Cocaine triggers glial-mediated synaptogenesis
Synaptogenesis is essential in forming new neurocircuits during development, and this is mediated in part by astrocyte-released thrombospondins (TSPs) and activation of their neuronal receptor, 2{delta}-1. Here, we show that this developmental synaptogenic mechanism is utilized during cocaine experience to induce spinogenesis and the generation of AMPA receptor-silent glutamatergic synapses in the adult nucleus accumbens (NAc). Specifically, cocaine administration activates NAc astrocytes, and preventing this activation blocks cocaine-induced generation of silent synapses. Furthermore, knockout of TSP2, or pharmacological inhibition or viral-mediated knockdown of 2{delta}-1, prevents cocaine-induced generation of silent synapses. Moreover, disrupting TSP2-2{delta}-1-mediated spinogenesis and silent synapse generation in the NAc occludes cue-induced cocaine seeking after withdrawal from cocaine self-administration and cue-induced reinstatement of cocaine seeking after drug extinction. These results establish that silent synapses are generated by an astrocyte-mediated synaptogenic mechanism in response to cocaine experience and embed critical cue-associated memory traces that promote cocaine relapse.