Identification of immunoreactive neurophysin-like proteins in the central nervous system of an insect; Locusta migratoria

Immunocytochemical localization of peptidergic cells in the neuro-endocrine system of the Colorado potato beetle, Leptinotarsa decemlineata, with antisera against vasopressin, vasotocin and oxytocin

Antisera against vasopressin, vasotocin, oxytocin, neurophysin-1 and neurophysin-2 were used to investigate immunocytochemically the presence of neurons containing substances antigenically related to these peptides in the nervous system of the Colorado potato beetle. Ten different antisera were used, four against vasopressin, three against oxytocin and one against vasotocin, neurophysin-1, and neurophysin-2. Immunoreactivity was shown by all antisera except those against the neurophysins. The vasopressin antisera all gave different results. One antiserum revealed only a single neuron pair, whereas others revealed in addition one or two other different cell groups. The oxytocin antisera likewise revealed different neurons. The fixation procedure influenced the outcome of the immunocytochemical reaction. Immunoreactivity as revealed by vasopressin, vasotocin and oxytocin antisera is often co-localized in the same neurons; solid phase adsorptions showed that this is due to cross-reactivity of the antisera. Some of the immunoreactive neurons are identical to those recently described to contain a bovine pancreatic polypeptide/FMRFamide-like peptide. This co-localization is probably not due to a cross-reaction. These findings indicate the presence of several vasopressin-like and oxytocin-like substances which in the Colorado potato beetle all have a different degree of immunocytochemical resemblance to vasopressin and oxytocin.

Biochemical characterization of a vasopressin-like neuropeptide in Locusta migratoria. Evidence of high molecular weight protein encoding vasopressin sequence

The biochemical characterization of a diuretic neurohormone, immunologically related to the mammalian vasopressin (AVP) and present in Locusta migratoria has been performed. The results have been obtained using an AVP radioimmunoassay as method of detection and quantification. The "AVP like" molecule exhibits the same C terminal moiety: the tetrapeptide 1/2 Cys-PrO-Arg-Gly NH2. 125I-radiolabelling allows us to demonstrate the presence of a tyrosyl residue. The molecular weight of this molecule is estimated by gel filtration to 2500 +/- 400 Daltons. The isoelectric point is 7.5 and the electrophoretic migration lead to conclude to the presence of amino acid residues lacking in the vasopressin hormone. We have demonstrated the presence of a vasopressin sequence included in high molecular weight protein which have been quantified in suboesophageal ganglion (biosynthetic site) and in the nervous ventral cord (release site).