Terminal arborisation

Two recent studies have shown that proctolin has a potent stimulating effect on the visceral muscles of the oviduct in Rhodnius prolixus (33,34) and in the stable fly Stomoxvs calcitrans (35). In both of these insects, reverse-phase HPLC and quantitative bioassay were used to demonstrate the presence of a proctolin-like substance in extracts of the reproductive tissues. Immunohistochemical preparations revealed intense proctolin-like immunoreactivity in terminal arborisations of nerves on the spermathecae, common oviduct and bursa of Rhodnius. The muscles of the ovarian sheath in stably fly responded to proctolin, and 0.5 to... 

The large diameter A/l-afferent fibre enters the dorsal horn of the spinal cord through the medial division of the dorsal root. It then descends through the medial region of lamina I or II, or alternatively, curves around the medial (central) edge of the dorsal horn down to the ventral horn. On reaching deeper laminae, laminae IV and V, the AjS-fibres ascend back up into laminae III and IV where they repeatedly subdivide and form a characteristic termination pattern. The densest arborisation appears to occur in lamina III. Axons originating from specialised muscle stretch receptors have collaterals that pass ventrally to make monosynaptic connections with neurons of laminae V, VI and VII. Some also extend to laminae VIII and IX of the ventral horn where they synapse directly onto motor neurons and form the basis of monosynaptic reflexes. 

We do not know whether the retiaal cells are able to reestablish a fidl and healthy TH-content after lead exposure is terminated and whether the synaptic wiring is affected irreversibly by lead-induced intoxication. Although TH-immunoreactive cells have some capacity to restore their TH-synthesis after intoxication the receptive fields of these reanimated cells are smaller, and arborisation of processes less pronounced. 

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