title: Co-induction of long-term potentiation and long-term depression at a central synapse in the leech.
abstract: Most studies of long-term potentiation (LTP) have focused on potentiation induced by the activation of postsynaptic NMDA receptors (NMDARs). However, it is now apparent that NMDAR-dependent signaling processes are not the only form of LTP operating in the brain [Malenka, R. C., & Bear, M. F. (2004). LTP and LTD: An embarrassment of riches. Neuron, 44, 5-21]. Previously, we have observed that LTP in leech central synapses made by the touch mechanosensory neurons onto the S interneuron was NMDAR-independent [Burrell, B. D., & Sahley, C. L. (2004). Multiple forms of long-term potentiation and long-term depression converge on a single interneuron in the leech CNS. Journal of Neuroscience, 24, 4011-4019]. Here we examine the cellular mechanisms mediating T-to-S (T-->S) LTP and find that its induction requires activation of metabotropic glutamate receptors (mGluRs), voltage-dependent Ca(2+) channels (VDCCs) and protein kinase C (PKC). Surprisingly, whenever LTP was pharmacologically inhibited, long-term depression (LTD) was observed at the tetanized synapse, indicating that LTP and LTD were activated at the same time in the same synaptic pathway. This co-induction of LTP and LTD likely plays an important role in activity-dependent regulation of synaptic transmission.
authors.affiliation: Neuroscience Group, Division of Basic Biomedical Sciences, Sanford School of Medicine, University of South Dakota, 414 E. Clark St., Vermillion, SD 57069, USA. bburrell@usd.edu
authors.forename: Brian D
authors.initials: BD
authors.lastname: Burrell
authors.forename: Qin
authors.initials: Q
authors.lastname: Li
mesh_terms: D000818:Animals; D015220:Calcium Channels / Q000502:physiology; D017952:Ganglia, Invertebrate / Q000166:cytology* / Q000502:physiology*; D047709:Hirudo medicinalis; D007395:Interneurons / Q000502:physiology; D017774:Long-Term Potentiation / Q000502:physiology*; D036881:Long-Term Synaptic Depression / Q000502:physiology*; D008465:Mechanoreceptors / Q000502:physiology; D023421:Models, Animal; D009473:Neuronal Plasticity / Q000502:physiology; D011493:Protein Kinase C / Q000502:physiology; D018094:Receptors, Metabotropic Glutamate / Q000502:physiology; D009435:Synaptic Transmission / Q000502:physiology*
chemical_list: D015220:Calcium Channels; D018094:Receptors, Metabotropic Glutamate; D011493:Protein Kinase C