Developmental onset of enduring long‐term potentiation in mouse hippocampus

• Published in: Hippocampus 2020-12, Vol.30 (12), p.1298-1312
• Main Authors: Ostrovskaya, Olga I., Cao, Guan, Eroglu, Cagla, Harris, Kristen M.
• Format: Article
• Language: English
• Subjects: Animals; Animals, Newborn; development; Excitatory Postsynaptic Potentials - physiology; FMR1 protein; Genotypes; Hippocampus; Hippocampus - growth & development; Long-term potentiation; Long-Term Potentiation - physiology; Male; maturation; Mice; Mice, 129 Strain; Mice, Inbred C57BL; Mice, Knockout; Mice, Transgenic; Neuronal Plasticity - physiology; Organ Culture Techniques; Rodents; Species Specificity; Strains (organisms); Stratum radiatum; Synaptic plasticity; theta‐burst potentiation
• ISSN: 1050-9631; 1098-1063
• DOI: 10.1002/hipo.23257

Analysis of long‐term potentiation (LTP) provides a powerful window into cellular mechanisms of learning and memory. Prior work shows late LTP (L‐LTP), lasting >3 hr, occurs abruptly at postnatal day 12 (P12) in the stratum radiatum of rat hippocampal area CA1. The goal here was to determine the developmental profile of synaptic plasticity leading to L‐LTP in the mouse hippocampus. Two mouse strains and two mutations known to affect synaptic plasticity were chosen: C57BL/6J and Fmr1−/y on the C57BL/6J background, and 129SVE and Hevin−/− (Sparcl1−/−) on the 129SVE background. Like rats, hippocampal slices from all of the mice showed test pulse‐induced depression early during development that was gradually resolved with maturation by 5 weeks. All the mouse strains showed a gradual progression between P10‐P35 in the expression of short‐term potentiation (STP), lasting ≤1 hr. In the 129SVE mice, L‐LTP onset (>25% of slices) occurred by 3 weeks, reliable L‐LTP (>50% slices) was achieved by 4 weeks, and Hevin−/− advanced this profile by 1 week. In the C57BL/6J mice, L‐LTP onset occurred significantly later, over 3–4 weeks, and reliability was not achieved until 5 weeks. Although some of the Fmr1−/y mice showed L‐LTP before 3 weeks, reliable L‐LTP also was not achieved until 5 weeks. L‐LTP onset was not advanced in any of the mouse genotypes by multiple bouts of theta‐burst stimulation at 90 or 180 min intervals. These findings show important species differences in the onset of STP and L‐LTP, which occur at the same age in rats but are sequentially acquired in mice.