| Abstrakt: |
At present time there is a lack of satisfactory understanding of how DHEA affects cognition and nervous system function. Aim of the present study to evaluate effects of long-term DH EA administration of physiological doses on the Higher Brain Activity (HBA) in rhesus macaques (RM) at the limits of their biological age. The study included 9 male RM aged 24-30 years. Five of them were given im injections of DHEA (1 mg/kg each two days for 3 months). 4 control monkeys were administered the vehicle alone. Cortisol, testosterone, and free thyroxin were measured by chemiluminescent immunoassay. HBA was studied by classical motor-food conditioning (to estimate long-term memory) and by determining delayed response time (a measure of short-term memory). RM had to respond to a positive signal (1000 Hz) and no bar-pressing was required in response to a negative signal (400 Hz). MR were free to move in the cage during the experiment. Their behavior was tested before, within 1, 2, 3 months of DHEA administration and 3 months after its termination. The HBA increased of all 5 RM within 1, 2, and 3 month after the beginning of DHEA administration. Both long- and short-term memory stably improved while response time decreased from 5 to 1-1.5 s. The behavior of RM changed radically from passive one to enhanced motor activity and food motivation. These effects of DHEA persisted as long as 3 months after DHEA treatment. During DHEA treatment the steady tendency to rising in a blood concentrations of a free thyroxine, testosterone and DHEA was observed. DHEA administration caused a rise in testosterone, free thyroxin levels and DHEAS levels. In three months after DHEA treatment the hairs lost in the old monkeys was restored and this effect remained within one years of observation. Conclusion. Administration of physiological doses of DHEA to old RM induced a stable increase of Higher Brain Activity with harmonization of excitation and inhibition processes; radically enhanced motor and food activity; completely restored body hairiness which already remained within one year. |
