Astrocytic 5-HT1A receptor mediates age-dependent hippocampal LTD and fear memory extinction in male mice

NMDA receptor-dependent long-term depression (LTD) in the hippocampus is a well-known form of synaptic plasticity that has been linked to different cognitive functions. Although the underlying mechanisms remain unclear, this form of LTD cannot be induced by low-frequency stimulation (LFS) in adult mice. In this study, we found that LFS-induced LTD was not easily induced in adult animals and was age dependent. Interestingly, the level of the 5-HT1A receptor was correspondingly increased and exhibited an inverse correlation with the magnitude of LFS-LTD during development. Knockout or pharmacological inhibition of the 5-HT1A receptor reversed impaired LFS-LTD in adult mice (P60), while activation or inhibition of this receptor disturbed or enhanced LFS-LTD in adolescent mice (P21), respectively. Furthermore, the astrocytic 5-HT1A receptor in the hippocampus predominantly mediated age-dependent LFS-LTD through enhancing GABAergic neurotransmission. Finally, fear memory extinction differed among the above conditions. These observations enrich our knowledge of LTD at the cellular level and suggest a therapeutic approach for LTD-related psychiatric disorders. Understanding how our brains learn and remember is intriguing. As we age, our learning and memory abilities can alter, and scientists are trying to understand why. A recent study investigates this by studying a specific brain receptor, the 5-HT1A receptor, and its effect on learning and memory in mice. The team focused on a process called long-term depression. They found that the ability to induce LTD changes with age and that the 5-HT1A receptor plays a key role in this. They discovered that the activity of 5-HT1A receptors in certain brain cells, astrocytes, is necessary for LTD and influences fear memory extinction. The researchers conclude that the 5-HT1A receptor in astrocytes plays a crucial role in regulating learning and memory processes related to LTD. This discovery could lead to new treatments for memory-related disorders. This summary was initially drafted using artificial intelligence, then revised and fact-checked by the author.