Fig. 6.

Intracellular recordings showing the responses of a local interneuron (LN) to antennal stimulation with pheromone. a The LN is inhibited by antennal stimulation with either bombykal (BAL), C15, or a blend of both pheromone components. Likewise, an extract of the pheromone gland of a female conspecific inhibits this LN. This neuron is able to track an intermittent odorant stimulus at a frequency of at least 5 Hz. Note the distinct periods of inactivity (arrows) evoked by consecutive odorant pulses. b In this neuron, stimulation with the pheromone blend at depolarized membrane potentials evokes a brief inhibitory response corresponding to each stimulus pulse. c Morphology of the local interneuron shown in (a, c) (frontal view). The LN has branches throughout the entire antennal lobe, except the MGC. C cumulus, do dorsal, la lateral, T1 toroid-1. Scale bar 100 μm. d Summary diagram of pheromone and odorant responses in the AL of male Manduca. Stimulation with C15 evokes a primarily excitatory response in neurons innervating the cumulus and an inhibition in neurons ramifying in the toroid-1 and other AL glomeruli. In contrast, stimulation with bombykal activates neurons in the toroid-1 and inhibits all other neurons in the AL, namely those in the cumulus and ordinary glomeruli. Projection neurons that branch in the MGC do not respond to plant odorants, whereas neurons (uPNs and LNs) that innervate ordinary glomeruli respond with excitation to plant odorants