Effects of Local Anesthetics on Rotational Mobility of n- (9-Anthroyloxy) stearic Acid in Neuronal Membranes

To elucidate the molecular mechanism of pharmacological action of local anesthetics, we studied membrane actions of tetracaine, bupivacaine, lidocaine, prilocaine and procaine. Fluorescence polarization of n- (9-anthroyloxy) stearic acid (n-AS) was used to examine the effects of these local anesthetics on differential rotational mobility of different positions of the number of synaptosomal plasma membrane vesicle (SPMV) phospholipid carbon atoms. The four membrane components differed with respect to 3, 6, 9 and 16- (9-anthroyloxy) stearic acid (3-AS, 6-AS, 9-AS and 16-AP) probes, indicating that differences in the membrane fluidity might be present. Degrees of the rotational mobility of 3-AS, 6-AS, 9-AS and 16-AP were different depending on depth of hydrocarbon interior. In a dose-dependent manner, tetracaine, bupivacaine, lidocaine, prilocaine and procaine decreased anisotropy of 3-AS, 6-AS, 9-AS and 16-AP in the hydrocarbon interior of the SPMV. These results indicate that local anesthetics have significant disordering effects on hydrocarbon interior of the SPMV, thus affecting the transport of Na+ and K+ in nerve membranes and leading to anesthetic action.

Different effects of dopamine on differential rotational mobility between inner and outer monolayer of synaptosomal plasma membrane vesicles isolated from bovine brain

Fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene (DPH) was used to evaluate the effects of dopamine cntdot HCl on the range of the rotatioanl mobility of bulk bilayer structure of the synaptosomal plasma membrane vesicles (SPMV) isolated from whole bovine brain. In a dose-dependent manner, dopamine decreased the anisotropy (gamma), limiting anisotropy (gammainfin) and order parameter (S) of DPH in the membranes. These indicate that dopamine increased the rotational mobility of the probe in the neuronal membranes. Cationic 1-(4-(trimethylammonio)-phenyl)-6-phenylhexa-1,3,5-hexatriene (TMA-DPH) and anionic 3-(p-(6-phenyl)-1,3,5-hexatrienyl)-phenylpropionic acid (PRO-DPH) were utilized to examine the range of transbilayer asymmetric rotational mobility of the neuronal membranes. Dopamine had a greater increasing effect on the mobility of the inner monolayer as compared to the outer monolayer of the neuronal membranes. It has been proven that dopamine exhibits a selective rather than nonselective fluidizing effect within the transbilayer domains of the SPMV.