BACKGROUND: Arginine vasopressin (AVP) has been hypothesized to play a role in 
aetiology of autism based on a demonstrated involvement in the regulation of 
social behaviours. The arginine vasopressin receptor 1A gene (AVPR1A) is widely 
expressed in the brain and is considered to be a key receptor for regulation of 
social behaviour. Moreover, genetic variation at AVPR1A has been reported to be 
associated with autism. Evidence from non-human mammals implicates variation in 
the 5'-flanking region of AVPR1A in variable gene expression and social 
behaviour.
METHODS: We examined four tagging single nucleotide polymorphisms (SNPs) 
(rs3803107, rs1042615, rs3741865, rs11174815) and three microsatellites (RS3, 
RS1 and AVR) at the AVPR1A gene for association in an autism cohort from 
Ireland. Two 5'-flanking region polymorphisms in the human AVPR1A, RS3 and RS1, 
were also tested for their effect on relative promoter activity.
RESULTS: The short alleles of RS1 and the SNP rs11174815 show weak association 
with autism in the Irish population (P = 0.036 and P = 0.008, respectively). 
Both RS1 and RS3 showed differences in relative promoter activity by length. 
Shorter repeat alleles of RS1 and RS3 decreased relative promoter activity in 
the human neuroblastoma cell line SH-SY5Y.
CONCLUSIONS: These aligning results can be interpreted as a functional route for 
this association, namely that shorter alleles of RS1 lead to decreased AVPR1A 
transcription, which may proffer increased susceptibility to the autism 
phenotype.