OCTOPAMINE-SENSITIVE ADENYLYL-CYCLASE AND G-PROTEINS IN CERATITIS-CAPITATA BRAIN DURING AGING

The loss of the ability in signalling transduction constitutes an attr active hypothesis to explain the age-related loss of functions in the nervous system. In this paper we have examined adenylyl cyclase and G proteins in Ceratitis capitata brain during aging. The intermediate le vel of complexity of the Mediterranean fruit fly and its short lifespa n make it a particularly interesting system for aging studies. Adenyly l cyclase basal activity decreased in the course of aging. By contrast , neither guanine nucleotide-induced activation of adenylyl cyclase no r Gs protein levels were modified. However, adenylyl cyclase activatio n by octopamine, which is a major neurotransmitter, neuromodulator and neurohormone in insects, was lost during aging. This observation corr elated with a decrease in octopamine binding to brain plasma membranes that was due to a decrease in both receptor affinity and binding site s. On the other hand, we observed an increase in the expression of C. capitata Go protein with age, as revealed by pertussis toxin-catalysed ADP-ribosylation and immunoblotting experiments, that was not correla ted with an increase in beta subunit levels. This report constitutes t he first direct evidence for the participation of a Go protein in agin g in the nervous system.