The C. elegans Glutamate Receptor Subunit NMR-1 Is Required for Slow NMDA-Activated Currents that Regulate Reversal Frequency during Locomotion

Penelope J. Brockie, Jerry E. Mellem, Thomas Hills, David M. Madsen, Andres V. Maricq
2001 Neuron  
with spatial learning (Tsien et al., 1996) , whereas overexpression of the NMDA receptor subunit NR2B increases LTP and performance in behavioral tasks (Tang et al., 1999) . A second characteristic that distinguishes NMDA receptors from the non-NMDA subtypes is their slow kinet-Salt Lake City, Utah 84112 ics. Thus, activation of NMDA receptors results in longlived currents that may promote rhythmic activity, such as in spinal cord neurons that control locomotion in Summary lamprey (Sigvardt et
more » ... l., 1985), amphibia (Sillar and Simmers, 1994) , and mammals (Schmidt et al., 1998). The The N-methyl-D-aspartate (NMDA) subtype of glutatime course of currents mediated by NMDA receptors mate receptor is important for synaptic plasticity and may also facilitate spatiotemporal integration of sensory nervous system development and function. We have inputs (Viana Di Prisco et al., 1995) . In particular, one used genetic and electrophysiological methods to role for NMDA receptors in the retina depends on its demonstrate that NMR-1, a Caenorhabditis elegans slow rate of desensitization. By providing a maintained NMDA-type ionotropic glutamate receptor subunit, current response to glutamate that acts in concert with plays a role in the control of movement and foraging the rapidly desensitizing currents mediated by nonbehavior. nmr-1 mutants show a lower probability of NMDA receptors, NMDA receptors participate in the switching from forward to backward movement and synaptic transfer of graded photoresponses from bipoa reduced ability to navigate a complex environment. lar to ganglion cells (Matsui et al., 1998; Taylor et al., Electrical recordings from the interneuron AVA show 1995). that NMDA-dependent currents are selectively dis- A large variety of NMDA receptor subtypes, each with rupted in nmr-1 mutants. We also show that a slowly distinguishing features, participates in neural circuits desensitizing variant of a non-NMDA receptor can resthroughout the central nervous system. Because pharcue the nmr-1 mutant phenotype. We propose that macological tools are likely to target a variety of NMDA NMDA receptors in C. elegans provide long-lived curreceptor subtypes, it is difficult to address how a particrents that modulate the frequency of movement reverular NMDA receptor subunit contributes to the function sals during foraging behavior. of a specific neural circuit. To address this question, we have undertaken a genetic and electrophysiological
doi:10.1016/s0896-6273(01)00394-4 pmid:11545720 fatcat:xrdg45gybrflphy67wya3jeiyi