Neurohumoral Control of Gut Mucosal Defense

Systemic blood pressure (BP) is the product of cardiac output and total peripheral resistance. Cardiac output is controlled by the heart rate, myocardial contractility, preload, and afterload. Vascular resistance (vascular hindrance × viscosity) is under local autoregulation and general neurohumoral control through sympathetic adrenergic innervation and circulating catecholamines. Sympathetic innovation predominates in organs receivingflowin excess of their metabolic demands (skin, splanchnic organs, kidney), while innervation is poor and autoregulation predominates in the brain and heart. The distribution of blood flow depends on the relative resistances of the organ circulations. During stress (hypoxia, low cardiac output), a raise in adrenergic tone and in circulating catecholamines leads to preferential vasoconstriction in highly innervated organs, so that blood flow is directed to the brain and heart. Catecholamines also control the levels of the vasoconstrictors renin, angiotensin II, and vasopressin. These general principles also apply to the neonate.

Download Full-text

Neurohumoral control of colonic motility in the rabbit

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.1983.245.4.g582 ◽

1983 ◽

Vol 245 (4) ◽

pp. G582-G588 ◽

Cited By ~ 1

Author(s):

W. J. Snape ◽

S. Shiff

Keyword(s):

Contractile Activity ◽

Control Period ◽

Colonic Motility ◽

Distal Colon ◽

Proximal Colon ◽

Base Line ◽

Cholinergic Stimulation ◽

Bipolar Electrodes ◽

Neurohumoral Control ◽

Alpha Adrenergic Agonist

Colonic motility was examined in the proximal (taeniated) and distal (nontaeniated) colon of New Zealand White rabbits. Colonic myoelectric and contractile activities were recorded by bipolar electrodes and extraluminal strain gauges sewn on the antimesenteric serosal surface of the proximal and distal colon. Slow-wave frequency consistently was slower in the proximal colon (13.2 +/- 0.9) compared with the distal colon (15.8 +/- 1.2) (P less than 0.05). During the control period 81.8 +/- 5.2% of slow waves have superimposed spike potentials in the proximal colon. The distal colon had similar amounts of spike activity. The distal colon had increased base-line contractility (P less than 0.02). Atropine inhibited spike and contractile activity on both sides of the colon, but the distal colon still had more contractile activity than the proximal colon (P less than 0.02). The alpha-adrenergic agonist phenylephrine and antagonist phentolamine had no effect on colonic motility. Isoproterenol inhibited colonic smooth muscle spike and contractile activity. This effect was blocked by propranolol. Administration of trimethaphan camsylate caused an increase in spike and contractile activity only in the distal colon. The effect of trimethaphan on the distal colon was inhibited by atropine. These studies show that 1) tonic cholinergic stimulation exists both in the proximal and in the distal colon, 2) circulating catecholamines have minimal effect on base-line colonic motility, and 3) tonic nonadrenergic inhibition of the distal colon modulates the tonic cholinergic stimulation.

Download Full-text