NERVOUS CONTROL OF JUVENILE-HORMONE BIOSYNTHESIS IN LOCUSTA-MIGRATORIA

In Locusta migratoria migratorioides R. and F., two types of brain neu rons innervate the juvenile hormone (JH)-producing corpora allata (CA) . Thirteen cells in each pars lateralis (PL) innervate the ipsilateral CA, while four cells (two in each PL) innervate both glands. We inves tigated possible influences of these two neuronal types on JH producti on by a newly developed method. A radiochemical assay was used to meas ure hourly JH production by a CA with intact nerve connections to the brain. Then, changes in hormone production due to selective nerve stim ulation or transection were assessed. In control preparations JH produ ction per h remained approximately constant for at least 9 h. Simultan eous electrical stimulation of all neurons innervating one CA (i.e., 1 3 ipsilateral plus 4 bilaterally innervating cells) always inhibited J H production, while their transection led to a rapid progressive incre ase in JH biosynthesis in CA from females with oocytes longer than 4.5 mm. Thus, there is strong neurally mediated inhibition of the CA at c ertain phases of the vitellogenic cycle. The dramatic effects of nerve transection show that in vitro rates of JH production are an unreliab le indicator of in vivo levels. Selective stimulation of the four neur ons innervating both CA suggests that they do modulate JH biosynthesis but the effect varies qualitatively depending on the phase of the vit ellogenic cycle.