An in vitro study of long-term potentiation in the carp (Cyprinus carpio L.) olfactory bulb
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Long-term potentiation (LTP) of synaptic transmission is considered a cellular mechanism for neural plasticity and memory formation. Previously, we showed that in the carp olfactory bulb, LTP occurs at the dendrodendritic mitral-to-granule cell synapse following tetanic electrical stimulation applied to the olfactory tract, and suggested that it is involved in the process of olfactory memory formation. As a first step towards understanding mechanisms underlying plasticity at this synapse, we examined the effects of various drugs (glutamate and GABA receptor agonists and antagonists, noradrenaline, and drugs affecting cAMP signaling) on dendrodendritic mitral-to-granule cell synaptic transmission in an in vitro preparation. Two forms of LTP are involved: a postsynaptic form (tetanus-evoked LTP) and a presynaptic form. The postsynaptic form is evoked at the granule cell dendrite following tetanic olfactory tract stimulation and is suppressed by the NMDA receptor antagonist, D-AP5, enhanced by noradrenaline, and occluded by the metabotropic glutamate receptor agonist, trans-ACPD. The presynaptic form occurs at the mitral cell dendrite following blockade of the GABAA receptor by picrotoxin and bicuculline, or via activation of cAMP signaling by forskolin and 8-Br-cAMP.
KeywordsLong-term potentiation Dendrodendritic mitral-to-granule cell synapse Olfactory bulb Carp In vitro preparation
Artificial cerebrospinal fluid
8-Bromoadenosine 3′,5′-cyclic monophosphate
Component 2 wave
Ionotropic glutamate receptor
Metabotropic glutamate receptor
This work was supported by grants from the Ministry of Education, Culture, Sports, Science and Technology of Japan and from the Ministry of Agriculture, Forestry and Fisheries of Japan. All experiments comply with the Animal Care and Use Committee guidelines of Yokohama City University and with the regulations for the care and use of laboratory animals in Japan.
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