It is well known that young organisms do not maintain memories as long as adults, but the mechanisms for this ontogenetic diﬀerence are undetermined. Previous work has revealed that the α-amino-3-hydroxy-5-methyl-4isoxazolepropionic acidreceptor (AMPAr)subunits aretraﬃckedinto the synaptic membranefollowing memory retrieval in adults. Additionally, phosphorylated PSD-95-pS295 promotes AMPAr stabilization at the synapse. We investigated these plasticity related proteins as potential mediators in the diﬀerential contextual stress memory retrieval capabilities observed between adult and juvenile rats. Rats were assigned to either pedestal stress (1h) or no stress control (home cage). Each animal was placed alone in an open ﬁeld for 5minat the base of a 6×6 sq inch pedestal (4ft high). Stress subjects were then placed on this pedestal for 1hr and control subjects were placed in their homecage following initial exploration. Each animal was returned to the open ﬁeld for 5min either 1d or 7d following initial exposure. Freezing postures were quantiﬁed during the memory retrieval test. The 1d test shows adult (P90) and juvenile (P26) stressed rats increase their freezing time compared to controls. However, the 7d memory retrieval test shows P90 stress rats but not P26 stress rats freeze while in the fear context. Twenty minutes after the memory retrieval test, hippocampi and amygdala were micro-dissected and prepared for western blot analysis. Our results show that 1d fear memory retrieval induced an upregulation of PSD-95 and pS295 in the adult amygdala but not in the juvenile. However, the juvenile animals upregulated PKMζ, PI3K and GluA2/3, GluA1-S845 in the dorsal hippocampus (DH), but the adults did not. Following the 7d memory retrieval test, adults upregulated GluA2 in the amygdala but not the juveniles. In the DH, adults increased PSD-95 and pS295 but not the juveniles. The adults appear to preferentially increase amygdala-driven processing at 1d and increase DH-driven context speciﬁc processing at 7d. These data identify molecular processes that may underlie the reduced fear-memory retrieval capability of juveniles. Together these data provide a potential molecular target that could be beneﬁcial in treatment of anxiety disorders and PTSD.
Zanca, Roseanna M.; Sanay, Shirley; Avila, Jorge A.; Rodriguez, Edgar; Shair, Harry N.; and Serrano, Peter A., "Contextual fear memory modulates PSD95 phosphorylation, AMPAr subunits, PKMζ and PI3K diﬀerentially between adult and juvenile rats" (2018). CUNY Academic Works.