A VIP-like peptide co-occurs with substance P and enkephalin in cholinergic preganglionic terminals of the avian ciliary ganglion.

Using single-label and double-label immunohistochemical techniques, many of the substance P-enkephalin containing preganglionic terminals of the avian ciliary ganglion were found to also contain a VIP-like peptide. Since these terminals are also known to be cholinergic, these results suggest that neurotransmission at many synapses of the avian ciliary ganglion involves 3 different neuropeptides and a conventional neurotransmitter, acetylcholine.