ITP-protein is expressed in adult pacemaker neurons LNd and Pdf negative s-LNV neuron. Labeling in the cell body is detected throughout the circadian light-/dark-cycle while staining at the axon terminals is strongest at Zeitgeber time 5, 8 and 20.

ITP labels the projection of the fifth Pdf-negative s-LNv neuron to the medulla and lamina. The terminals in the lamina are near the retina, in the region of the lamina monopolar cells. In addition, there is more widespread staining of the medulla.

ITP is co-expressed with a dimm reporter and the Kurs-6 enhancer trap in ipc-1 and ipc-2a neurons.

ITP protein is expressed in the 5th PDF negative s-LNV neuron and in one of the neurons of the LNd cluster. This LNd neuron also expresses ScerGAL4^npf.4.5 (only in males) and ScerGAL4^Mai179.

There are a maximum of 9 (but normally 8) ITP immunoreactive bilateral neuron pairs in the larval and prepupal central nervous system which are found in dorso-mediolateral positions close to the posterior edges of the calyces of the mushroom body. These neurons, referred to as the ipc-1 neurons, project their axons ipsilaterally to terminate posterior to the ring gland, branch within the corpa cardiaca and terminate on the walls of the anterior aorta. Dendrites emerge medially almost at right angles from the axons and extend in a posterioventral direction and, upon reaching the midline, these fibres continue caudally to terminate in the subesophageal ganglion. One fibre on each side continues without branching through the prothoracic gland and terminate in the corpa allatum. In the adults, there are a maximum of 14 ITP immunoreactive neurons in the protocerebrum. The four pairs of adult ipc-1 neurons are located in a posteriodorsal and mediolateral position within the protocerebrum. They project axons to the retrocerebral complex and other putative neurohemal areas in the dorsal sheaths of the neck connective and thoracic parts of the ventral nerve cord. These neurons also give off side branches that innervate median neuropils surrounding the esophageal orifice. The main axon bundle ipsilaterally joins the nervus corporis cardiaci. Some branches of the main axons continue to make terminals at the dorsal surface of the thoracic ganglia or run within lateral stomatogastric nerves along the proventriculus, continue along thoracic parts of the gut and terminate in the vicinity of the salivary glands. Three other groups of protocerebral neurons are ITP immunoreactive: four ipc-2 neurons, which are found dorso-posteriomedially, give rise to short fibres that cross the midline at the level of the protocerebral bridge, with two fibres running dorsally and caudally to intertwine with the ipc-1 neurons; three to four pairs of ipc-3 extending processes through the superior medial and lateral protocerebrum. Their cell bodies are located close to the anterior lateral and anterior dorsal bases of the medulla. At least the most anteriorly and ventrally positioned neuron projects lateral branches into the accessory medulla; one bilateral, faintly staining ITP immunopositive pair of neurons, called the ipc-4, are found in a dorsomedial position with short projections into protocerebral bridge associated neuropils. These neurites extend along the median bundle to areas around the esophageal orifice. In the ventromedial area of the larval and prepupal subesophageal ganglion, a prominent pair of ITP immunoreactive neurons are found that send projections running to the dorsal side and span almost the entire ventral nerve cord. These neurons lose their immunoreactivity during the pupal stage. Located in the eighth abdominal neuromere, three or four pairs of ITP immunoreactive neurons are seen in larvae, prepupae and adults. The axons of these cells extend first into the medial neuropils and then leave the ventral nerve cord through the eighth abdominal nerve and probably innervate the hindgut. Along the lateral body wall, next to the border of abdominal segments A7 and A8, a pair of bipolar peripheral ITP immunopositive neurons can be seen in larvae and prepupae. In adults, this neuron is located on the dorsal perineural side and close to the roots of the dorsal lateral wing and haltere nerves. This neuron sends one branchless axon along the nerves into the periphery and one axon back into the thoracoabdominal ganglion mass where they branch and terminate in the dorsal perineural sheath.