RESUMEN
We used immunohistochemical methods to quantify changes in the number of glycine-immunoreactive neurons of the dorsomedial, lateral and cerebrospinal fluid contacting cell populations of the spinal cord of larval sea lampreys after a complete spinal cord injury. The data presented here are quantifications of the number of glycine-immunoreactive neurons located in the rostral and caudal stumps of the spinal cord and the corresponding statistical analyses. These data show that, glycine immunoreactivity is lost in glycinergic neurons immediately after injury and that the number of glycine-immunoreactive neurons is recovered in the following two weeks. These data are useful for researchers investigating determinants that underlie the spontaneous recovery of locomotion following spinal injuries in regenerating animal models, and for analysing the role of glycinergic neurons in spinal cord repair after an injury.
RESUMEN
In contrast to mammals, the spinal cord of lampreys spontaneously recovers from a complete spinal cord injury (SCI). Understanding the differences between lampreys and mammals in their response to SCI could provide valuable information to propose new therapies. Unique properties of the astrocytes of lampreys probably contribute to the success of spinal cord regeneration. The main aim of our study was to investigate, in the sea lamprey, the release of aminoacidergic neurotransmitters and the subsequent astrocyte uptake of these neurotransmitters during the first week following a complete SCI by detecting glutamate, GABA, glycine, Hu and cytokeratin immunoreactivities. This is the first time that aminoacidergic neurotransmitter release from neurons and the subsequent astrocytic response after SCI are analysed by immunocytochemistry in any vertebrate. Spinal injury caused the immediate loss of glutamate, GABA and glycine immunoreactivities in neurons close to the lesion site (except for the cerebrospinal fluid-contacting GABA cells). Only after SCI, astrocytes showed glutamate, GABA and glycine immunoreactivity. Treatment with an inhibitor of glutamate transporters (DL-TBOA) showed that neuronal glutamate was actively transported into astrocytes after SCI. Moreover, after SCI, a massive accumulation of inhibitory neurotransmitters around some reticulospinal axons was observed. Presence of GABA accumulation significantly correlated with a higher survival ability of these neurons. Our data show that, in contrast to mammals, astrocytes of lampreys have a high capacity to actively uptake glutamate after SCI. GABA may play a protective role that could explain the higher regenerative and survival ability of specific descending neurons of lampreys.
