In utero ethanol exposure decreased the density of serotonin neurons. Maternal ipsapirone treatment exerted a...

Prior studies from this laboratory showed that in utero ethanol exposure severely retards the development of the serotonin (5-HT) system; we demonstrated a reduced concentration of 5-HT and 5-HT reuptake sites and alterations in the concentration of 5-HT(1A) receptors in ethanol-exposed offspring. These investigations also found that maternal treatment with a 5-HT(1A) agonist, buspirone, prevented most of the ethanol-associated damage to the developing 5-HT system. In the present investigation, we investigated whether the ethanol-associated changes in the 5-HT system are due to a reduction of 5-HT neurons and whether any changes in the density of 5-HT neurons can be prevented by maternal treatment with another 5-HT(1A) agonist, ipsapirone. Using immunocytochemistry, we found that in utero ethanol exposure reduced the density of 5-HT immunopositive neurons in the dorsal raphe, median raphe and B9 neurons of postnatal day 5 (PN5) rats. In all three brain areas, the offspring of ethanol-fed, saline-treated dams exhibited a 28%-40% reduction in 5-HT neurons. Ipsapirone prevented the ethanol-induced reduction in 5-HT immunopositive neurons in the dorsal raphe, median raphe and B9 neurons. In the dorsal and median raphe of control offspring, ipsapirone did not alter the concentration of 5-HT neurons. However, this drug did reduce 5-HT neurons in the B9 region of the offspring of control-fed rats.