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Ontogeny of synaptic transmission in the rat hippocampus
I E Kudryashov1, I V Kudryashova
1Institute of Higher Nervous Activity and Neurophysiology, Russian Academy of Science, 5a Butlerov str., 117485, Moscow, Russia. neuroont@msk.ru
Insights
This study reveals that population spike amplitude in juvenile rat hippocampi shows dynamic maturation, with a notable decrease between days 19-22, potentially linked to behavioral development.
Area of Science:
- Neuroscience
- Developmental Neuroscience
- Electrophysiology
Background:
- The maturation of hippocampal circuitry is crucial for cognitive functions.
- Understanding the electrophysiological development in juvenile rodents provides insights into neural plasticity.
Purpose of the Study:
- To compare the electrophysiological characteristics of hippocampal slices from juvenile and young Wistar rats.
- To investigate the ontogeny of excitatory processes and population spike maturation in the developing hippocampus.
Main Methods:
- Electrophysiological recordings were performed on hippocampal slices from Wistar rats aged postnatal day (PN) 14 to PN27.
- Input-output curves were utilized to quantify excitatory processes and population spike (PS) amplitude dynamics.
- Measurements were taken daily during the juvenile period to capture fine-grained developmental changes.
Main Results:
- Population spike (PS) maturation was uneven, exhibiting a transient decrease in amplitude from PN19 to PN22.
- Input-output curves showed age-dependent differences, with younger animals generally reaching PS saturation at lower stimulus intensities.
- Slices from 19-day-old rats did not display saturated input-output curves within the tested stimulus range (2-20 V).
Conclusions:
- The dynamic changes in hippocampal PS amplitude during early ontogeny, including the observed depression, correlate with the emergence of specific behaviors.
- This suggests a potential functional relevance of hippocampal population spike amplitude depression during critical developmental periods.
Abstract:
Electrophysiological characteristics of the hippocampal slices of juvenile (14-27 days) or young (36-40 days) Wistar rats have been compared. In the juvenile rats measurements were taken daily, from postnatal day (PN) 14 to PN27. Input-output curves were used to quantify the ontogeny of excitatory processes. The dynamic of population spike (PS) maturation was not even during the investigated postnatal period. After day 19 transient decrease of PS amplitude was observed until day 22. There were also some differences between the shape of input-output curves from the slices of rats of different ages. In general, PS was saturated at lower intensities in younger animals. The slices from 19-day-old rats did not display saturated input-output curve with 2-20 V stimuli intensities. But input-output curves on PN20-22 were rather similar to that obtained before PN19. The periods of gradual increase and subsequent decrease of PS amplitudes during early ontogeny correlate with the appearance of certain forms of behaviour. This fact suggests that hippocampal PS amplitude depression may be relevant functionally.