The frontal ganglionic system: Cauterization effects on serotonin circadian rhythms of the cockroach corpora allata and corpora cardiaca

Abstract

We report that the levels of serotonin and its metabolite 5-hydroxyindoleacetic acid (5-HIAA) in the corpora allata (CA) and the corpora cardiaca (CC) of an insect show circadian rhythms. During the 24 h day, the levels of 5-HT and its immediate metabolite 5-HIAA were maximal at 24.00 h and minimal at 12.00 h. The effects of cauterization of the frontal ganglionic system on the circadian rhythms of 5-HT and 5-HIAA levels of CA and CC were studied. The removal of the frontal ganglion (FG) leads to abolition of circadian rhythms of 5-HT and 5-HIAA shown by cockroach CA and CC. Furthermore, the cauterization of both frontal connectives that connect the FG to the tritocerebral lobes leads to abolition of 5-HT and 5-HIAA rhythms of cockroach CA and CC. The cauterization of nervus connectivus that connects the FG with the protocerebrum also leads to abolition of circadian rhythms of 5-HT and 5-HIAA levels. The connections of the brain with the FG are found in the present investigation therefore to be important for persistence of circadian rhythms of 5-HT and 5-HIAA levels in the CA and the CC. © 1992.