Chronic exposure to caffeine during early development increases dendritic spine and branch formation in midbrain...

Sibling juvenile jewel fish were chronically exposed to caffeine solution (14 mg/l) between 50 and 100 days after fertilization. Some experimental animals were sacrificed at this time, together with control siblings reared without drugs; others were allowed to recover in the absence of caffeine for 18 months. Golgi-stained preparations showed increased formation of dendritic spines on apical stem dendrites of pyriform tectal neurons in juveniles exposed to caffeine. Adults showed minimal effects on the stem dendrite, but caffeine adults formed more primary dendritic branches and more spines on branches than controls did. This study demonstrates the facilitation of neuronal growth and complexity by chronic administration of a chemical agent commonly present during early development in humans.