Differential startle amplitude and corticosterone response in rats

Area of Science:

• Neuroendocrinology
• Behavioral Neuroscience
• Immunology

Background:

• Hypothalamic-pituitary-adrenal (HPA) axis activity varies significantly across rat strains.
• This variation influences susceptibility to autoimmune diseases.
• Behavioral correlates of these neuroendocrine differences require further characterization.

Purpose of the Study:

• To compare acoustic (ASR) and tactile (TSR) startle responses.
• To assess corticosterone response to acoustic startle stimuli.
• To investigate behavioral correlates of HPA axis differences in rat strains.

Main Methods:

• Comparison of ASR and TSR amplitudes in Lewis (LEW/N), Fischer (F344/N), and Sprague-Dawley (SD) rats.
• Assessment of ASR habituation across strains.
• Measurement of corticosterone levels before and after acoustic startle stimuli exposure.

Main Results:

• LEW/N rats displayed larger ASR and TSR compared to F344/N rats; SD rats were intermediate.
• ASR habituation occurred similarly in LEW/N and F344/N rats, but not in SD rats.
• Acoustic startle stimuli elevated corticosterone in F344/N and SD rats, but not LEW/N rats.

Conclusions:

• An inverse relationship exists between acoustic startle response amplitude and HPA axis activation across rat strains.
• This inverse relationship was supported by a negative correlation between corticosterone and ASR amplitude within the F344/N strain.
• Neuroendocrine differences influence behavioral responses to stress and may impact autoimmune disease susceptibility.