Coexistence of egg-laying hormone and a-bag cell peptide in bag cell neurons of Aplysia indicates that they are a peptidergic multitransmitter system

Abstract Double-label immunocytochemistry reveals that immunoreactivity for two putative peptide transmitters, egg-laying hormone and a -bag cell peptide 1–9 , co-exist in most bag cell somata and processes in the abdominal ganglion of the marine mollusc Aplysia . Together with previous physiological and biochemical data these findings indicate that the neuroendocrine bag cells are a multitransmitter system which utilizes two or more peptides derived from a common precursor.