The avian homologs of arginine vasopressin (AVP) and oxytocin (OT) are arginine 
vasotocin (AVT) and mesotocin (MT), respectively. In birds, AVT shares many of 
the functions of AVP including regulation of fluid balance, blood pressure 
regulation and the stress response. AVT also plays an oxytocin-like reproductive 
role in birds by stimulating uterine (shell gland) contraction during 
oviposition. The role of MT in avian reproduction is not clear. Here, we report 
the cloning of a third neuropeptide receptor in the chicken (Gallus gallus). 
Parsimony analysis reveals that the new receptor has highest homology to 
mammalian OT receptors and the MT receptors of non-mammalian vertebrates. 
Moreover, the receptor bears far less homology to the two avian VT receptors 
that have been cloned. Reverse transcription-polymerase chain reaction and in in 
situ hybridization analyses reveal the receptor is expressed in both the 
endometrium and myometrium of the shell gland. The expression pattern and high 
homology to OT receptors suggest that the receptor may stimulate myometrial 
contraction and therefore play a critical role in oviposition.