Heterogeneity of pituitary adenylate cyclase-activating polypeptide and vasoactive intestinal polypeptide receptors in rat intrinsic cardiac neurons.

The expression of receptors for pituitary adenylate cyclase-activating polypeptide (PACAP) and vasoactive intestinal polypeptide (VIP) was investigated in isolated parasympathetic neurons of neonatal rat intracardiac ganglia using single-cell reverse transcription-polymerase chain reaction. Individual neurons were shown to express multiple isoforms of the PACAP receptor, PAC1, including PAC1-short, -HOP1 and -HOP2 variants, which differ in the region encoding the G protein-binding domain. The PAC1-HOP1 isoform was the predominant species, being expressed at higher levels and in a greater number of cells than other PAC1 variants. In addition to PAC1, intrinsic cardiac neurons express transcripts for the VIP receptors, VPAC1 and VPAC2, with VPAC2 being found in a greater proportion of the neurons. These findings may explain the complex effects of PACAP and VIP on neuroexcitability in mammalian intracardiac ganglia.