Induction of Fos-like immunoreactivity in the hypothalamic, medullary and thoracic spinal cord neurons following middle cerebral artery occlusion in rats

This study is a sequel of our previous work which demonstrated the expression of Fos-like immunoreactivity (Fos-LI) in the spinal cord motoneurons of rat following permanent occlusion of the middle cerebral artery (MCA). We report here Fos-LI in the hypothalamic, medullary and thoracic spinal cord neurons some of them are believed to be involved in cardiovascular regulation after the cerebral ischaemic insult. At 1 and 2 h, especially in the latter after right sided MCA occlusion, Fos-LI confined to the cell nucleus, was detected bilaterally in cells of the supraoptic nucleus (SON) and the paraventricular nucleus (PVN) of the hypothalamus, the nucleus of the solitary tract (NTS), the area postrema and ventrolateral medulla (VLM). A few Fos-like immunoreactive neurons were observed in the nucleus raphe pallidus and obscurus, and in the intermediolateral nucleus of the thoracic spinal cord. In the corresponding areas in sham-operated animals, Fos-like immunoreactive neurons were sparsely distributed or absent. Colocalization study showed that a variable number of the Fos-like immunoreactive neurons in NTS and VLM coexpressed tyrosine-hydroxylase (TH) immunoreactivity. Such double labelled neurons appeared to be more common in the latter. It is suggested that the induction of Fos-LI in neurons of the hypothalamus, medulla and thoracic spinal cord was linked to cardiovascular regulation following the middle cerebral artery occlusion. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.