Epinastine Hydrochloride

Aminergic neurons mediate reward signals in mammals and insects. In crickets, we showed that blockade of synaptic transmission from octopamine neurons (OANs) impairs conditioning of an odor (conditioned stimulus, CS) with water or sucrose (unconditioned stimulus, US) and execution of a conditioned response (CR) to the CS. It has not yet been established, however, whether findings in crickets can be applied to other species of insects. In this study, we investigated the roles of OANs in conditioning of salivation, monitored by activities of salivary neurons, and in execution of the CR in cockroaches (Periplaneta americana). We showed that injection of epinastine (an OA receptor antagonist) into the head hemolymph impaired both conditioning and execution of the CR, in accordance with findings in crickets. Moreover, local injection of epinastine into the vertical lobes of the mushroom body (MB), the center for associative learning and control of the CR, impaired execution of the CR, whereas injection of epinastine into the calyces of the MB or the antennal lobes (primary olfactory centers) did not. We propose that OANs in the MB vertical lobes play critical roles in the execution of the CR in cockroaches. This is analogous to the fact that midbrain dopamine neurons govern execution of learned actions in mammals.

Visual-orientation learning of a tethered flying bee was investigated using a flight simulator and a novel protocol in which orientation preference toward trained visual targets was assessed in tests performed before and after appetitive conditioning. Either a blue or a green rectangle (conditioned stimulus, CS) was associated with 30% sucrose solution (unconditioned stimulus, US), whereas the other rectangle was not paired with US. Bees were tested in a closed-looped flight simulator 5 min after ten pairings of the US and CS. Conditioned bees were preferentially oriented to the CS after such training. This increase in preference for CS was maintained for 24 h, indicating the presence of long-term memory. Because the total orienting time was not altered by conditioning, conditioning did not enhance orientation activity itself but increased the relative time for orientation to CS. When 0.4 or 4 mM epinastine (an antagonist of octopamine receptors) was injected into the bee's head 30 min prior to the experiment, both short- and long-term memory formation were significantly impaired, suggesting that octopamine, which is crucial for appetitive olfactory learning in insects, is also involved in visual orientation learning.