Immunoreactivity to the antiserum to the mammalian neuropeptide substance P in the central nervous system of the house fly, Musca domestica
Localization of immunoreactivity to the antiserum to the mammalian neuropeptide substance P in the central nervous system of the house fly, Musca domestica, was investigated by immunocytochemical methods. In both the larva and the adult a total of 16 neurons reacted positively against substance P antiserum. Of these, 10 were in the brain and 6 in the thoracic ganglia. The neurons were arranged in bilateral pairs. In the larval nervous system each brain lobe contained a cluster of four pairs of immunoreactive neurons in the dorsal protocerebrum, and the subesophageal ganglion and each of the thoracic neuromeres contained one pair each. The adult nervous system possessed the same number of imunoreactive neurons with identical distribution within the subesophageal and thoracic ganglia. However, the position of the protocerebral neurons was slightly altered. The pattern of immunoreactive axonal processes as well as the very high immunoreactivity observed in the dorsal neural sheath of the adult thoracic ganglion suggest a neurohormonal–neuromodulator role for substance P in this insect.