Abstract <p>The aim of the study was to investigate the functional roleof the TAAR1 receptor in the formation of the behavioral componentof the stress response. The behavior of TAAR1 knockout (TAAR1-KO) miceand wild-type (WT) mice was assessed in anxiety tests—the elevatedzero maze (EZM) and novelty-induced hypophagia test (NIHT, hyponeophagia),as well as in the acoustic startle reflex (ASR) test. Testing wasperformed before and after chronic stress (predator odor/stressmodel), and also 1.5 months after its cessation to assess long-termbehavioral changes. In the EZM test, no significant differencesin anxiety levels between TAAR1-KO and WT groups were found eitherunder normal conditions or after stress exposure. However, the stressresponse dynamics differed between them. In the NSFT, TAAR1-KO miceinitially demonstrated motor hyperactivity in response to the novelenvironment, leading to a sharp decrease in the latency to approachthe food, while having no effect on other anxiety scores in thistest. Six weeks after the cessation of the stress exposure, anxietyscores continued to increase in mice of both groups. Unlike WT mice, TAAR1-KOmice exhibited specific hyperactivity during the early stages ofthe EZM and NSFT tests. In the ASR test, there were no intergroupdifferences before stress. After stress exposure, its impact onthe ASR amplitude was more pronounced in TAAR1-KO mice. Conclusions:the TAAR1 receptor plays an important role in modulating the behavioral responseto chronic stress, influencing its developmental dynamics and long-termconsequences. TAAR1 knockout leads to specific hyperactivity in stressogenicsituations and increases the sensitivity of sensorimotor responsesto stress.</p>