Opposite morphological responses of partially denervated cortical serotonergic and noradrenergic axons to repeated stress in adult rats.
We examined plastic changes in serotonin (5-HT) axons following repeated stress in the adult rat brain, and compared stress-induced changes between 5-HT and noradrenaline (NA) axons. We locally injected the specific neurotoxin to 5-HT axons or to NA axons into the frontal cortex to cause partial denervation. The animals were mildly restrained from 1 day after the neurotoxin injection and this stress was repeated daily for 20 min during the first 2 days and for 40 min during the next 11 days. On the fourteenth day after injection, the brains were removed to visualize 5-HT and NA axons by immunohistochemistry. Repeated stress did not significantly alter the denervation area of 5-HT or NA axons, but the density of 5-HT axons was increased whereas that of NA axons was decreased in cortical regions outside the denervation site. In addition, the expression of brain-derived neurotrophic factor (BDNF) was increased in cortical regions where the 5-HT axon density was increased in response to stress. These results suggest that repeated stress causes opposite changes in the morphology of partially denervated 5-HT and NA axons in the cerebral cortex. The stress-induced increase in BDNF expression may contribute to 5-HT axon sprouting following repeated stress.
Liu
Y
Y
Department of Neuroscience, Yamaguchi University School of Medicine, Ube, Yamaguchi 755-8505, Japan.
Ishida
Y
Y
Shinoda
K
K
Furukawa
S
S
Nakamura
S
S
D015115:5,6-Dihydroxytryptamine / Q000633:toxicity; D000818:Animals; D001369:Axons / Q000378:metabolism / Q000473:pathology*; D019208:Brain-Derived Neurotrophic Factor / Q000378:metabolism; D002452:Cell Count; D002540:Cerebral Cortex / Q000378:metabolism / Q000473:pathology*; D003714:Denervation; D004299:Dopamine beta-Hydroxylase / Q000378:metabolism; D007839:Functional Laterality / Q000502:physiology; D007150:Immunohistochemistry / Q000379:methods; D008297:Male; D009498:Neurotoxins / Q000633:toxicity; D009638:Norepinephrine / Q000378:metabolism*; D016627:Oxidopamine / Q000633:toxicity; D051381:Rats; D017207:Rats, Sprague-Dawley; D012701:Serotonin / Q000378:metabolism*; D013238:Stereotaxic Techniques; D013312:Stress, Physiological / Q000473:pathology*
D019208:Brain-Derived Neurotrophic Factor; D009498:Neurotoxins; D012701:Serotonin; D016627:Oxidopamine; D004299:Dopamine beta-Hydroxylase; D015115:5,6-Dihydroxytryptamine; D009638:Norepinephrine