PHARMACOLOGICAL MANIPULATION OF HUMAN GASTROINTESTINAL BLOOD-FLOW

The splanchnic circulation is one of the largest vascular regions in m an. In the past, this has been difficult to study because of methodolo gical problems. The adapting of noninvasive Doppler techniques has mad e it possible to develop reproducible measurements of coeliac and supe rior mesenteric artery blood flow, which are the main contributors to the gastrointestinal vasculature. This has resulted in the further und erstanding of neurogenic and humoral control of this region in a numbe r of physiological and pathophysiological states, and has contributed towards the knowledge of its pharmacological control. These studies ar e of relevance to cardiovascular homeostasis and, in particular, syste mic blood pressure control which depends upon various factors includin g responses in different vascular regions. In this review the key phys iological factors which influence pharmacological studies on this circ ulation will be discussed. Examples will be provided, in subjects with cardiovascular and neurological disorders, of how administration of e ndogenous and exogenous substances, including drugs with specific phar macological effects, alter human gastrointestinal blood flow. These wi ll include insulin, alcohol, the somatostatin analogue octreotide, the central acting sympatholytic clonidine and the angiotensin II-convert ing inhibitor captopril. The relevance of these studies to subjects wi th postural hypotension due to sympathetic denervation and to primary hypertension. in particular, will be discussed.