Biology Reference
In-Depth Information
they can change the intrinsic properties of cells, altering their sensitivi-
ties to inputs from other neurons. Insect biogenic amines are octopa-
mine, tyramine, serotonin, and dopamine. Insect and human brains
share serotonin and dopamine as important neuromodulators. Bio-
genic amines (also called bioamines) act by binding to proteins called
receptors that are located on the surfaces of cells. h ere are many dif-
ferent receptors associated with the same bioamines that result in dif-
ferent consequences to the cells. Some bioamines cross-talk with (bind
to) the receptors of others. When the bioamine binds to the receptor, it
initiates an intracellular signaling cascade that involves so-called sec-
ond messenger compounds, such as cyclic adenosine monophosphate
(cAMP), cyclic guanosine monophosphate (cGMP), and protein kinases,
such as cAMP-dependent protein kinase (PKA), calcium phosopholipid-
dependent protein kinase (PKC), and cGMP-dependent protein kinase
(PKG), that are activated and af ect changes in other downstream sig-
nal molecules. It is obvious that the potential complexity of neural
networks involved in behavior is enormous, with 900,000 neurons con-
nected in complex ways involving multiple synapses and modulated by
multiple bioamines, receptors, and cross-talking signal-transduction
pathways.
We chose to look at a very tiny subset of the possible complexity of
neurobiochemical pathways, namely, those that have been shown to be
involved in sucrose sensory perception, motor activity, and learning
and memory. Octopamine and tyramine, when fed to bees or injected
into the thorax, increase responsiveness to sucrose. Dopamine de-
creases responsiveness when injected. Serotonin has no ef ect on su-
crose response but does af ect motor activity of the antennae. Dave
Schulz, at the time a graduate student in the laboratory of Gene Rob-
inson, looked at titers of the biogenic amines octopamine, dopamine,
and serotonin in brains of high- and low-strain bees. He separated the
brain into major regions rel ecting dif erent aggregations of neuropils.
He looked at bees that were 1 day and 12 days old. Our expectation
was that because high-strain bees are more responsive to sucrose as
new adults, newly emerged and throughout life, they would have
higher brain titers of octopamine and lower titers of dopamine. Be-
