posted on 2020-01-08, 23:44authored byMarcel Pratavieira, Anally Ribeiro da Silva Menegasso, Thaisa Roat, Osmar Malaspina, Mario Sergio Palma
The proboscis extension
response (PER) reflex may be used to condition the pairing of an odor with sucrose, which
is applied to the antennae, in experiments to induce learning, where
the odor represents a conditioned stimulus, while sucrose represents
an unconditioned stimulus. A series of studies have been conducted
on honeybees, relating learning and memory acquisition/retrieval using
the PER as a strategy for accessing their ability to exhibit an unconditioned
stimulus; however, the major metabolic processes involved in the PER
are not well known. Thus, the aim of this investigation is profiling
the metabolome of the honeybee brain involved in the PER. In this
study, a semiquantitative approach of matrix-assisted laser desorption
ionization (MALDI) mass spectral imaging (MSI) was used to profile
the most abundant metabolites of the honeybee brain that support the
PER. It was reported that execution of the PER requires the metabolic
transformations of arginine, ornithine, and lysine as substrates for
the production of putrescine, cadaverine, spermine, spermidine, 1,3-diaminopropane,
and γ-aminobutyric acid (GABA). Considering the global metabolome
of the brain of honeybee workers, the PER requires the consumption
of large amounts of cadaverine and 1,3-diaminopropane, in parallel
with the biosynthesis of high amounts of spermine, spermidine, and
ornithine. To exhibit the PER, the brain of honeybee workers processes
the conversion of l-arginine and l-lysine through
the polyamine pathway, with different regional metabolomic profiles
at the individual neuropil level. The outcomes of this study using
this metabolic route as a reference are indicating that the antennal
lobes and the calices (medial and lateral) were the most active brain
regions for supporting the PER.