Strain difference in fear between spontaneously hypertensive and normotensive rats is mediated by adrenal cortical hormones

In the present study we sought to determine whether the strain difference in fear reactivity between spontaneously hypertensive rats (SHR) and strain-matched WKY controls might be related to adrenocortical function. SHR and WKY were subjected to adrenalectomy prior to classical fear conditioning. Adrenal cortical steroids were replaced in some animals. Adrenalectomy produced comparable effects on conditioned fear reactivity in SHR and WKY and steroid replacement reversed the effects of adrenalectomy in both strains. However, a larger dose was required to compensate for adrenalectomy in SHR. These date implicate functions related, directly or indirectly, to the adrenal cortex, in the maintenance of the strain difference in fear reactivity.