Fig. 9. Schematic representation of hypothetical paracrine actions of the anterior commissural organ (ACO) in the commissural ganglion (CoG). In addition to serving as a source of CabTRP Ia to the hemolymph, some portions of the ACO terminate directly on areas of synaptic neuropil, and this structure may thus also function as a paracrine modulator of intrinsic CoG targets. One potential role for this paracrine signaling is the coordination of multiple neuroendocrine systems. The soma of the large (L)-cell, which projects to and innervates the pericardial organ (PO), is located within the CoG and is known to arborize in the vicinity of the ACO. Likewise, anterior commissural neurons 1 and 2 (ACN1/2), which are the sole source of innervation to the anterior cardiac plexus (ACP), are also located in the CoG and arborize near the ACO. If these neurons are modulated by CabTRP Ia, then elements of at least two other neuroendocrine centers could be modulated/synchronized locally within the CoG, concurrent with the release of CabTRP Ia from the ACO into the circulatory system. Non-endocrine neurons within the CoG [specifically CoG projection neurons (CPN) that innervate and modulate the stomatogastric neural circuit] may also be targets of paracrine signals from the ACO. If these neurons are influenced by CabTRP Ia released from the ACO, then a profound reorganization of the motor patterns produced by the motor neurons (MN) of the circuits contained within the stomatogastric ganglion could occur. Abbreviations not defined in this legend are as per Fig. 1.