At the light microscopic level, LAMP immunoreactivity in lamina II was decreased in density at 3, 10, and 60 days postoperatively. This decrease in immunoreactivity suggests that LAMP expression by lamina II neurons may normally be regulated by specific afferent activity. Ultrastructurally, in control lamina II and after deafferentation in both control and deafferented lamina II at 3 and 60 days postoperatively, LAMP expression was restricted to postsynaptic membranes. Ten days after deafferentation, however, when axons are actively sprouting, LAMP was expressed on both axonal and postsynaptic membranes. The reexpression of LAMP on axonal profiles after deafferentation may identify axons that undergo sprouting in response to deafferentation.
Zhang
B
B
Department of Neurobiology and Anatomy, Allegheny University of the Health Sciences, Philadelphia, Pennsylvania 19129, USA.
Levitt
P
P
Murray
M
M
D000344:Afferent Pathways / Q000502:physiology; D000818:Animals; D001369:Axons / Q000502:physiology / Q000648:ultrastructure; D015816:Cell Adhesion Molecules, Neuronal / Q000096:biosynthesis*; D003712:Dendrites / Q000502:physiology / Q000648:ultrastructure; D005260:Female; D058851:GPI-Linked Proteins; D007150:Immunohistochemistry; D009416:Nerve Regeneration; D009474:Neurons / Q000166:cytology / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D019051:Rhizotomy; D012701:Serotonin / Q000032:analysis; D013116:Spinal Cord / Q000502:physiology*; D013126:Spinal Nerve Roots / Q000502:physiology*; D013373:Substance P / Q000032:analysis; D013569:Synapses / Q000502:physiology* / Q000648:ultrastructure
D015816:Cell Adhesion Molecules, Neuronal; D058851:GPI-Linked Proteins; C095362:limbic system-associated membrane protein; D012701:Serotonin; D013373:Substance P