A significant negative correlation was observed between 5-HT1A receptor binding potential in the hippocampus and the verbal and general memory indices of WMS-R (25, 26) (t1 and F1). No significant correlations were observed among any other indices and regions, and there was no age effect on binding potential in any region. The significance of this correlation was consistent with the finding from the analysis using statistical parametric mapping (31), which revealed significant correlation in the bilateral hippocampus (Montreal Neurological Institute coordinates: x=–30, y=–22, z=–14 in the left side; x=34, y=–28, z=–12 and x=40, y=–4, z=–28 in the right side) (F2).
As seen in t2, the effect of the stimulation of 5-HT1A receptors with tandospirone on explicit memory function, as measured with the Auditory Verbal Learning Test (33), revealed a significant dose-dependent decline in performance (immediate recall: F=7.33, df=2, 16, p=0.005; postinterference recall: F=4.47, df=2, 16, p<0.03; delayed recognition: F=3.65, df=2, 16, p=0.05). Post hoc analysis revealed that the placebo condition differed significantly from the 60-mg tandospirone condition in immediate recall (t=12.3, df=16, p=0.003), postinterference recall (t=2.22, df=16, p<0.04), and delayed recognition (t=0.67, df=16, p<0.05). On the other hand, there was no significant drug effect on the performance of the word fluency task (initial word fluency: F=2.31, df=2, 16, p=0.13; category word fluency: F=2.22, df=2, 16, p=0.14), digit span (forward: F=0.17, df=2, 16, p=0.85; backward: F=0.26, df=2, 16, p=0.77) or the Stroop task (F=1.37, df=2, 16, p=0.28).
Neuroendocrinological examinations revealed that tandospirone dose-dependently decreased body temperature (F=17.84, df=2, 16, p=0.008) and increased GH (F=12.04, df=1.1, 8.7, p=0.007). Post hoc analysis revealed that the placebo condition differed significantly from the 30- and 60-mg tandospirone conditions regarding change in body temperature (30 mg: t=0.16, df=16, p<0.04; 60 mg: t=0.33, df=16, p=0.0001) and from the 60-mg condition for GH (t=9.0, df=16, p=0.001). The changes in mean outcome parameters of memory function paralleled those of body temperature and GH (t2 and F3), although there were no statistically significant correlations among these measures because of their large interindividual variabilities, as indicated by the standard deviations.