An animal’s internal state is a critical parameter required for adaptation to
a given environment. An important aspect of an animal’s internal state is the
energy state that is adjusted to the needs of an animal by energy homeostasis.
Glucose is one essential source of energy, especially for the brain. A
shortage of glucose therefore triggers a complex response to restore the
animal’s glucose supply. This counter-regulatory response to a glucose deficit
includes metabolic responses like the mobilization of glucose from internal
glucose stores and behavioral responses like increased foraging and a rapid
intake of food. In mammals, the catecholamines adrenalin and noradrenalin take
part in mediating these counter-regulatory responses to a glucose deficit. One
candidate molecule that might play a role in these processes in insects is
octopamine (OA). It is an invertebrate biogenic amine and has been suggested
to derive from an ancestral pathway shared with adrenalin and noradrenalin.
Thus, it could be hypothesized that OA plays a role in the insect’s counter-
regulatory response to a glucose deficit. Here we tested this hypothesis in
the honeybee (Apis mellifera), an insect that, as an adult, mainly feeds on
carbohydrates and uses these as its main source of energy. We investigated
alterations of the hemolymph glucose concentration, survival, and feeding
behavior after starvation and examined the impact of OA on these processes in
pharmacological experiments. We demonstrate an involvement of OA in these
three processes in honeybees and conclude there is an involvement of OA in
regulating a bee’s metabolic, physiological, and behavioral response following
a phase of prolonged glucose deficit. Thus, OA in honeybees acts similarly to
adrenalin and noradrenalin in mammals in regulating an animal’s counter-
regulatory response