INTRODUCTION: BRAIN-DERIVED NEUROTROPHIC FACTOR (BDNF) AND GLIAL CELL LINE-DERIVED NEUROTROPHIC FACTOR (GDNF) ARE TWO MAIN NEUROTROPHINS THAT IMPROVE MEMORY AND MOTOR FUNCTION BY PROTECTING DOPAMINERGIC, SUBSTANTIA NIGRA AND MOTOR NEURONS (1). ACCUMULATING EVIDENCE HAS SHOWN THAT HYDROGEN PEROXIDE (H2O2) AND TUMOR NECROSIS FACTOR ALPHA (TNF-A) INCREASED EXPRESSION OF BDNF AND GDNF IN DIFFERENT REGIONS OF THE NERVE SYSTEM, HOWEVER, ANTI-INFLAMMATORY AND ANTI-OXIDANT SUPPLEMENTATION REDUCED NEUROTROPHINS (2). FURTHERMORE, INVESTIGATIONS HAVE SHOWN THAT EXERCISE TRAINING WITH LOW TO MODERATE INTENSITY INCREASED BDNF AND GDNF (1, 3). HOWEVER, THE EFFECTS OF INTENSIVE CONTINUOUS AND INTERVAL TRAININGS ON NEUROTROPHINS HAVE NOT YET BEEN WELL ESTABLISHED, ESPECIALLY CONSIDERING THE FACT THAT INTENSIVE EXERCISE TRAINING IS A H2O2 AND TNF-A INDUCER (6, 7). HENCE, THE AIM OF THE PRESENT STUDY WAS TO COMPARE THE EFFECTS OF INTENSIVE CONTINUOUS AND INTERVAL TRAINING ON NEUROTROPHIN CONTENTS IN THE RAT BRAIN.METHODOLOGY: TWENTY-FOUR ADULT ALBINO WISTAR RATS WERE RANDOMLY DIVIDED TO CONTROL, CONTINUOUS AND INTERVAL GROUPS. THE WHOLE BRAIN OF EACH RAT WAS REMOVED FOLLOWING 6 WEEKS OF INTENSIVE CONTINUOUS (80 % VO2MAX) AND INTERVAL (95-100 % VO2MAX) RUNNING ON TREADMILL. BDNF, GDNF AND TNF-A CONTENTS ASSAYS WERE CARRIED OUT BY SANDWICH ELISA KITS AND H2O2 CONCENTRATION WAS CARRIED OUT BY COLORIMETRIC ASSAY KIT. ONE-WAY ANALYSIS OF VARIANCE FOLLOWED BY BONFERRONI POST-HOC WERE USED TO TEST STATISTICAL SIGNIFICANT (P<0.05).RESULTS: H2O2 LEVELS (P=0.01 AND P=0.001, RESPECTIVELY) AND TNF-A (P=0.001 AND P=0.001, RESPECTIVELY), BDNF (P=0.001 AND P=0.001, RESPECTIVELY) AND GDNF (P=0.001 AND P=0.001, RESPECTIVELY) CONTENTS INCREASED SIGNIFICANTLY IN BOTH INTENSIVE CONTINUOUS AND INTERVAL GROUPS, HOWEVER, INTENSIVE INTERVAL TRAINING INDUCED GREATER INCREASES THAN CONTINUOUS TRAINING (P=0.02, P=0.001, P=0.001 AND P=0.001 FOR H2O2, TNF-A, BDNF AND GDNF, RESPECTIVELY).DISCUSSION: H2O2 UP-REGULATES BDNF AND GDNF EXPRESSION BY INCREASING TRANSLOCATION OF NF-KB COMPLEX FROM CYTOPLASM TO NUCLEUS AND BINDING IT TO THE TARGET SITES IN THE DNA. FURTHERMORE, IT APPEARS THAT COMPARED TO INTENSIVE CONTINUES TRAINING, INTENSIVE INTERVAL TRAINING CAN RESULT IN GREATER IMPROVEMENTS IN THE BDNF AND GDNF CONCENTRATIONS OF RAT BRAINS THROUGH FURTHER INCREASES IN H2O2 AND TNF-A. THIS MEANS THAT THE SEPARATION OF THE TRAINING SESSIONS TO VARIOUS BOUTS OF EXERCISE WITH MAXIMUM EFFORT (IN THE FORM OF INTERVAL EXERCISE) WILL LEAD TO GREATER NEUROTROPHIN GAINS.