Tyrosine hydroxylase‐like immunoreactivity in the brain of fifth instar Rhodnius prolixus stål (hemiptera: Reduviidae)

Abstract

The distribution of tyrosine hydroxylase-like immunoreactivity was mapped in whole-mount preparations of the brain of fifth instar Rhodnius prolixus Stål. Immunoreactivity was limited to neuronal cell bodies and processes, which were distributed over both ventral and dorsal surfaces of the CNS. The brain, excluding the optic lobes, contained about 160 tyrosine hydroxylase-like immunoreactive cells. Each optic lobe contained two groups of small round cell bodies, which were too numerous to count. The wide distribution of immunoreactivity suggests that tyrosine hydroxylase is present in neurons with diverse central functions. Tyrosine hydroxylase is the rate-limiting enzyme in catecholamine synthesis in vertebrates. A comparison of a map of the distribution of catecholamine-induced fluorescence obtained using the glyoxylic-acid technique (Flanagan; J. Insect Physiol. 30(9):697-704, 1984) with that generated for tyrosine hydroxylase reveals considerable overlap between the two systems, suggesting that tyrosine hydroxylase is used in the catecholamine pathway in this insect. The mapping of these reactive neurons is an important step for identification of unique tyrosine hydroxylase-containing neurons, and is our initial step in the analysis of identified catecholamine-containing neurons in R. prolixus.