Heroin self-administration and extinction increases prelimbic cortical astroglia-synapse proximity and alters dendritic spine morphometrics that are reversed by N-acetylcysteine

Abstract

Clinical and preclinical studies indicate that adaptations in corticostriatal neurotransmission significantly contribute to heroin relapse vulnerability. In animal models, heroin self-administration and extinction produce cellular adaptations in both neurons and astrocytes within the nucleus accumbens (NA) core that are required for cue-induced heroin seeking. Specifically, decreased glutamate clearance and reduced association of perisynaptic astrocytic processes with NAcore synapses allow glutamate release from prelimbic (PrL) cortical terminals to engage synaptic and structural plasticity in NAcore medium spiny neurons. Normalizing astroglial glutamate homeostasis with drugs like the antioxidant N-acetylcysteine (NAC) prevents cue-induced heroin seeking. Surprisingly, little is known about heroin-induced alterations in astrocytes or pyramidal neurons projecting to the NAcore in the PrL cortex (PrL-NAcore). Here, we observed increased complexity of the glial fibrillary acidic protein (GFAP) cytoskeletal arbor and increased association of the astroglial plasma membrane with synaptic markers following heroin SA and extinction training in the PrL cortex. Repeated treatment with NAC during extinction reversed both the enhanced astroglial complexity and synaptic association. In PrL-NAcore neurons, heroin SA and extinction decreased apical tuft dendritic spine density and enlarged dendritic spine head diameter in male Sprague-Dawley rats. Repeated NAC treatment during extinction prevented decreases in spine density but not dendritic spine head expansion. Moreover, heroin SA and extinction increased co-registry of the GluA1 subunit of AMPA receptors in both the dendrite shaft and spine heads of PrL-NAcore neurons. Interestingly, accumulation of GluA1 immunoreactivity in spine heads was further potentiated by NAC treatment during extinction. Taken together, our data reveal circuit-level adaptations in cortical dendritic spine morphology potentially linked to heroin-induced alterations in astrocyte complexity and association at synapses. Additionally, these data demonstrate, for the first time, that NAC reverses PrL cortical heroin SA and extinction-induced adaptations in both astrocytes and corticostriatal neurons.