[Changes in cerebra serotonin synthesis induced by insulin-dependent diabetes mellitus].
OBJECTIVE
Evaluate if the rats with diabetes mellitus insulin-dependent have a minor activity of the serotonergic biosynthetic pathway through the decrease of the free fraction of L-tryptophan in plasma.


METHODS
Diabetes mellitus was induced in rats, and the brain serotonergic biosynthetic activity was evaluated at 7, 14, and 21 days after streptozotocin administration.


RESULTS
The diabetic animals showed a general decrease in body weight. In plasma they had a decrease in the free fraction of L-tryptophan. Also, in the brain they show low levels of the amino acid, as well as decrease of the activity of the limiting enzyme tryptophan-5-hydroxylase and its product serotonin. Interestingly, the activity of the enzyme was higher in the brainstem from day 14, accompanied with an elevation of the neurotransmitter.


CONCLUSIONS
The results confirm that diabetes mellitus insulin-depend induce chronic undernourishment. The low levels of L-tryptophan in blood of the diabetic animals suggest a minor transport of the amino acid to the brain and a decrease in serotonin synthesis, in cerebral cortex and hypothalamus. Besides, during the evolution of the disease, the activity of tryptophan hydroxylase was elevated, independently of L-tryptophan concentration in the brainstem of diabetic animals, suggesting a different response according to the brain region and possibly a different functional change, accompanied by an increase in the synthesis of the neurotransmitter.
Manjarrez-Gutiérrez
G
G
Laboratorio de Neuroquímica del Desarrollo, Hospital de Especialidades, Centro Médico Nacional Siglo XXI (CMN), Instituto Mexicano del Seguro Social (IMSS), México, D.F. México.
Herrera-Márquez
J R
JR
Molina-Hernández
A
A
Bueno-Santoyo
S
S
González-Ramírez
M
M
Hernández
J
J
D000818:Animals; D001921:Brain / Q000378:metabolism*; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism*; D003922:Diabetes Mellitus, Type 1 / Q000378:metabolism*; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D012701:Serotonin / Q000096:biosynthesis*
D012701:Serotonin