A spin label study on the effect of dibutyryl cyclic AMP on synaptic plasma membranes isolated from rat brain

The fluidity of the deep layer of the lipid bilayer and the mobility of sulphydryl (-SH) groups of synaptic plasma membranes, isolated from rat brain and spin-labelled with a doxyl derivative of stearic acid and with a nitroxide derivative of maleimide, respectively, were studied using electron spin resonance (ESR) techniques. Dibutyryl cyclic AMP (db-cAMP) and adenosine triphosphate (ATP) had no effect on the fluidity of the deep layer of the lipid bilayer of synaptic plasma membranes. While protein dephosphorylation was inhibited by Zn2+, db-cAMP together with ATP increased the mobility of -SH groups above the value obtained with db-cAMP alone.