Protocerebral neurons inhibiting proliferation of corpus allatum cells in the cockroach, Diploptera punctata

A mitotic wave before an increase in juvenile hormone (JH) synthesis was ob served in the corpora allata during each ovarian cycle in the cockroach Dip loptera punctata and was shown subsequently to be inhibited by the brain un til adult females mated. Each corpus allatum (CA) was innervated by groups of neurons in the contralateral pars intercerebralis (PI) and the ipsilater al pars lateralis (PL). In this article, a third set of neurons is identifi ed that innervates the CA located extralaterally in the contralateral FL. T he topography of the brain neurons innervating the CA was reconstructed fro m confocal optical sections after vital staining with two fluorescent carbo cyanine dyes, 1,1'-dihexadecyl-3,3,3',3'-tetramethylin carbocyanine perchlo rate [DiIC(16) (3)] and 3,3'-dioctadecyloxacarbocyanine perchlorate [DiOC(1 8) (3)]. This provided information necessary to disconnect specific pathway s within the brain of virgin females and to determine the effect on mitosis in the corpora allata and on the growth of oocytes. Disconnection of the C A from the PI neurons was followed by a prolonged period of moderate mitoti c activity in the glands. Disconnection of the CA from PI and contralateral PL neurons was followed by a rapid wave of high mitotic activity in the CA similar to that observed after mating. The ipsilateral PL neurons did not appear to influence CA cell proliferation, because mitotic activity in glan ds was similar whether or not glands were connected to these neurons. Disco nnection of the contralateral PI and/or ipsilateral PL neurons, but not the contralateral PL neurons, from the CA resulted in oocyte growth indicative of increased JH synthesis. The authors conclude that, whereas contralatera l PI neurons inhibit both CA cell proliferation and JH synthesis, ipsilater al PL neurons affect only JH synthesis, and contralateral PL neurons modula te cell proliferation slightly only. (C) 1999 Wiley-Liss, Inc.