Distribution of SPR-like immunoreactivity in the medullary visceral zone of the rat and changes following acute myocardial ischemia induced by intravenous injection of vasopressin.

Abstract

Substance P receptor-like immunoreactive (SPR-LI) structures and changes following intravenous injection of vasopressin in the medullary visceral zone (MVZ) of the rat were studied by using immunohistochemical methods. In normal control rats the distribution of SPR-LI structure in MVZ generally matched with that of immunostaining against substance P (SP-LI) except in some areas. SPR-LI neurons and dendrites differed in size and shape in different areas of MVZ. Their dendrites could be classified into three types, i.e, wool-shaped, smooth and varicose. Some SPR-LI neurons were also positive for tyrosine hydroxylase-like immunoreactivity (TH-LI) . After administration of vasopressin SPR-LI structures became denser, especially at levels of pyramidal decussation (PYX) and area postrema (AP). The dendrites of motor dorsal nucleus of X (NMDX) in the dorsal part of MVZ appeared thin and straight in morphology instead of curl and thick outlooks. These results implicate that some SPR-LI neurons might be involved in the modulation of the cardiovascular stress induced by vasopressin.