DIRECT EVIDENCE FOR THE LINK BETWEEN MONOAMINERGIC DESCENDING PATHWAYS AND MOTOR-ACTIVITY - II - A STUDY WITH MICRODIALYSIS PROBES IMPLANTED IN THE VENTRAL HORN OF THE SPINAL-CORD

In order to define precisely the relation between descending monoamine rgic systems and the motor system, we measured in the ventral horn of spinal cord of adult rats the variations of extracellular concentratio ns of 5-HT, 5-HIAA, DA and MHPG. Measurements were performed during re st, endurance running on a treadmill, and a post-exercise period, with microdialysis probes implanted permanently for 45 days. We found a sl ight decrease in both 5-HT and 5-HIAA during locomotion with a more ma rked decrease during the post-exercise period compared to the mean of rest values. In contrast, the concentration of DA and MHPG increased s lightly during the exercise and decreased thereafter. These results, w hen compared with those of a previous study, which measured monoamines in the spinal cord white matter [C. Gerin, D. Becquet, A. Privat, Dir ect evidence for the Link between monoaminergic descending pathways an d motor activity: I. A study with microdialysis probes implanted in th e ventral funiculus of the spinal cord, Brain Res. 704 (1995) 191-201] , highlight the complex regulation of the release of monoamines that o ccurs in the ventral horn. (C) 1998 Elsevier Science B.V. All rights r eserved.