Development of adenosine-dependent cyclic AMP accumulation in the avian optic tectum

The present work shows the existence of adenosine-dependent cyclic adenosine monophosphate (AMP) accumulation in the chick optic tectum. When tecta from 18-day-old embryos were incubated with the phosphodiesterase inhibitor IBMX and RO 20-1724, the cyclic AMP level increased from 39.2 to 73.3 and 285.5 pmol/mg protein, respectively. The high level obtained with RO 20-1724 could be inhibited by increasing concentrations of IBMX or by adenosine deaminase, but not by dipyridamole. 2-Chloroadenosine promoted a dose-dependent cyclic AMP accumulation in tecta incubated with RO 20-1724 and adenosine deaminase. This effect was blocked by IBMX and varied substantially during the development of the tissue. The degree of stimulation increased after day 11 of incubation, attaining maximal levels on day 14. The effect of 2-chloroadenosine remained constant until day 18, a period when both the protein content and the basal cyclic AMP levels are increasing in the developing tectum. The cyclic AMP increase elicited by 2-chloroadenosine was greatly reduced in tecta from 20-day-old embryos and 2-day-old chicks. The putative transmitters glutamate and glycine and the neurotransmitter analogs isoproterenol and carbachol had no stimulatory effect on the cyclic AMP accumulation of tecta from 10- and 17-day-old embryos.