Changes of open field behavior in animal model of depression.

Animal model of depression was developed by means of chronic exposure of rat pups to anticholinergic drugs (Atropine, Scopolamine) during the early life period from postnatal day 7 (P7) and/or 14 (P14) to P21 and/or P28, respectively. Such procedure resulted in lasting behavioral changes that were evident long after drug discontinuation and persisted at mature age (2-3 month period). Behavioral changes included most indices of open field behavior. Modeled animals exhibited significant depression of locomotor activity certified by sharp reduction of the number of crossed squares, rising of a head and vertical standings. Grooming behavior was also significantly decreased. Frequency of center entrance and the time of staying in the center of open field were sharply shortened. Modeled animals exhibited complete loss of exploratory motivation which wasn't related to the enhancement of fear emotion so far as values of incidence of urination and defecation remained unchangeable. These findings indicate that postnatal exposure of rat pups to Atropine and/or Scopolamine induces lasting behavioral "despai"' or "refractory loss of interest" at mature age. In sum animal model of depression which are characterized by super sensitivity of brain muscarinic cholinergic system exhibit more depressed behavioral items in open field than other types of animal models of depression. These data imply the preference of muscarinic cholinergic super sensitivity for the development of depressive state and therefore they are very significant for both basic science and clinical research issues.