A comparison of hypotensive and non-hypotensive hemorrhage on Fos expression in spinally projecting neurons of the paraventricular nucleus and rostral ventrolateral medulla

Abstract

The protein, Fos, detected immunohistochemically, was used to identify neurons in the brain that were activated after hemorrhage in the conscious rat. Spinally projecting neurons in the paraventricular nucleus (PVN) and rostral ventrolateral medulla (RVLM) were identified by the presence of rhodamine-labeled latex beads which had been previously injected into the upper thoracic spinal cord. On the experimental day, conscious rats underwent either (1) withdrawal of 4 ml of blood from a carotid cannula (n = 8) which reduced mean arterial pressure from 96.6 ± 2.7 to 42.7 ± 7.1 mmHg, (2) withdrayl of 2 ml of blood (n = 4) which did not affect mean arterial pressure. Animals that were not hemorrh..