Fig. 11. Synapsin-like labeling is restricted to FLRFamide-immunopositive terminals in the anterior cardiac plexus (ACP). Five axons are present in the portion of the anterior cardiac nerve containing the ACP. Four of the five axons are FLRFamide immunopositive and contribute innervation to the ACP. To assess whether the remaining axon contributes to the innervation of the ACPs, double-immunolabels pairing FLRFamide and synapsin antibodies were conducted. In all preparations, the synapsin label was found localized in FLRFamide-immunopositive terminals. Most FLRFamide labeled terminals exhibited some degree of synapsin staining. In no preparation were any terminals found that contained only synapsin immunoreactivity. Interestingly, within a given terminal, the FLRFamide and synapsin labels are often non-uniformly segregated. (A1–3) and (B1–3) show examples of this localization from two different preparations. (A1–3) Brightest pixel projections of 19 optical sections taken at 1.0 µm intervals. (A1) FLRFamide immunoreactivity pseudocolored red. (A2) Synapsin immunoreactivity pseudocolored green. The optical sections used to produce A1 and A2 were simultaneously collected from the same focal planes. (A3) A merged image of A1 and A2. Profiles exhibiting only FLRFamide or synapsin immunolabeling appear red or green, respectively. Structures showing coincidence of FLRFamide and synapsin labels appear yellow (or shades thereof). (B1–3) Brightest pixel projection of 12 optical sections taken at 1.0 µm intervals. Organization and pseudocoloring of B1–3 is identical to that of A1–3. Scale bar, 50 µm.