Accumulation of cyclic adenosine monophosphate (cAMP) elicited by adenosine was studied in slices and membrane preparations of optic tectum from chicks aged 1-13 days post-hatch. Accumulation of cAMP promoted by adenosine declined with age, the highest value being observed in three-day-old chicks and the lowest in 11-day-old chicks. However, when the slices were incubated with adenosine and the phosphodiesterase inhibitor-Ro 20-1724 the differences between the two ages were abolished, suggesting a higher phosphodiesterase activity in 11-day-old chicks. In membrane preparations, although basal adenylate cyclase activity was lower in three-day-old chicks, the guanylyl-imidodiphosphate (Gpp(NH)p) concentration curves for stimulation of adenylate cyclase activity indicated a higher sensitivity of G protein to Gpp(NH)p at this age. This hypothesis was reinforced by the observation that the binding of [3H]Gpp(NH)p to the membrane preparation was greater in three-day-old animals. In spite of these differences, the percentage of adenylate cyclase activity stimulation by 2-chloroadenosine (2CADO)+Gpp(NH)p was the same at both ages. These findings suggest that the decreased response evoked by adenosine during development is probably due to increased phosphodiesterase activity and a lower sensitivity of adenylate cyclase activity to Gpp(NH)p.