Comparison of pharmacological agents (aspartate vs. aminophosphonobutyric plus kynurenic acids) to block synaptic transmission from retinal photoreceptors in frog.
The combination of aminophosphonobutyric plus kynurenic acids (APB/Kyn) was compared to aspartate with respect to its ability to block synaptic transmission from photoreceptors. Like aspartate, APB/Kyn blocks photoreceptor synaptic transmission, as monitored by the b- and d-waves of the electroretinogram, by the proximal negative response and M-wave of the proximal retina, and by the light-evoked increase in extracellular K+ concentration in the inner plexiform layer. Unlike aspartate, APB/Kyn has relatively minor effects on retinal resistance, light-evoked changes in K+ and Ca2+ concentrations in the subretinal space, light-evoked changes in subretinal space volume, resting extracellular concentrations of K+ and Ca2+ in the proximal and distal retina, and the c-wave. Effects of APB/Kyn are generally more reversible than effects of Asp. A disadvantage of APB/Kyn is that the a-wave usually becomes smaller and slower. Overall, APB/Kyn disrupts the retina less than aspartate. Therefore, in some situations in which blockade of photoreceptor synaptic transmission is desired, the use of APB/Kyn may be preferable to that of aspartate.
Xu
X J
XJ
Department of Psychology, University of Georgia, Athens 30602.
Xu
J
J
Huang
B
B
Livsey
C T
CT
Karwoski
C J
CJ
D000613:Aminobutyrates / Q000494:pharmacology*; D000818:Animals; D001224:Aspartic Acid / Q000494:pharmacology*; D003864:Depression, Chemical; D004596:Electroretinography / Q000187:drug effects; D007736:Kynurenic Acid / Q000494:pharmacology*; D010786:Photoreceptor Cells / Q000187:drug effects*; D011894:Rana pipiens; D012160:Retina / Q000187:drug effects*; D009435:Synaptic Transmission / Q000187:drug effects*
D000613:Aminobutyrates; D001224:Aspartic Acid; D007736:Kynurenic Acid; C012729:2-amino-4-phosphonobutyric acid