Vascular reactivity of human internal mammary and gastroepiploic arteries

The Right Gastroepiploic Artery Graft for Coronary Artery Bypass Grafting: A 30-Year Experience

Throughout its 30-year history, the right gastroepiploic artery (GEA) has been useful for in situ grafts in coronary artery bypass grafting (CABG). The early graft patency rate is high, and the late patency rate has improved by using the skeletonized GEA graft and proper target selection, which involves having a target coronary artery with a tight >90% stenosis. Total arterial revascularization with the internal thoracic artery and GEA grafts is an option for achieving better outcomes from CABG procedures.

Gastroepiploic artery graft in coronary artery bypass grafting

The right gastroepiploic artery (GEA) has been recognized as a suitable and reliable conduit for coronary bypass surgery. From a sizable number of experiences, we know the use of this artery does not increase surgical risk, and no gastric ischemia nor abdominal complications occur with takedown of the GEA. This artery undergoes less significant arteriosclerosis and demonstrates physiological adaptability as seen in the internal thoracic artery (ITA). From our experience with over 1,500 GEA grafts, the operative mortality was 1.26%, and 5-, 10-, and 15-year survival rates were 91.7%, 81.4%, and 71.3% respectively, while the cardiac death-free survival rates were 95.8%, 91.7%, and 88.6%, respectively. The cumulative patency rate of the GEA graft was 98.5% at 1 month, 93.7% at 1 year, 86.2% at 5 years, and 70.2% at 10 years. The GEA graft is a safe and effective arterial conduit for coronary artery bypass grafting (CABG).

Anesthetic management of a patient undergoing liver transplantation who had previous coronary artery bypass grafting using an in situ right gastroepiploic artery

We describe successful anesthetic management during living-donor liver transplantation in a 63-year-old man with previous coronary artery bypass grafting (CABG) that employed an in situ right gastroepiploic artery (RGEA). Anesthesia was maintained with 1.5% isoflurane in air/oxygen and fentanyl. A five-lead electrocardiogram, transesophageal echocardiogram, and pacing pulmonary artery catheter evaluated cardiac function. A pacing wire was inserted through the catheter to prepare for intraoperative severe bradyarrhythmia. Olprinone and nicorandil were continuously infused to prevent decrease in coronary arterial blood flow and the collapse of cardiac function. Avoiding disruption of circulation to coronary arteries through injury or spasm of the RGEA graft and preparing for cardiac insufficiency during liver transplantation of a patient with previous CABG using an in situ RGEA is critical.

Cirrhosis of the liver and receptor-mediated function in vascular smooth muscle

Altered regulation of receptors on the vascular smooth muscle has been proposed as one of the mechanisms that may account for the vascular abnormalities in patients with cirrhosis of the liver. Impaired contractility and down-regulation of contractile receptors have been demonstrated in cirrhotic patients and animal models, although interpretation of the literature is hampered by methodological variation and conflicting results. There is little evidence, however, that receptor down-regulation is the cause of contractile dysfunction in either patients or animal models. Receptor desensitisation may contribute to impaired contraction in human arteries, but further investigation is required to confirm this possibility.

Interaction between thromboxane A2 and 5-hydroxytryptamine in the radial artery compared to the internal thoracic artery

The aim of the present study was to investigate if the function of 5-hydroxytryptamine-1B/1D (5-HT1B/1D) receptors in human radial artery (RA) and internal thoracic artery (ITA) can be modified by thromboxane A2 (TXA2) released from the vessel wall in these two arteries that are commonly used in coronary artery bypass grafts. The 5-HT1B/1D agonist sumatriptan contracted the RA with a maximum response of 23.5+/-6.8 mN and a pD2 value of 6.6+/-0.1. The effect of sumatriptan was significantly reduced in the ITA with a maximum of 5.8+/-2.7 mN (P<.05) and a pD2 value of 6.4+/-0.2. The TXA2 receptor antagonist SQ30741 inhibited contractions to sumatriptan in the RA but not in the ITA. It is concluded that the effect mediated by 5-HT1B/1D is augmented by endogenous TXA2 in the RA.

Vasorelaxant actions of enoximone, dobutamine, and the combination on human arterial coronary bypass grafts

Enoximone (a type III-selective phosphodiesterase inhibitor) and dobutamine (a beta-receptor agonist) are positive inotropic drugs frequently used in the postoperative management of coronary bypass surgery. The purpose of this study was to characterize their relaxant effects on the human internal mammary artery (IMA) and the gastroepiploic artery (GEA) and to test the hypothesis that their combination may have greater than additive relaxant effects. In organ baths, the relaxant effects of enoximone and dobutamine were tested on rings of IMA (n = 86) precontracted with U46619 (a thromboxane A2 mimetic), norepinephrine (NE), or KCl. The relaxant effects of dobutamine and enoximone also were tested on rings of GEA (n = 42) precontracted with U46619 and NE. The effect of the combination of enoximone and dobutamine were tested on rings of IMA (n = 24) precontracted with U46619 or NE. With respect to maximal relaxations induced by papaverine (10(-4) M), enoximone (< or =10(-3) M) caused full relaxations of IMA precontracted with NE, U46619, or KCI. Dobutamine (< or =10(-3) M) caused full relaxations of IMA precontracted with NE or KCI but only 46% (95% CI, 27-65) relaxation in the rings precontracted with U46619. Similar patterns of relaxation were observed in GEA rings, with dobutamine inducing partial relaxation in GEA precontracted with U46619. The pD2 values of enoximone and dobutamine were both significantly lower in segments precontracted with U46619. The in vitro threshold relaxant concentrations were in the upper limits or over the range of therapeutic plasma concentrations. The relaxant effect of the combination was significantly more important than the theoretic additive effect in IMA contracted with U46619 or NE. Enoximone and dobutamine are potent in vitro vasodilators but exert weak relaxant effects in IMA and GEA at concentrations in the therapeutic range. There is, however, a greater than additive vasorelaxant effect of the combination, suggesting that the vasorelaxant effect of the combination, in addition to the additive inotropic effect, may be beneficial to patients undergoing coronary bypass grafting.

Reactivity of the Human Internal Mammary Artery and the Gastroepiploic Artery to Constrictor Substances

The internal mammary artery (IMA) and the gastroepiploic artery (GEA) are frequently used to construct coronary artery bypass grafts. In order to determine and to compare their contractile properties, we studied the effects of constricting agents which are liberated or infused during coronary bypass surgery. IMA and GEA were arranged as ring segments and suspended in organ baths at optimal stretch using a normalization procedure. Concentration-contraction curves to angiotensin II, norepinephrine, U-46619, endothelin-1, leukotriene C(4) and KCl were performed. The sensitivity (pD(2)) of GEA and IMA to all the agents did not differ. However, GEA developed stronger maximal contraction force than IMA to angiotensin II (P < 0.001), norepinephrine (P < 0.05), U-46619 (P = 0.06), endothelin-1 (P < 0.01), and KCl (P < 0.01), whereas leukotriene C(4) did not induce a significant contraction on GEA and IMA. The higher contractility of GEA may explain that it is more prone to spasm than IMA in the clinical setting. This study reinforces IMA as a first-choice conduit for coronary artery bypass and emphasizes the need for antispastic drugs particularly when GEA is used as bypass vessel.http://link.springer-ny.com/link/service/journals/00547/bibs/8n4p187.html</hea

Functional comparison of the human isolated femoral artery, internal mammary artery, gastroepiploic artery, and saphenous vein

Human femoral, internal mammary, and gastroepiploic arteries and saphenous veins are used as bypass grafts for coronary surgery or for reconstruction in arterial occlusive disease. We have characterized the contractile responses of these vessels to various agents that are liberated during cardiac or vascular surgery. In organ baths, U46619 (a stable thromboxane A2 mimetic), norepinephrine, endothelin-1, angiotensin II, and KCl caused concentration-dependent contractions in all vessels tested. Leukotriene C4 did not induce any contraction in the arteries, whereas a contraction was obtained in the saphenous vein rings. U46619 induced the most powerful contraction in all vessels tested. The pD2 values for each agent did not differ among the different vessels. When responses were expressed as a percentage of KCl-induced contraction, the contraction of endothelin-1 (151 ± 5%) and leukotriene C4 (43 ± 5%) was more significant on saphenous veins than on arteries. In conclusion, thromboxane A2 appears to be the most potent endogenous constricting agent on different human vascular beds. Our second finding is that saphenous veins are more sensitive to contract to leukotriene C4 and endothelin-1 than arteries. These properties may influence early and (or) long-term vein graft patency.Key words: femoral arteries, vascular reactivity, thromboxane A2, endothelin-1, leukotrienes.

Noninvasive assessment of right gastroepiploic artery graft patency using transcutaneous color Doppler echocardiography

BACKGROUND

Because the right gastroepiploic artery graft (GEA), when routed antegastrically, is situated just behind the abdominal wall, we investigated the possibility of evaluating graft patency and flow characteristics using transabdominal color Doppler echocardiography.

METHODS

The right GEA graft was evaluated in 71 patients who underwent complete arterial revascularization, 4 months (range, 2 to 17 months) postoperatively. Selective angiography of the right GEA was performed in the patients in whom the graft could not be visualized using color Doppler echocardiography.

RESULTS

Flow in the right GEA graft was detected in 65 (91.5%) of 71 patients using color Doppler echocardiography. In all visualized right GEAs, a biphasic flow pattern was observed, with higher peak velocity during systole. Mean (+/- standard deviation) peak systolic velocity was 76+/-16 cm/s. Mean (+/- standard deviation) velocity was 41+/-14 cm/s. Selective angiography of the right GEA in 5 patients in whom the graft could not be visualized using echocardiography showed four patent and functional grafts and one graft that was open but not functional ("slender sign"). One patient died before angiography could be performed. The sensitivity of noninvasive ultrasound assessment of the patency of the right GEA graft was 94% (65 of 69 patients). In this group of patients, an overall right GEA graft patency rate of 97% (69 of 71 patients) was found at mean follow-up of 4 months (range, 2 to 17 months).

CONCLUSIONS

The right GEA graft is an adequate coronary artery graft with a good short-term patency rate, and transcutaneous color Doppler echocardiography is a useful tool for evaluating its patency and flow characteristics. Selective angiography of the right GEA can be avoided in most cases and is indicated only when the graft cannot be detected using Doppler echocardiography.

Pharmacology of coronary artery bypass grafts

Spasm of arterial and venous graft conduits can occur both during harvesting and after the graft is connected. Attempts to overcome spasm during harvesting by probing or hydraulic distension can cause structural damage to the graft, which may impair short- and long-term patency. After a coronary artery bypass graft is connected, spasm can cause major problems with myocardial perfusion. To select the best pharmacologic agent to prevent or reverse vasoconstriction in a graft requires an understanding of the reactivity of that particular type of graft to vasoconstrictor and vasodilator agents. The pharmacologic reactivity of venous and arterial graft conduits has been documented through extensive studies of isolated vessels in the organ bath and of in situ grafts in the body. In this review we summarize the current state of knowledge of the reactivity of arterial and venous grafts to vasoconstrictor and vasodilator agents and describe the practical application of this knowledge in the operating room and in the postoperative period.

Gastroepiploic artery coronary bypass graft: non-invasive patency evaluation using color and duplex Doppler ultrasonography

OBJECTIVE

Color and duplex Doppler ultrasound and digital subtraction angiography were compared for the evaluation of graft patency of the gastroepiploic artery (GEA).

METHODS

In 77 observations, ultrasound and digital subtraction angiography were compared. The coronary resistance index (cRI) was defined as the maximal systolic flow velocity minus the maximal diastolic flow velocity, divided by the maximal systolic flow velocity. On digital subtraction angiography, the graft was considered patent, occluded, or patent but non-functional. Grafts were defined as non-functional when they had a diameter of less than 5F with the absence of opacification of the native coronary artery.

RESULTS

Of the 77 observations, 64 GEAs were patent angiographically, three were occluded and ten grafts were considered as patent but non-functional. Using color and duplex ultrasound, the GEA was identified in 65 out of 77 observations. There were no cases of false positive visualization of the GEA. All sonographically detected non-functional grafts (n = 7) had a cRI of greater than 0.60. When the non-visualized grafts are considered either non-functional or occluded, a cut-off value for a cRI of 0.60 results in a sensitivity and specificity of 100 and 75%, respectively.

CONCLUSION

We propose ultrasound as a primary screening tool for evaluating graft patency. While color Doppler is a suitable technique for graft visualization, spectral analysis with the calculation of a cRI is required for functional evaluation.

Vascular reactivity of arterial coronary artery bypass grafts--implications for their performance

Specific properties of the vessel wall of arteries employed as coronary bypass grafts are thought to play an important role in the short- and long-term performance of these conduits. Heterogeneity in the endothelial and smooth muscle cell function between different arteries may provide particular vessels with properties which will favor them for use as bypass conduits. The aim of this review is to provide an insight into how the vascular reactivity of presently used arterial conduits varies and to discuss the clinical implications of these findings both in terms of flow modulation in response to physiologic and exogenous vasoactive mediators and long-term patency.

Morphometric analysis of the right gastroepiploic artery and the internal mammary artery

BACKGROUND

The internal mammary artery (IMA) and the right gastroepiploic artery (RGEA) are frequently used as conduits for coronary artery bypass grafting.

METHODS

Morphometric measurements and histologic characteristics of the RGEA and the IMA were studied in 25 patients undergoing coronary artery bypass grafting.

RESULTS

External radius was found to be more in the IMA (range, 18 to 56 microns; mean, 39.56 microns) in comparison with the RGEA (range, 24 to 51 microns; mean, 32.52 microns; p < 0.01). There was no significant difference between the vessels in intimal thickness (IMA: 0.0 to 0.25 micron; mean, 0.05 micron; RGEA: 0.0 to 0.28 micron; mean, 0.09 micron), internal radius (IMA: 5 to 47 microns; mean, 28.40 microns; RGEA: 16 to 42 microns; mean, 23.56 microns), area of media (IMA: 1,690 to 3,476 microns2; mean, 2,777.52 microns2; RGEA: 1,659 to 3,600; mean, 3,012.44 microns2), intimal thickening index (IMA: 0.0 to 0.02; mean, 0.01; RGEA: 0.0 to 0.13; mean, 0.01), and medial index (IMA: 0.14 to 0.60; mean, 0.36; RGEA: 0.18 to 0.63; mean, 0.39). Histologic examination of the RGEA showed more defects in continuity of internal elastic lamina and rich smooth muscle cells in the media.

CONCLUSIONS

There was no difference in the morphometric measurements of the IMA and the RGEA except external radius, which was greater for the IMA. The histologic differences found in the RGEA may indicate an increased propensity for atherosclerosis of the RGEA as compared with the IMA. Some concern regarding the long-term patency of the RGEA in myocardial revascularization is warranted.

Which is the graft of choice for the right coronary and posterior descending arteries? Comparison of the right internal mammary artery and the right gastroepiploic artery

BACKGROUND

The graft of choice for the left anterior descending coronary artery is the left internal mammary artery because of superior long-term patency. However, controversy exists regarding the graft of choice for the right coronary artery and for the posterior descending branch.

METHODS AND RESULTS

Two types of pedicled arterial grafts were used for the right coronary and the posterior descending arteries in patients undergoing coronary bypass surgery between January 1991 and September 1994. Group A comprised 114 patients with a right internal mammary artery (RIMA) graft, and group B consisted of 127 patients with an in situ right gastroepiploic artery (R-GEA) graft. Mean age was 56.9 years in group A and 63.3 years in group B; 7.9% (9 of 114) and 33.9% (43 of 127) were diabetics in groups A and B, respectively. Overall mortality was 2.6% (3 deaths) for group A and 3.9% (5 deaths) for group B (P = NS). However, the prevalence of perioperative myocardial infarction in the right coronary artery distribution was significantly higher for group A (5.3%, or 6 of 114) than for group B (0.8%, or 1 of 127; P < .05), and the reoperation rate for graft failure (from 0 to 12 months after surgery) was significantly higher for the RIMA (4.4%, or 5 of 114) than for the R-GEA (0%; P < .05). Also, the prevalence of deep sternal wound infection in diabetics was significantly higher in group A (22.2%, or 2 of 9) than in group B (4.6%, or 2 of 43; P < .05).

CONCLUSIONS

Our preliminary results suggest that the failure rate of the RIMA graft is significantly higher, especially if used as a pedicled graft to the posterior descending artery. The risk of sternal wound complications is greater in diabetics if both internal mammary arteries are used for grafting. Therefore, the R-GEA graft is preferred in diabetics and whenever the posterior descending artery is the target vessel.

Late endothelial function of free and pedicled internal mammary artery grafts

The internal mammary artery has greater long-term patency than the saphenous vein when used for coronary bypass grafting. Therefore, bilateral use of the internal mammary artery for grafting with the right internal mammary artery used as a "free" graft may result in improved graft survival. The study objectives were to compare the endothelial-dependent and -independent vasodilatory response in free and pedicled internal mammary artery grafts in patients who had previously undergone coronary surgery. Free (group 1, n = 8) and pedicled (group 2, n = 7) internal mammary artery grafts were studied by comparing the response to selective infusion of the endothelial-dependent vasodilator substance P (1.4 up to 22.4 pmol/min in doubling dose increments) followed by isosorbide dinitrate (2 mg over 2 minutes), in patients undergoing coronary angiography, 1 month to 6 years after coronary surgery. Maximal dilatory response to substance P was 8.7% +/- 1.8% in pedicled grafts compared with 8.8% +/- 2.3% in free grafts (p = not significant), with the dose response for both groups being similar. Infusion of isosorbide dinitrate produced only minimal further dilatation in both groups. No significant difference was found in endothelium-dependent and -independent vasodilatory response between free and pedicled internal mammary artery grafts, suggesting that the use of the free right internal mammary artery and other arterial grafts may enhance graft survival.

Vasoconstrictor profile of the inferior epigastric artery

The inferior epigastric artery is a putative arterial bypass graft. The receptor mechanisms that control vascular tone are thought to play a role in the performance of bypass conduits. We have compared the vascular reactivity of the inferior epigastric artery with that of the internal mammary artery. Segments from a total of 15 inferior epigastric and 12 internal mammary arteries were examined for their response to increasing concentrations of noradrenaline, 5-hydroxytryptamine, dopamine, histamine, endothelin-1, or the thromboxane analogue U46619. The responsiveness of the smooth muscle was significantly greater in the inferior epigastric artery (p < 0.05) as judged by contractions elicited by 90 mmol/L potassium chloride. However, although the response of the inferior epigastric artery tended to be greater, this significant enhancement of smooth muscle function was not paralleled by the maximal responses of noradrenaline, 5-hydroxytryptamine, dopamine, histamine, or endothelin-1. However, the tension generated in response to U46619 did differ significantly, with maximal responses in the inferior epigastric and internal mammary arteries of 59.2 +/- 8.3 mN and 35.0 +/- 3.6 mN, respectively. When receptor function was compared by expressing the response as a percentage of that of 90 mmol/L potassium chloride, it was revealed that noradrenaline was capable of inducing significantly greater relative contractions in the internal mammary artery (114.8% +/- 20.5%) as compared with the inferior epigastric artery (49.9% +/- 19.1%); the potency of this constrictor was sixfold greater in the internal mammary artery.(ABSTRACT TRUNCATED AT 250 WORDS)

Different vascular reactivity of human internal mammary and inferior epigastric arteries in vitro

Vascular responses to endogenous agonists may determine patency rates of bypass graft conduits. The effect of constrictors (noradrenaline, phenylephrine, serotonin, histamine, angiotensin II) and dilators (acetylcholine, substance P, bradykinin, nitroglycerin) were compared in human internal mammary and inferior epigastric arteries in vitro. The latter vessel type has been recently advocated as an additional conduit for coronary artery bypass grafting. Whereas the alpha-adrenoceptor- (noradrenaline, phenylephrine) and serotonin receptor-mediated contractions were similar in both vessels, histamine-induced contractions were greatly enhanced in internal mammary arteries (maximal responses in percent of 80 mmol/L KCl, 131% +/- 15% versus 59% +/- 8%). Maximal contractions in response to angiotensin II were greater in inferior epigastric arteries (50% +/- 6% versus 25% +/- 5%). The endothelium-independent relaxations in response to nitroglycerin were identical in both vessels. In contrast, the endothelium-dependent relaxations in response to acetylcholine, substance P, and bradykinin were significantly greater in the inferior epigastric than in the internal mammary arteries (maximal relaxations expressed as percent of prostaglandin F2 alpha-induced precontraction: acetylcholine, 94% +/- 5% versus 77% +/- 5%; substance P, 85% +/- 4% versus 24% +/- 5%; bradykinin, 77% +/- 5% versus 26% +/- 3%). It is concluded that the inferior epigastric artery has a high endothelial capacity to release endothelium-derived relaxing factor. It appears that the inferior epigastric artery possesses credentials to be successfully used for coronary artery bypass grafting.

Clinical experience with the right gastroepiploic artery in coronary artery bypass grafting

The excellent long-term results with the internal mammary artery for coronary artery bypass grafting have prompted the search for other conduits with similar characteristics. From December 1989 to December 1991, the right gastroepiploic artery (RGEA) has been used as an in situ graft to the posterior descending coronary artery in 51 patients at the Montreal Heart Institute. The patients' age averaged 50 +/- 11 years. Three-vessel coronary artery disease was present in 41 patients and two-vessel disease in the remaining 10 patients. In all but 1 patient, bilateral internal mammary artery grafting was performed in addition to RGEA grafting. The number of grafts per patient averaged 3.2 +/- 0.8. There was no operative mortality. Morbidity was minimal with only myocardial infarction and a pleural effusion in 1 patient. In 1 patient, a splenectomy had to be performed because of iatrogenic tear during dissection of the RGEA. The average hospital stay was 8.2 +/- 2.6 days. Enteral nutrition was resumed on average 2 days after operation. Angiographic evaluation of RGEA grafts was performed before discharge or within the first month after surgery in 31 patients. In 28 patients (28/31, 90%) the RGEA graft was patent, two grafts were occluded, and in the remaining patient, the graft could not be visualized due to technical difficulties during angiography. A second angiographic evaluation was performed in 5 patients, 1 year after operation. Four RGEAs were patent and 1 was occluded. Clinical follow-up averaged 4 months (range 1 to 15 months).(ABSTRACT TRUNCATED AT 250 WORDS)

Action of vasoactive intestinal peptide and distribution of its binding sites in vessels used for coronary artery bypass grafts

In an attempt to establish the possible role of vasoactive intestinal peptide (VIP) in the regulation of vasomotor tone of coronary artery bypass grafts, this study examined the action of this peptide and the distribution of [125I]VIP binding sites in isolated human gastroepiploic artery (GEA), internal mammary artery (IMA) and saphenous vein. VIP (10(-10)-3 x 10(-7) M) elicited concentration-dependent relaxations in ring segments that were preconstricted with the thromboxane analog U46619. The maximal response was mean +/- SEM 79 +/- 4%, 52 +/- 8% and 23 +/- 3% of glyceryl trinitrate (3 x 10(-5) M)-induced maximal smooth muscle relaxation in the GEA, IMA and saphenous vein, respectively. Both receptor-binding and competition studies indicated that there was a higher density of [125I]VIP binding to smooth muscle cells of the GEA and IMA than to the saphenous vein. Total binding, at 50pM [125I]VIP, was 604 +/- 89, 381 +/- 64 and 87 +/- 12 amol/mg wet weight in the GEA, IMA and saphenous vein, respectively. Dense binding of [125I]VIP was associated with the tunica media in all the vessels studied. There was also binding to perivascular regions with no obvious binding to endothelial cells. These data demonstrate that arterial grafts, particularly the GEA, are more sensitive to the relaxant effect of VIP and this may possibly be due to a higher receptor density.

Characterization of 5-HT receptors in simian isolated gastroepiploic artery

The vascular responses of simian gastroepiploic arteries to 5-hydroxytryptamine (5-HT), 5-carboxamidotryptamine (5-CT, a selective 5-HT1-like receptor agonist), 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT, a selective 5-HT1A receptor agonist), m-trifluoromethylphenylpiperazine (TFMPP, a selective 5-HT1B receptor agonist), noradrenaline and KCl were examined in isolated, cannulated and perfused preparations. 5-HT induced dose-dependent vasoconstrictions more potently than noradrenaline did. The rank order of potency was 5-HT > noradrenaline > 5-CT >> 8-OH-DPAT = TFMPP. 5-HT- and 5-CT-induced vasoconstrictions were not significantly changed by endothelial denudation, although acetylcholine-induced vasodilatations were abolished. 5-HT-induced vasoconstrictions were depressed by phentolamine (an alpha-adrenoceptor antagonist), diltiazem (a calcium ion channel inhibitor), methysergide (a 5HT1- and 5HT2-receptor antagonist) and ketanserin (a selective 5-HT2 receptor antagonist). Noradrenaline-induced vasoconstrictions were readily inhibited by phentolamine and ketanserin. 5-CT-, 8-OH-DPAT- and TFMPP-induced vasoconstrictions were inhibited by both methysergide and ketanserin. KCl-induced vasoconstrictions were blocked by diltiazem. From these results, we conclude that (1) the simian gastroepiploic artery contains 5-HT receptors, (2) 5-HT1-like and 5-HT2 receptors are involved in the vasoconstriction of the simian gastroepiploic artery, and (3) the vasoconstriction is at least partially related to the activation of calcium ion channels.