Effect of vasopressin on blood flow distribution in the stomach of cats with gastric ulcer

What is nausea? A historical analysis of changing views

The connotation of "nausea" has changed across several millennia. The medical term 'nausea' is derived from the classical Greek terms ναυτια and ναυσια, which designated the signs and symptoms of seasickness. In classical texts, nausea referred to a wide range of perceptions and actions, including lethargy and disengagement, headache (migraine), and anorexia, with an awareness that vomiting was imminent only when the condition was severe. However, some recent articles have limited the definition to the sensations that immediately precede emesis. Defining nausea is complicated by the fact that it has many triggers, and can build-up slowly or rapidly, such that the prodromal signs and symptoms can vary. In particular, disengagement responses referred to as the "sopite syndrome" are typically present only when emetic stimuli are moderately provocative, and do not quickly culminate in vomiting or withdrawing from the triggering event. This review considers how the definition of "nausea" has evolved over time, and summarizes the physiological changes that occur prior to vomiting that may be indicative of nausea. Also described are differences in the perception of nausea, as well as the accompanying physiological responses, that occur with varying stimuli. This information is synthesized to provide an operational definition of nausea.

Physiological basis and pharmacology of motion sickness: an update

Motion sickness can occur when sensory inputs regarding body position in space are contradictory or are different from those predicted from experience. Signals from the vestibular system are essential for triggering motion sickness. The evolutionary significance of this malady is unclear, although it may simply represent the aberrant activation of vestibuloautonomic pathways that typically subserve homeostasis. The neural pathways that produce nausea and vomiting during motion sickness are presumed to be similar to those that generate illness after ingestion of toxins. The neural substrate of nausea is unknown but may include neurons in the hypothalamus and inferior frontal gyrus of the cerebral cortex. The principal motor act of vomiting is accomplished through the simultaneous contractions of inspiratory and expiratory respiratory muscles and is mediated by neurons in the lateral medullary reticular formation and perhaps by cells near the medullary midline. Cocontraction of the diaphragm and abdominal muscles increases pressure on the stomach, which causes gastric contents to be ejected through the mouth. Effective drugs for combating motion sickness include antihistamines, antimuscarinics, 5-HT1A (serotonergic) receptor agonists and neurokinin type 1 receptor antagonists. However, considerable information concerning the physiological basis and pharmacology of motion sickness is unknown; future research using animal models will be required to understand this condition.