title: Anhedonia but not passive floating is an indicator of depressive-like behavior in two chronic stress paradigms.
abstract: Depression is the most common form of mental disability in the world. Depressive episodes may be precipitated by severe acute stressful events or by mild chronic stressors. Studies on the mechanisms of depression require both appropriate experimental models (most of them based on the exposure of animals to chronic stressors), and appropriate tests for assessment of depressive states. In this study male Wistar rats were exposed to two different chronic stress paradigms: an eight-week chronic unpredictable mild stress or a two-week combined chronic stress. The behavioral effects of stress were evaluated using sucrose preference, forced swim and open field tests. After the exposure to chronic unpredictable mild stress, anhedonia was developed, activity in the open field increased, while no changes in the duration of passive floating could be detected. After chronic combined stress, anhedonia was also evident, whereas behavior in the open field and forced swim test did not change. The levels of corticosterone in the blood and brain structures involved in stress-response did not differ from control in both experiments. The absence of significant changes in corticosterone levels and passive floating may be indicative of the adaptation of animals to chronic stress. Anhedonia appears to be a more sensitive indicator of depressive-like behavioral effects of chronic stress as compared to behavior in the forced swim or open field tests.
authors.affiliation: Laboratory of Functional Biochemistry of the Nervous System, Institute of Higher Nervous Activity and Neurophysiology, Russian Academy of Sciences, Moscow, Russia; mikhail_stepanichev@yahoo.com.
authors.forename: Mikhail Yu
authors.initials: MY
authors.lastname: Stepanichev
authors.affiliation: Laboratory of Functional Biochemistry of the Nervous System, Institute of Higher Nervous Activity and Neurophysiology, Russian Academy of Sciences, Moscow, Russia.
authors.forename: Anna O
authors.initials: AO
authors.lastname: Tishkina
authors.affiliation: Laboratory of Functional Biochemistry of the Nervous System, Institute of Higher Nervous Activity and Neurophysiology, Russian Academy of Sciences, Moscow, Russia.
authors.forename: Margarita R
authors.initials: MR
authors.lastname: Novikova
authors.affiliation: Laboratory of Functional Biochemistry of the Nervous System, Institute of Higher Nervous Activity and Neurophysiology, Russian Academy of Sciences, Moscow, Russia.
authors.forename: Irina P
authors.initials: IP
authors.lastname: Levshina
authors.affiliation: Laboratory of Functional Biochemistry of the Nervous System, Institute of Higher Nervous Activity and Neurophysiology, Russian Academy of Sciences, Moscow, Russia.
authors.forename: Sofiya V
authors.initials: SV
authors.lastname: Freiman
authors.affiliation: Laboratory of Functional Biochemistry of the Nervous System, Institute of Higher Nervous Activity and Neurophysiology, Russian Academy of Sciences, Moscow, Russia.
authors.forename: Mikhail V
authors.initials: MV
authors.lastname: Onufriev
authors.affiliation: Laboratory of Functional Biochemistry of the Nervous System, Institute of Higher Nervous Activity and Neurophysiology, Russian Academy of Sciences, Moscow, Russia.
authors.forename: Olga A
authors.initials: OA
authors.lastname: Levchenko
authors.affiliation: Laboratory of Functional Biochemistry of the Nervous System, Institute of Higher Nervous Activity and Neurophysiology, Russian Academy of Sciences, Moscow, Russia.
authors.forename: Natalia A
authors.initials: NA
authors.lastname: Lazareva
authors.affiliation: Laboratory of Functional Biochemistry of the Nervous System, Institute of Higher Nervous Activity and Neurophysiology, Russian Academy of Sciences, Moscow, Russia.
authors.forename: Natalia V
authors.initials: NV
authors.lastname: Gulyaeva
mesh_terms: D000818:Animals; D001921:Brain / Q000378:metabolism; D003345:Corticosterone / Q000378:metabolism; D003863:Depression / Q000097:blood / Q000209:etiology* / Q000473:pathology / Q000503:physiopathology*; D004195:Disease Models, Animal; D004597:Electroshock / Q000009:adverse effects*; D005106:Exploratory Behavior; D005518:Food Preferences; D008124:Locomotion; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D012934:Social Isolation / Q000523:psychology*; D013395:Sucrose / Q000008:administration & dosage; D013550:Swimming / Q000523:psychology; D013997:Time Factors
chemical_list: D013395:Sucrose; D003345:Corticosterone