Physiological and morphological properties of interneurones in the deutocerebrum of male cockroaches which respond to female pheromone

Summary Interneurones in the deutocerebrum of male cockroaches were characterised according to their intracellularly recorded responses to odours of females and to selected food odours. Following physiological characterization the interneurones were stained by the intracellular injection of dye. Some interneurones were characterized by extracellular recording and staining.The intracellular electrodes were either placed in the somata of the interneurones or more usually in neurites between the deutocerebral glomeruli. Such recordings reveal a continuous background of synaptic potentials, and spikes at a variable but low frequency depending upon the individual interneurone. The odours, which were blown over one antenna, were a whole female extract and two purified components of this; Fraction A and a second identical to Periplanone B. Sixteen other food odours were also tested. The interneurones revealed fell into four main groups which responded to: the whole female extract and the two components, to one of the two components preferentially, and to whole female extract but neither of the components. Other interneurones were inhibited by female odours but excited by some food odours. The interneurones with these characteristics which were stained, were principal interneurones with cell bodies in the lateral cluster in the deutocerebrum, branches within the deutocerebrum confined to the macroglomerulus (an enlarged glomerulus found only in adult males), and an axon projecting to the calyces and lobus lateralis protocerebralis of the protocerebrum. The interneurones responding preferentially to Periplanone B had branches throughout the macroglomerulus, but those responding to Fraction A had a more restricted pattern of branching within the macroglomerulus.