Spinal Cord Hemisection Facilitates Aromatic L-Amino Acid Decarboxylase Cells to Produce Serotonin in the Subchronic but Not the Chronic Phase.
Neuromodulators, such as serotonin (5-hydroxytryptamine, 5-HT) and noradrenalin, play an essential role in regulating the motor and sensory functions in the spinal cord. We have previously shown that in the rat spinal cord the activity of aromatic L-amino acid decarboxylase (AADC) cells to produce 5-HT from its precursor (5-hydroxytryptophan, 5-HTP) is dramatically increased following complete spinal cord transection. In this study, we investigated whether a partial loss of 5-HT innervation could similarly increase AADC activity. Adult rats with spinal cord hemisected at thoracic level (T11/T12) were used with a postoperation interval at 5 days or 60 days. Using immunohistochemistry, first, we observed a significant reduction in the density of 5-HT-immunoreactive fibers in the spinal cord below the lesion on the injured side for both groups. Second, we found that the AADC cells were similarly expressed on both injured and uninjured sides in both groups. Third, increased production of 5-HT in AADC cells following 5-HTP was seen in 5-day but not in 60-day postinjury group. These results suggest that plastic changes of the 5-HT system might happen primarily in the subchronic phase and for longer period its function could be compensated by plastic changes of other intrinsic and/or supraspinal modulation systems.
Department of Neuroscience and Pharmacology, University of Copenhagen, 2200 Copenhagen, Denmark.
Bushra
B
Azam
Department of Neuroscience and Pharmacology, University of Copenhagen, 2200 Copenhagen, Denmark ; Department of Nutrition, Exercise and Sports, University of Copenhagen, 2200 Copenhagen, Denmark.
Jacob
J
Wienecke
Department of Nutrition, Exercise and Sports, University of Copenhagen, 2200 Copenhagen, Denmark.
Dennis Bo
DB
Jensen
Department of Neuroscience and Pharmacology, University of Copenhagen, 2200 Copenhagen, Denmark.
Aleena
A
Azam
Department of Neuroscience and Pharmacology, University of Copenhagen, 2200 Copenhagen, Denmark ; Department of Experimental Science, Neuronano Research Center, Lund University, 223 81 Lund, Sweden.
Mengliang
M
Zhang
D006916:5-Hydroxytryptophan / Q000494:pharmacology; D000818:Animals; D001142:Aromatic-L-Amino-Acid Decarboxylases / Q000378:metabolism*; D002230:Carbidopa / Q000494:pharmacology; D002908:Chronic Disease; D006614:Hindlimb / Q000503:physiopathology; D008297:Male; D009412:Nerve Fibers / Q000378:metabolism; D009473:Neuronal Plasticity; D009474:Neurons / Q000201:enzymology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012701:Serotonin / Q000096:biosynthesis*; D013119:Spinal Cord Injuries / Q000201:enzymology / Q000378:metabolism* / Q000503:physiopathology; D013623:Tail / Q000503:physiopathology; D013904:Thoracic Vertebrae
D012701:Serotonin; D006916:5-Hydroxytryptophan; D001142:Aromatic-L-Amino-Acid Decarboxylases; D002230:Carbidopa