Hypophysial portal blood flow during preganglionic stimulation of the superior cervical ganglion under condition of systemic arterial blood pressure stabilization in rat.

ABSTRACT

The presence of hypothalamic hormones in the pituitary portal blood is regarded as the principal factor by which the hypothalamus controls pituitary secretion. In contrast to numerous investigations on hypothalamic hormone release, the regulation of the hypophysial-portal blood flow (HPBF) has been scarcely studied. Hypophysial-portal vessels were exposed according to the Worthington's method [1966]. The 10-min blood samples were collected before and during unilateral or alternative bilateral electrical stimulation of the preganglionic fibers of the superior cervical ganglia (SCG). During blood samples collection the stable systemic arterial blood pressure was maintained by a barostat. The HPBF was estimated according to the determination of the hemoglobin in samples of washed and collected blood from the cut pituitary portal vessels. The mean HPBF was 3.5 microliters/min. Electrical stimulation of SCG. did not change HPBF. This indicates that sympathetic efferents do not participate in the regulation of HPBF under conditions of stabilization of the systemic arterial blood pressure.