Influence of the target on distribution and functioning of the varicosities of Helix pomatia metacerebral cell C1 in dissociated cell culture

The serotonergic metacerebral giant cell (C1) of Helix pomatia was isolated with its bifurcate axon and plated in culture under five conditions: (i) w ith no target; (ii) with the appropriate target B2 near the stump of the bi gger branch (CBC); (iii) with B2 near the stump of the smaller branch (CC); (iv) with a wrong target (C3) near the stump of the CBC branch and (v) wit h B2 and C3 positioned near the CBC and CC stump, respectively. The countin g of anti-serotonin antibody-labelled varicosities of the C1 neuron showed that the presence of the appropriate target in either axonal domain both do wn-regulated the number of varicosities of the contralateral neuritic held, and increased their average size, whereas the wrong target induced an over all reduction of the number of C1 neuron varicosities, and inhibited the ev oked transmitter release. The action potential-evoked calcium concentration increase in the neuritic terminals of the C1 neuron cultured alone, or in presence of the appropriate target, reached a value significantly higher th an that reached in presence of the wrong target. These results provide evidence that the postsynaptic neuron regulates both morphological and functional development of presynaptic terminals. (C) 2000 IBRO. Published by Elsevier Science Ltd.