A functional disturbance in the auditory cortex related to a low serotonergic neurotransmission in women with type 2 diabetes.
OBJECTIVE
To determine if the slope of the amplitude/stimulus intensity function (ASF) of the N1/P2 component of the auditory evoked potential was increased in women with type 2 diabetes reflecting a low brain serotonergic activity in the auditory cortex.


METHODS
In a comparative study in women with type 2 diabetes and controls, we measured free, bound and total plasma L-tryptophan (L-Trp), neutral amino acids (NAA) and free fatty acids (FFA) and recorded the N1/P2 component of the auditory evoked potential.


RESULTS
The diabetic patients were overweight and FFA and NAA in plasma were significantly elevated. The free, bound to albumin and total L-Trp were decreased. The values of free/total L-Trp and free/NAA ratios were significantly lower. The latencies of N1 and P2 at all intensities and the slope ASF of the N1/P2 component significantly increased.


CONCLUSIONS
The decrease of the free fraction of L-Trp in plasma and the increase of the ASF slope of the N1/P2 component reflect a functional relationship between the brain serotonergic activity and the N1/P2 changes in the auditory cortex, suggesting a cortical impaired activity associated with anomalies of brain serotonergic neurotransmission in women with type 2 diabetes. We proposed the ASF slope together with measurement of the plasma FFT as noninvasive clinical indicators of serotonergic neurotransmission in the brain in these as well as in other types of patients.
Manjarrez
Gabriel
G
Laboratory of Developmental Neurochemistry, Specialties Hospital, XXI Century National Medical Center (CMN SXXI), Mexican Institute of Social Security (IMSS), Mexico City, Mexico. willisga@df1.telmex.net.mx
Vazquez
Felipe
F
Delgado
Margarita
M
Herrera
Rocio
R
Hernandez
Jorge
J
D000161:Acoustic Stimulation / Q000379:methods; D001303:Auditory Cortex / Q000502:physiology*; D003924:Diabetes Mellitus, Type 2 / Q000097:blood / Q000503:physiopathology*; D005072:Evoked Potentials, Auditory / Q000502:physiology*; D005260:Female; D006801:Humans; D008875:Middle Aged; D012701:Serotonin / Q000172:deficiency / Q000378:metabolism* / Q000502:physiology; D009435:Synaptic Transmission / Q000502:physiology*
D012701:Serotonin