Ionic dependence of membrane potential and glutamate receptor-linked responses in synaptoneurosomes as measured with a cyanine dye, DiS-C2-(5).
Membrane potentials of particles present in a subcellular brain preparation, called synaptoneurosomes, have been monitored by measurement of changes in the absorbance of a cyanine dye, DiS-C2-5. The membrane potential of the particles seems to be dependent on both Cl- and K+ diffusion potentials, as judged from dependence of the absorbance changes on the K+ equilibrium potential across the membrane in the presence of Ba2+ or when Cl- was replaced with gluconate. The apparent high Cl- permeability of the membrane preparation was reduced in the presence of picrotoxin, a finding suggesting endogenous activation of receptor-linked Cl- channels. Glutamate and kainate caused depolarization of the membranes present in the preparation. This effect was only seen if K+ channels had been blocked in the presence of Ba2+ or 4-aminopyridine. No responses were observed with other glutamate receptor agonists (quisqualate or N-methyl-D-aspartate). The membrane potential of particles present in conventional synaptosomal preparations neither had a high Cl- permeability nor reacted to glutamate or kainate in the present conditions. The results suggest that synaptoneurosome preparations may be used for functional studies on postsynaptic neurotransmitter receptor-linked membrane potential changes with optical probes of membrane potential.
D000818:Animals; D052160:Benzothiazoles; D002232:Carbocyanines; D006096:Gramicidin / Q000494:pharmacology; D008564:Membrane Potentials; D010852:Picrotoxin / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D011804:Quinolines; D011813:Quinuclidinyl Benzilate / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D017470:Receptors, Glutamate; D017981:Receptors, Neurotransmitter / Q000378:metabolism*; D013569:Synapses / Q000166:cytology* / Q000378:metabolism; D013844:Thiazoles; D014634:Valinomycin / Q000494:pharmacology
D052160:Benzothiazoles; D002232:Carbocyanines; D006096:Gramicidin; D010852:Picrotoxin; D011188:Potassium; D011804:Quinolines; D011813:Quinuclidinyl Benzilate; D017470:Receptors, Glutamate; D017981:Receptors, Neurotransmitter; D013844:Thiazoles; D014634:Valinomycin; C025905:3,3'-diethylthiatricarbocyanine