Periviscerokinins mediate visceral muscle contractile activity (myotropic activity). Periviscerokinin 1 and 2 are expressed in central brain, antennal lobes and gnathal, thoracic and abominal ganglia. Periviscerokinin 2 is also expressed in the retrocerebral complex (at protein level). A pyrokinin potentially constituted by residues Asn-158 to Gly-170 has so far not been detected and might be completely absent in ants. Periviscerokinin 1. Periviscerokinin 2.