Effect of neuropeptides ACTH(4-7)-Pro-Gly-Pro and ACTH(6-9)-Pro-Gly-Pro on behavior of laboratory animals and serum BDNF under hypothyroidism

Objective. To study the effect of neuropeptides ACTH(4-7)-Pro-Gly-Pro and ACTH(6-9)-Pro-Gly-Pro on behavior of laboratory animals and serum brain-derived neurotrophic factor (BDNF) under experimental hypothyroidism. Material and methods. The experiment was performed on male rats divided into 4 groups: group 1 — intact animals (control); group 2 — animals with induced hypothyroidism; groups 3 and 4 — animals treated with ACTH(4-7)-Pro-Gly-Pro and ACTH(6-9)-Pro-Gly-Pro under experimental hypothyroidism, respectively. Thyroid hypofunction in laboratory animals was induced by mercazolil 5 mg/kg administered to the stomach through a tube. Mercazolil was dissolved in water and administered daily for 42 days. We assessed behavioral activity of rats using the Elevated Cruciate Maze test. Serum BDNF was analyzed by enzyme-linked immunosorbent assay using a Multiscan FC immunoassay and highly sensitive ELISA kits. Results. Under experimental hypothyroidism, the Elevated Cruciate Maze test revealed decrease in motor and exploratory activity (decreased number of entries into open hoses, exits to central zone, time spent in open hoses and center of labyrinth, racks, increased number of entries into closed hoses) and increased anxiety (acts of short-term grooming, number of ‘peeps’ from closed sleeves and freezing time). In addition, serum BDNF decreased under thyroid hypofunction. Under experimental hypothyroidism, peptide substances contributed to correction of behavioral disorders, anxiety-depressive state and recovery of serum BDNF. Conclusion. Regulatory peptides ACTH(4-7)-Pro-Gly-Pro and ACTH(6-9)-Pro-Gly-Pro under experimental hypothyroidism are characterized by pleiotropic effect with psychomodulatory, anxiolytic and neurotrophic activity.