Olfactory bulb ruffed cells

Central/Tertiary structures The fish olfactory bulb is a fourlayered structure much as in higher vertebrates. Within the 2nd layer, the first synapse for olfactory input is on the dendrites of the mitral cells (MC). About 1000 ORN axons converge on one MC, a ratio similar to mammals. The MC output, from cells at various levels, leads into several glomeruli and receives (inhibitory) input from granule cells. The latter also innervate a distinct cell type in the MC layer of teleosts — the ruffed cells (RC), with which they have reciprocal synapses [Fig. 2.18(a)] both relay cells send ascending fibres to forebrain centres (Kosaka and Hama, 1982). The RC are unlike the MC since they are not stimulated by the ORNs directly. Their interactions (Chap. 5) may contribute to the processing of pheromonal stimuli (Zippel, 2000). The main bulbar pathways project to several nuclei in the forebrain via two ipsilateral tracts, the lateral and medial [Fig. 2.18(b)], the latter mediates sexual behaviour and the former probably other behaviours (Hara,... 

Zippel H., Gloger M., Luthje L., Nasser S., et al. (2000). Pheromone discrimina ability of olfactory bulb mitral and ruffed cells in the goldfish. Chem Senses 339-349. 

Using electrophysiological techniques, we have examined the relationship between the two types of relay neurons. During penetration of the goldfish olfactory bulb, responses from mitral cells and ruffed cells could be recorded extracellularly and simultaneously in the plexiform layer with a single tungsten electrode. The activity of mitral cells depends on the input from olfactory receptor neurons. 

There is, however, no doubt that the contrasting interactions between mitral cells and ruffed cells play a dominant role in information processing. The more effective the stimulus, the greater the contrasting activity patterns from mitral cells and ruffed cells. This is the first simultaneously recording from different relay neurons in the olfactory bulb, because in goldfish mitral cells, and ruffed cells are not separately lying in different layers. 

Koasaka, T. Hama, K. 1979. Ruffed Cell A new type of neuron with a distinctive initial unmyelinated portion of the axon in the olfactory bulb of the goldfish (Carassius auratus) I. Golgi impregnation and serial thin sectioning studies. J. Comp. Neurol., 186, 301—320. 

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