Effects of Acute Administration of Adipokinetic Hormone on Depression, Anxiety, Pain, Locomotion and Memory in Mice.

The neurosecretory cells in the corpus cardiacum of insects synthesize a set of hormones that are called adipokinetic, hypertrehalosemic or hyperprolinemic depending on the insect in question. They are the Adipokinetic Hormone/Red Pigment-Concentrating Hormone (AKH/RPCH) family of peptides. The present study investigated the effects of acute administration of Locusta Migratoria (Locmi-AKHII) and Anax Imperator (Anaim-AKH) on depression, anxiety, pain (analgesy), locomotion and memory in mice in forced swimming (FST), elevated plus maze (EPM), hot plate, locomotor activity and passive avoidance tests. Both Locmi-AKH-II (4 mg/kg) and Anaim-AKH (0.25 and 0.50 mg/kg) decreased immobility time (in sec, s) in the FST test. Anaim-AKH (0.5 and 1 mg/kg) increased the percentage of time spent in open arms/total time spent and the percentage of the number of open arm/total arm entries in the EPM test. Anaim-AKH (1 and 2 mg/kg) significantly increased latency (s) (initial time passed) for mice to lick their hind paws or jumping in the hot plate test. Anaim-AKH (4 mg/kg) significantly decreased the total distance (cm) moved, or the speed (cm/s) of movement of the animals in the locomotor activity test. Neither Locmi-AKH-II nor Anaim-AKH altered the retention latency (s) in the passive avoidance test. Both Locmi-AKH-II and Anaim-AKH exerted antidepressant effects, while only Anaim-AKH had anxiolytic and analgesic effects when administered acutely. Anaim-AKH diminished locomotion at higher doses while Locmi-AKH-II had no such effects. Neither Locmi-AKH-II nor Anaim-AKH disturbed learning and memory when acutely administered. Data of our studies suggest clinical potentials of AKH to be used in depression, anxiety and pain without disturbing memory.