Neuronal Network Inactivity Potentiates Neuropeptide Release from Mouse Cortical Neurons

Neurons adapt to chronic activity changes by modifying synaptic properties, including neurotransmitter release. However, whether neuropeptide release via dense core vesicles (DCVs)-a distinct regulated secretory pathway-undergoes similar adaptation remains unclear. Here, we demonstrate that 24 h action potential blockade leads to significant DCV accumulation in primary mouse cortical neurons of both sexes. Reactivation with action potential trains induced enhanced Ca²⁺ influx and 700% more DCV exocytosis compared with control neurons. Notably, total DCV cargo protein levels were unchanged, while mRNA levels of corresponding genes were reduced. Blocking neurotransmitter release with Tetanus toxin induced DCV accumulation, similar to that induced by network silencing with TTX. Hence, chronic network silencing triggers increased DCV accumulation due to reduced exocytosis during silencing. These accumulated DCVs can be released upon reactivation resulting in a massive potentiation of DCV exocytosis, possibly contributing to homeostatic mechanisms.