Airpuff Startle Stress Elicited Fos Expression in Brain Cardiovascular Areas of Young Shr and Wky Rats

Prior studies comparing Fos expression in adult Wistar Kyoto (WKY) and Spontaneously Hypertensive rats (SHR) identified more Fos-positive neurons in a subset of brain regions following two stressors: placement in a startle chamber and presentation of an airpuff startle stimulus. The present study assessed Fos expression in five week old SHR and WKY rats in those same brain areas. Like adults, young SHR expressed more Fos-positive neurons than WKY in response to the startle chamber alone. Unlike adults, in the SHR only the locus coeruleus showed a increases in Fos expression following addition of the airpuff. Otherwise, startle chamber and airpuff startle treatments induced roughly equivalent Fos expression in the SHR, possibly reflecting a ceiling effect. Young WKY exhibited predominant airpuff-induced elevations. The present results demonstrate that certain brain regions are strain-differentially activated by stressors prior to overt hypertension and that differential Fos expression is an early developmental feature of these strains.