IMMUNOHISTOCHEMICAL LOCALIZATION OF TYROSINE-HYDROXYLASE IN THE VENTRAL NERVE CORD OF THE STICK INSECT, CARAUSIUS-MOROSUS, INCLUDING NEURONS INNERVATING THE SALIVARY-GLANDS

The distribution df tyrosine hydroxylase-like immunoreactive neurons i s mapped in the ventral nerve cord of the stick insect, Carausius moro sus: This study also examines the tyrosine hydroxylase- and serotonin- like immunoreactive elements in the salivary glands of Carausius moros us. Tyrosine hydroxylase is the first and rate-limiting enzyme in the pathway for the production of catecholamines; therefore, tyrosine hydr oxylase-like immunoreactive neurons are likely to contain catecholamin es. Approximately 225 tyrosine hydroxylase-like immunoreactive neurons are present in the ventral nerve cord. The majority of these neurons appear to be interneurons. The suboesophageal ganglion contains the on ly unpaired neuron and the only pair of peripherally projecting tyrosi ne, hydroxylase-like immunoreactive neurons in the ventral nerve cord. The peripherally projecting neurons project to the Salivary glands vi a the salivary nerve. Each neuron in this pair is termed the salivary neuron 1. The remaining tyrosine hydroxylase-like immunoreactive neuro ns in the ventral nerve cord are interneurons and exhibit a characteri stic distribution within the thoracic and the abdominal ganglia. Serot onin-like immunoreactivity is also present in the salivary glands. Pos itive staining of the suboesophageal ganglion for serotonin-like immun oreactivity indicates the presence of several neuron pairs including a large pair along the ventral posterior midline that project to the sa livary glands via the salivary nerve. Each neuron in this pair is term ed the salivary neuron 2. Backfilling of the salivary nerve with cobal t chloride reveals the presence of only two neurons within the suboeso phageal ganglion that project to the salivary glands; these neurons ar e the salivary neurons 1 and 2. Reverse-phase high-performance liquid chromatography coupled with electrochemical detection of ventral nerve cord and salivary gland homogenates confirms the presence of dopamine and serotonin.