An exogenous source of 5-HT elevates platelet 5-HT levels in an autistic group more than in a normal group. For the simulation, the initial values of platelet 5-HT levels (ser(α, γ)) and 5-HT release rate (R) were set at zero and the system developed according to equations (1) and (2). After the system reached its steady state, an exogenous 5-HT source was "turned on" (+R
) and the system developed according to equations (24) and (25). After 5 steps, the exogenous 5-HT source was "turned off" (-R
) and the system developed according to equations (1) and (2) until it returned to its steady state. Each point is the mean of 10,000 simulated individuals whose γ had the beta distribution on the interval [0.8060, 0.9612] (see Table 1) with both shape parameters equal to 1.5 (see the text). Individual plots (not shown) looked essentially the same as the mean plots. The ratio between the autistic and normal platelet 5-HT levels (A) at step 7 (at the steady state) is 1.25 and the same ratio at step 13 is 1.35. The numerical values of the parameters were K = 0.0170, F
= 105, R
= 2000, α
= 0.1510, α
= 0.0000 (Table 1) and R
= 4000. Compare these plots with Figure 1 of Croonenberghs et al. .