Since cerebral vasoconstriction alone may impair the hypothalamic and pituitary circulation, we planned to investigate whether the hormonal response to the vasoconstriction that may be induced by the head injury is a significant component of the general acute hormonal response to head injury. Although diffuse adrenocorticotropic hormone immunohistochemical staining of the adenohypophysis of rabbits was observed in the head trauma administered group, only mild positive staining was present in the Endothelin-1 administered group. However, decreased prolactin staining was found in both of the groups. It is postulated that trauma induced vasoconstriction may not be an important manipulating factor in the corticotrophic hormone response to injury, while it may be responsible for the decreased prolactin response. (C) 2002 Elsevier Science Ltd. All rights reserved.