Autoradiographic localization of 5-hydroxytryptamine and noradrenaline in the central nervous system of Lithobius forficatus L. (Myriapoda; Chilopoda)

Using the ability of selective uptake by the neurons of their own secreted amines, two 3H labeled neurotransmitters were used: 5-hydroxytryptamine (5 HT, serotonin) and noradrenaline (NA). Autoradiographic study was conducted on semithin and on ultrathin sections. In the brain, 3H-5 HT labeling is observed in the frontal lobes of the protocerebrum (two pairs of neurons) and in the lateral areas of the deutocerebrum and tritocerebrum (three or four pairs of neurons). A pair of labeled neurons is also present in each ganglion of the posterior part of the ventral nerve cord. In the protocerebrum, 3H-NA is taken up by a pair of neurons located in the frontal lobes; two pairs of noradrenergic neurons can be found in each ganglion of the nerve cord. Labeled axons (5-HT and NA) are present in the brain and in the neuropils of the abdominal ganglions. The pathway of some cerebral axons can be followed in the perioesophageal connectives and in the cerebral glands. These results are in agreement with the effects of injected neurotransmitters on (1) the brain electrical activity and (2) the stimulated activity of some of the protocerebral neurons (ultrastructural study by Jamault-Navarro in preparation).