This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. A c c e p t e d M a n u s c r i p t 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 Although some of the neural circuits involved in the acute and chronic effects of nicotine have been identified, much less is known about which native nAChR subtypes are involved in specific physiological functions and pathophysiological conditions.We briefly review some recent findings concerning the structure and function of native nAChRs, focusing on the subtypes identified in the meso-striatal and habenulo-interpeduncular pathways, two systems involved in nicotine reinforcement and withdrawal. We also discuss recent findings concerning the effect of chronic nicotine on the expression of native subtypes.

Recent studies suggest that the neuronal nicotinic receptors (nAChRs) present in the habenulo-interpeduncular (Hb-IPn) system can modulate the reinforcing effect of addictive drugs and the anxiolytic effect of nicotine. Hb and IPn neurons express mRNAs for most nAChR subunits, thus making it difficult to establish the subunit composition of functional receptors. We used immunoprecipitation and immunopurification studies performed in rat and wild-type (ϩ/ϩ) and ␤2 knock-out (Ϫ/Ϫ) mice to establish that the Hb and IPn contain significant ␤2* and ␤4* populations of nAChR receptors (each of which is heterogeneous). The ␤4* nAChR are more highly expressed in the IPn. We also identified novel native subtypes (␣2␤2*, ␣4␤3␤2*, ␣3␤3␤4*, ␣6␤3␤4*). Our studies on IPn synaptosomes obtained from ϩ/ϩ and ␣2, ␣4, ␣5, ␣6, ␣7, ␤2, ␤3, and ␤4 Ϫ/Ϫ mice show that only the ␣3␤4 and ␣3␤3␤4 subtypes facilitate acetylcholine (ACh) release. Ligand binding, immunoprecipitation, and Western blotting studies in ␤3 Ϫ/Ϫ mice showed that, in the IPn of these mice, there is a concomitant reduction of ACh release and ␣3␤4* receptors, whereas the receptor number remains the same in the Hb. We suggest that, in habenular cholinergic neurons, the ␤3 subunit may be important for transporting the ␣3␤4* subtype from the medial habenula to the IPn. Overall, these studies highlight the presence of a wealth of uncommon nAChR subtypes in the Hb-IPn system and identify ␣3␤4 and ␣3␤3␤4, transported from the Hb and highly enriched in the IPn, as the subtypes modulating ACh release in the IPn.

SummaryHaploinsufficiency of SHANK3, encoding the synapse scaffolding protein SHANK3, leads to a highly penetrant form of Autism Spectrum Disorder (ASD). How SHANK3 insufficiency affects specific neural circuits and this is related to specific ASD symptoms remains elusive. Here we used shRNA to model Shank3 insufficiency in the Ventral Tegmental Area (VTA) of mice. We identified dopamine (DA) and GABA cell-type specific changes in excitatory synapse transmission that converge to reduce DA neuron activity and generate behavioral deficits, including impaired social preference. Administration of a positive allosteric modulator of the type 1 metabotropic glutamate receptors (mGluR1) during the first postnatal week restored DA neuron excitatory synapse transmission and rescued the social preference defects, while optogenetic DA neuron stimulation was sufficient to enhance social preference. Collectively, these data reveal the contribution of impaired VTA function to social behaviors and identify mGluR1 modulation during postnatal development as a potential treatment strategy.

The cellular mechanism(s) underlying autism spectrum disorders (ASDs) are not fully understood although it has been shown that various genetic and environmental factors contribute to their etiology. As increasing evidence indicates that astrocytes and microglial cells play a major role in synapse maturation and function, and there is evidence of deficits in glial cell functions in ASDs, one current hypothesis is that glial dysfunctions directly contribute to their pathophysiology. The aim of this review is to summarize microglia and astrocyte functions in synapse development and their contributions to ASDs.

Astrocytes orchestrate neural development by powerfully coordinating synapse formation and function and, as such, may be critically involved in the pathogenesis of neurodevelopmental abnormalities and cognitive deficits commonly observed in psychiatric disorders. Here, we report the identification of a subset of cortical astrocytes that are competent for regulating dopamine (DA) homeostasis during postnatal development of the prefrontal cortex (PFC), allowing for optimal DA-mediated maturation of excitatory circuits. Such control of DA homeostasis occurs through the coordinated activity of astroglial vesicular monoamine transporter 2 (VMAT2) together with organic cation transporter 3 and monoamine oxidase type B, two key proteins for DA uptake and metabolism. Conditional deletion of VMAT2 in astrocytes postnatally produces loss of PFC DA homeostasis, leading to defective synaptic transmission and plasticity as well as impaired executive functions. Our findings show a novel role for PFC astrocytes in the DA modulation of cognitive performances with relevance to psychiatric disorders.