Neuronal nicotinic acetylcholine receptor subunits in autism: An immunohistochemical investigation in the thalamus

The cholinergic system has been implicated in the development of autism on the basis of neuronal nicotinic acetylcholine receptor (nAChR) losses in cerebral and cerebellar cortex. In the present study, the first to explore nAChRs in the thalamus in autism, alpha 4, alpha 7 and beta 2 nAChR subunit expression in thalamic nuclei of adult individuals with autism (n = 3) and age-matched control cases (n = 3) was investigated using immunochemical methods. Loss of alpha 7- and beta 2- (but not alpha 4-) immunoreactive neurons occurred in the paraventricular nucleus (PV) and nucleus reuniens in autism. Preliminary results indicated glutamic acid decarboxylase immunoreactivity occurred at a low level in PV, co-expressed with alpha 7 in normal and autistic cases and was not reduced in autism. This suggested loss of neuronal alpha 7 in autism is not caused by loss of GABAergic neurons. These findings indicate nicotinic abnormalities that occur in the thalamus in autism which may contribute to sensory or attentional deficits. (c) 2005 Elsevier Inc. All rights reserved.