Ultrastructural analysis of neurosecretory cells in the antennae of the mosquito, Culex salinarius (Diptera : Culicidae)

An antiserum raised against the peptide, culetachykinin II, immunocytochemi cally detected a group of neurosecretory cells in the first flagellar segme nt of the antennae of both males and females of the mosquito, Culex salinar ius. This is the first insect species in which neurosecretory cells have be en found in the antennae. The ultrastructure of these antennal neurosecreto ry cells (ANC) is described, as well as their relationship to other neurons in the antennae and antennal lobe of the mosquito. These tachykinin-reacti ve cells contain relatively small (140-220 nm) elementary neurosecretory gr anules. Not only do the ANC have axons that terminate on specific glomeruli of the deutocerebrum, but these neurons also have collaterals that form ne urohemal terminals in the receptor lymph channels of the dendrites of the s ensory neurons. Thus, the ANC not only influence higher centers of the brai n that interpret signals from the antennal sensillae, but also modulate the response of the sensory receptors. To our knowledge, this is the first rep ort of neurosecretory cells directly affecting the signal reception of sens ory neurons.