Research reportPostnatal development changes in excitatory synaptic activity in the rat locus coeruleus neurons

- A feature of synaptic maturation is an activity-dependent switch in the NMDA EPSC decay from slow to fast.
- Glutamatergic synapses show NMDA receptor activity from the first postnatal week.
- The kinetics of AMPA receptors matures early, whereas developmental changes in NMDA receptor kinetics proceed more gradually.
- Rise time kinetics of NMDA-mediated currents appears to mature earlier than decay kinetics.

Glutamatergic synapses are shown to mature during activity and development. In order to further explore how glutamate can change the excitability of noradrenergic neurons of locus coeruleus (LC) and to better understand the involvement of Amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) and N-methyl-d-aspartate (NMDA) receptors complements across the LC, we investigated developmental changes in their activity during first postnatal weeks.Spontaneous and evoked excitatory postsynaptic currents (sEPSC and eEPSCs) were recorded in neurons of LC slices from 7, 14 and 21 days old rats using the whole cell patch clamp method. Also, the AMPA/NMDA current ratio (A/N) was measured.A pronounced AMPAR and NMDAR components mediated involvement in synaptic transmission were seen from the first postnatal week. Over this period of development, we have demonstrated that AMPA sEPSCs show an increase in frequency without major changes in their amplitude, while NMDA sEPSCs show an increase in frequency with a major change in amplitude. Neither the probability of release nor the AMPA/NMDA ratio was found to change significantly with age.It is concluded that NMDAR activity as well as AMPAR activity may be involved in coerulear excitability and modulatory effect during postnatal development.