Effect of aging and sex on the [3H]-paroxetine binding to human platelets.

Since there exist conflicting results with regard to the possible effect of aging on platelet [3H]-imipramine binding, taken as a peripheral marker of the serotonin (5-HT) transporter, we reinvestigated this matter by comparing the binding of the more selective ligand [3H]-paroxetine in 20 aged and 23 young subjects. The results showed that neither the maximum binding capacity nor the dissociation constant (Kd) were significantly different in the two groups. When the subjects were compared according to sex, the young females revealed a statistically significant lower Kd than the males, while the contrary was true for the aged females. The Kd was significantly and negatively correlated to age in males. In addition, a significant age x gender interaction was also observed. Therefore, the sex of a subject would seem to provoke significant age-related changes in the Kd of [3H]-paroxetine binding to platelet membranes. This might indicate modifications in the 5-HT transporter that could form the basis of a sex-related difference in vulnerability to disorders, such as depression, where a dysfunction at this level is hypothesized.