ENDURANCE TRAINING EFFECTS ON NEUROTRANSMITTER RELEASE IN RAT STRIATUM - AN IN-VIVO MICRODIALYSIS STUDY

In the present study we use the in vivo microdialysis sampling techniq ue to register extracellular levels of neurotransmitters in the striat um of trained and untrained rats. We further evaluate the influence of 1 h of exercise on the striatal release of dopamine (DA), noradrenali ne (NA), glutamate (GLU) and gamma-aminobutyric acid (GABA) in trained and untrained rats. Male Wistars were randomly assigned to a training or control group. The exercise training consisted of running on a tre admill for 6 weeks, 5 days week(-1), with running time and speed gradu ally increased from 30 min at 19 m min(-1) during the first week to 80 min at 26 m min(-1) during the final training week. The animals of th e control group were placed on the treadmill twice a week, and receive d a total of four 'adaptation sessions', in which they exercised 15-45 min at 26 m min(-1). Brain dialysates were analysed with microbore li quid chromatography (LC), with electrochemical detection (monoamines a nd GABA) and fluorescence detection (GLU). Soleus citrate synthase and basal striatal concentrations of DA, NA and GLU were significantly di fferent between the trained and control animals. Sixty minutes of exer cise significantly increased extracellular DA, NA and GLU levels in bo th groups, but there was no statistically significant difference in th e exercise-induced increase between trained and control animals. There was no statistical difference in basal or exercise-induced GABA level s between trained and control animals. The results indicate that exerc ise training appears to result in diminished basal activity of striata l neurotransmitters, while maintaining the necessary sensitivity for r esponses to acute exercise.