Meeting Abstract
P1.136 Sunday, Jan. 4 Pre- & Post-synaptic Actions of Kainate: Negative Feedback at Glutamatergic Nerve Terminals LEE, J.-Y.*; BHATT, D; BHATT, D; CHUNG, W.-Y.; COOPER, R.L.; Dept of Biology, Univ of KY, Lexington, KY, & Army, Daejun, Republic of Korea; Univ of KY; Univ of KY; Dept. of Chem, Korea Military Academy, Seoul, Republic of Korea; Univ of KY c14586@gmail.com
Drosophila larval neuromuscular junctions (NMJs) serve as a model for various gene mutations of synaptically relevant molecules to characterize synaptic physiology. The molecular sequence of the glutamate receptors have been described; however, the pharmacological profile of glutamate receptor subtypes at the NMJ have not been fully elucidated. We present evidence for self regulation (i.e. negative auto-feedback) at the NMJ in Drosophila. Based on the pharmacological profile these presynaptic autoreceptors are likely a kainate subtype of glutamate receptors. Kainate does not depolarize the muscle, but evoked EPSP dampen when kainate is present and mini frequency is reduced. Quantal responses show a decreased amplitude and area under the voltage curve indicative of reduced postsynaptic receptor sensitivity to glutamate transmission. ATPA, a kainate receptor agonist, mimics kainate action both pre- and post-synaptically. Domoic acid, a quisqualate receptor antagonist, blocks the postsynaptic receptors without depolarizing the muscle, which supports earlier findings of the muscle containing quisqualate subtype receptors. No effects are seen on the frequency of spontaneous events in low concentration of domoic acid which causes a 50% reduction in quantal amplitude. The results suggest a kainate pre-synaptic auto-inhibitory feedback on evoked release. The mechanism of action within the presynaptic terminal remains to be elucidated. The mild direct postsynaptic action of kainate is likely due to partial antagonist action on the quisqualate receptors. Funding:NSF-IBN-0131459 (RLC), Univ. KY (JYL), Korean Army & Korea Military Academy (JYL, WYC).
