Fig. 1.

5-HT promotes the development of neurons in vitro, and this effect is blocked by methysergide. Intestinal cells (E16) were dissociated and cultured in the presence of vehicle (control) or the indicated experimental compounds for 48 hr. The concentration of methysergide was 10 μm. All of the neurons (PGP9.5-immunoreactive cells) on each cultured dish were counted. Data are presented as the actual number of neurons found in each dish. The total number of cells per culture does not differ significantly between conditions.