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Serotonergic modulation of synapses in the developing gerbil lateral superior olive
1Center for Neural Science, New York University, New York City, New York 10003, USA.
Journal of Neurophysiology
|June 16, 1999
Summary
Serotonin (5-HT) significantly impacts auditory circuit development in gerbils by modulating synaptic function in the lateral superior olive (LSO). This neuromodulator influences inhibitory and excitatory postsynaptic currents, potentially shaping auditory processing and plasticity.
Area of Science:
- Neuroscience
- Auditory System Development
- Synaptic Plasticity
Background:
- The lateral superior olive (LSO) is crucial for binaural hearing, integrating auditory inputs to process interaural level differences (ILDs).
- LSO circuit maturation during early postnatal development is activity-dependent, suggesting neuromodulators play a role.
- Serotonin (5-HT) is a key neuromodulator with known effects on neuronal excitability and synaptic transmission.
Purpose of the Study:
- To investigate the effects of serotonin (5-HT) on synaptic function in the developing gerbil LSO.
- To characterize the distinct forms of serotonergic modulation on spontaneous and evoked synaptic currents.
- To identify the specific serotonin receptor subtypes involved in these modulatory effects.
Main Methods:
- Whole-cell voltage-clamp recordings were performed on gerbil LSO neurons (postnatal days 6-13) in an in vitro slice preparation.
- Application of 5-HT and specific 5-HT receptor agonists/antagonists were used to assess effects on synaptic transmission.
- Tetrodotoxin was used to confirm the origin of 5-HT-induced spontaneous inhibitory postsynaptic currents (IPSCs).
Main Results:
- 5-HT (100 microM) induced prolonged bursts of spontaneous IPSCs, an effect primarily observed in younger animals (postnatal days 6-8).
- 5-HT profoundly depressed evoked excitatory postsynaptic currents (EPSCs) and, to a lesser extent, evoked IPSCs.
- 5-HT2 receptor activation mimicked all observed effects, while 5-HT1 receptor activation contributed to EPSC depression, indicating distinct receptor-mediated mechanisms.
Conclusions:
- Serotonin significantly modulates synaptic transmission in the developing LSO through distinct receptor pathways.
- The induction of spontaneous IPSCs by 5-HT in young animals suggests a role in developmental plasticity of inhibitory synapses.
- The preferential depression of EPSCs by 5-HT may contribute to the refinement of ILD tuning in the mature auditory system.