Immunohistochemical Localization Of Serotonin And Tryptophan Hydroxylase In The Brain Of The Larval And Adult Cockroach, Blattella Germanica

The distribution of serotonin (5-HT) and Tryptophan hydroxylase in the brain of the cockroach Blattella germanica, also the compare among the first instar larvae, the last instar larvae and the adult cockroach, were studied by means of the Colophony-paraffin (CP)embedding serial section technique and the Streptavidin-peroxidase (SP) immunohistochemical method. The results show that the brain is developed, and serotonin is widely distributed throughout all areas of the brain. The number of serotonin-like immunoreactive somata in the brain is a bit small, and the positive neurons are mainly symmetrically localized protocerebrum and optical lobes. Excluding suboesophageal ganglion, about 64 to 68 5-HT/TPH immunoreactive positive somata were observed in the brain of the first instar larvae, these somata in the brain are clustered into 10 groups and located dorsomedial protocerebrum (group1), dorsolateral protocerebrum (group2,3), anterioventral protocerebrum (group4,6), deutocerebrum (group5), optical lobes(group7-9), tritocerebrum (group10). About 108 to 126 5-HT/TPH immunoreactive positive somata were observed in the brain of the last instar larvae, two new groups were observed on the basic of 10 groups, which are localized anterioventral between protocerebrum and deutocerebrum (group11), mederal tritocerebrum (group12). About 116 to 134 5-HT/TPH immunoreactive positive somata were observed in the brain of the adult cockroach , one new group was observed on the basic of 12 groups, which is localized lateral toα-lobe(group13) . About 21 5-HT/TPH immunoreactive positive somata were observed in the suboesophageal ganglion, no difference among the first instar larvae, the last instar larvae and the adult cockroach.This article suggests that specific TPH exists in the insects, which is responsible for the product of 5-HT in the central nervous system.The role of serotonin during development in the insect is discussed in this article, it suggests that serotonin is not as a neurotransmitter and a neuromodulator throughout the larval stage, but also as a signaling molecule which guiding the neuronal morphogenesis and migration, differentiation. The results and analyses offers academic foundation to the research concerning the physiological mechanism of insect nervous system, also accumulates scientific information for clarifying the role of serotonin and tryptophan hydroxylase throughout the development in the insects.