Mutually independent cyclic AMP and sodium responses to nerve growth factor in embryonic chick dorsal root ganglia.

Abstract

Abstract: Chick embryo dorsal root ganglia display a rapid and transient rise in their cyclic AMP content when presented with nerve growth factor. These ganglia also depend on nerve growth factor for control of their intracellular Na+ and K+ levels. A sequential relationship between the cyclic AMP and Na+ responses is not readily apparent. Incubation of chick sensory ganglia in a sodium‐free medium does not prevent the cyclic AMP response to nerve growth factor from occurring. When ganglia are first incubated with ouabain for 6 h, presentation of nerve growth factor elicits a cyclic AMP response, but no Na+ response. The cyclic AMP response therefore does not depend on the Na+ environment. An initial presentation of nerve growth factor to the ganglia for 30 min, followed by its withdrawal and subsequent re‐administration at different intervals over several hours failed to result in a second cyclic AMP response. Nevertheless, the expected Na+ behaviors were still observed. Dibutyryl cyclic AMP is capable of eliciting a cyclic AMP response in chick sensory ganglia after 6 h of nerve growth factor deprivation. When both agents were presented simultaneously to the ganglia, only a single cyclic AMP response was obtained, corresponding in time to the response elicited by dibutyryl cyclic AMP alone‐indicating that this drug acts on the NGF‐sensitive cells. At the same time dibutyryl cyclic AMP alone failed to result in a Na+ response, leading one to conclude that the cyclic AMP response to nerve growth factor is truly not mediating the Na+ response. Additional support for the mutual independence of these two short‐latency responses is provided by the apparent inability of nerve growth factor to cause a cyclic AMP response in chick embryo sympathetic ganglia, another traditional target for the factor, which is capable of displaying a Na+ response.