The satellite nervous system ? an extensive neurohemal network in the locust head

Abstract

1. A modification of iontophoretic cobalt injection stained small diameter nerves originating from the SOG of the locust,Locusta migratoria (Figs. 1, 2 A, 2B). These small nerves were called satellites as they are intimately associated with the major peripheral nerves of the mouthparts and the labrum. They follow these nerves into distal regions. 2. The satellite nerves contain the axons of only three neurons on each side of the SOG (Fig. 2C). These neurons exhibit complex dendritic ramifications in the anterior region of the ganglion (Figs. 3, 4). In the periphery, they establish a dense and widely distributed meshwork of presumed neurohemal terminals on the outer surface of the peripheral nerves of the SOG and the tritocerebrum (Fig. 2D, E). 3. Satellite neurons produce action potentials of long duration (up to 30 ms), which suggests that they are neurosecretory cells. Nerve potentials correlated with satellite neuron activity can be recorded from all peripheral nerves in the ventral half of the head, even in extremely distal regions. Finlayson 1978). Other neurosecretory cells, located within the central nervous system, appear to innervate specific targets, i.e. they do not release their products into the hemolymph (e.g. Evans and O'Shea 1978; O'Shea and Adams 1981).