Octopamine and serotonin influence on corpora allata activity in honey bee ( Apis mellifera) larvae

Abstract

Effects of biogenic amines on the corpora allata of honey bee worker larvae ( Apis mellifera) were studied in late larval development. Under in vitro conditions, octopamine and serotonin caused a dose-dependent stimulation of juvenile hormone release and increased intraglandular contents of juvenile hormone and its precursor methyl famesoate in prepupal glands. The octopamine analog synephrine was as potent as octopamine and serotonin, whereas dopamine and noradrenaline were ineffective. Octopamine- and serotonin-evoked responses were blocked by mianserin, ketanserin, and by the α-adrenergic receptor antagonist phentolamine. Gland activity was also increased by the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (IBMX) and the adenylate cyclase activator forskolin, the effects of the two agents being additive. IBMX in the presence of a threshold concentration of octopamine (10 −8 M) caused a potentiation of the octopamine effect on juvenile hormone release, indicating that the action of the biogenic amine is mediated by cAMP. Octopamine-induced increase in juvenile hormone production could not be reversed by washing out the biogenic amine, suggesting a longterm irreversible effect directly on corpora allata cells, possibly via cAMP. Accordingly, biogenic amines, in particular octopamine and serotonin, have to be considered as involved in the regulation of corpora allata activity during caste development of honey bees.