Acetylcholine α7 Nicotinic and Dopamine D2 Receptors Are Targeted to Many of the Same Postsynaptic Dendrites and Astrocytes in the Rodent Prefrontal Cortex

The alpha-7 nicotinic acetylcholine receptor (alpha 7nAChR) and the dopamine D-2 receptor (D2R) are both implicated in attentional processes and cognition, mediated in part through the prefrontal cortex (PFC). We examined the dual electron microscopic immunolabeling of alpha 7nAChR and either D2R or the vesicular acetylcholine transporter (VAChT) in rodent PFC to assess convergent functional activation sites. Immunoreactivity (ir) for alpha 7nAChR and/or D2R was seen in the same as well as separate neuronal and glial profiles. At least half of the dually labeled profiles were somata and dendrites, while most labeled axon terminals expressed only D2R-ir. The D2R-labeled terminals were without synaptic specializations or formed inhibitory or excitatory-type synapses with somatodendritic profiles, some of which expressed the alpha 7nAChR and/or D2R. Astrocytic glial processes comprised the majority of nonsomatodendritic alpha 7nAChR or alpha 7nAChR and D2R-labeled profiles. Glial processes containing alpha 7nAChR-ir were frequently located near VAChT-labeled terminals and also showed perisynaptic and perivascular associations. We conclude that in rodent PFC alpha 7nACh and D2R activation can dually modulate (1) postsynaptic dendritic responses within the same or separate but synaptically linked neurons in which the D2R has the predominately presynaptic distribution, and (2) astrocytic signaling that may be crucial for synaptic transmission and functional hyperemia. Synapse 65:1350-1367, 2011. (C) 2011 Wiley-Liss, Inc.