Effects of Intracarotid Injections of Hypertonic Solutions on Arterial Pressure in the Rabbit

The intracarotid injection of hypertonic saline in the rabbit induces a brief drop in arterial pressure followed by a somewhat longer pressor phase. The “osmoreceptors” activating these changes are related to the hindbrain and are not the elements responsible for releasing neurohypophysial hormones. The pressure changes are not prevented by vagotomy, deafferentation of the carotid body and sinus, adrenalectomy, or parasympathetic blockade. The blood pressure effects are interpreted as resulting from sequential inhibition and stimulation of medullary vasomotor centers by the hypertonic solutions.