Cholecystokinin as a regulator of cardiac function and postprandial gastrointestinal blood flow in rainbow trout (Oncorhynchus mykiss)

Abstract

We have studied the potential role of CCK as a regulator/modulator of the postprandial increase in gastrointestinal blood flow. Rainbow trout (Oncorhynchus mykiss) were instrumented with pulsed Doppler flow probes to measure the effects of CCK on cardiac output and gastrointestinal blood flow. Furthermore, vascular preparations were used to study the direct effects of CCK on the vessels. In addition, we used in situ perfused hearts to further study the effects of CCK on the cardiovascular system. When the sulfated form of CCK-8 was injected at a physiological concentration (0.19 pmol/kg) in vivo, there was a significant increase in the gastrointestinal blood flow (18 +/- 4%). This increase in gastrointestinal blood flow was followed by a subsequent increase in cardiac output (30 +/- 6%). When the dose was increased to 0.76 pmol/kg, there was only a 14 +/- 6% increase in gastrointestinal blood flow; possibly due to a dose-dependent increase in the gill vascular resistance as previously reported or a direct effect on the heart. Nevertheless, CCK did not affect the isolated vessel preparations, and thus, it seems unlikely that CCK has a direct effect on the blood vessels of the second or third order. CCK did, however, have profound effects on the dynamics of the heart, and without a change in cardiac output, there was a significant increase in the amplitude (59 +/- 4%) and rate (dQ/dt: 55 +/- 4%; -dQ/dt: 208 +/- 49%) of the phasic flow profile. If and how this might be coupled to a postprandial gastrointestinal hyperemia remains to be determined. We conclude that CCK has the potential as a regulator of the postprandial gastrointestinal blood flow in fish and most likely has its effect by inducing a gastrointestinal hyperemia. The mechanism by which CCK acts is at present unknown.

Post-Surgical Analgesia in Rainbow Trout: Is Reduced Cardioventilatory Activity a Sign of Improved Animal Welfare or the Adverse Effects of an Opioid Drug?

“…Indeed, when reviewing the current literature on cardioventilatory data for similar sized rainbow trout at ∼10°C it is obvious that our values are considerably lower than most previous values. For example, the mean heart rate of the untreated control group on day 5 in the present study (30.2±2.4 beat min −1 ) is 13–26 beats min −1 lower than most values reported in the literature using appropriate techniques and a post-surgical recovery time of at least 24 h [15], [21], [33]–[35]. The already remarkably low heart and ventilation rates were further reduced after an administration of buprenorphine, resulting in values 21.9±2.6 beat min −1 and 40.0±1.7 breaths min −1 , respectively, which to our knowledge, are the lowest values ever reported for rainbow trout at 10°C.…”

“…This procedure was chosen to mimic a surgical technique that can be considered rather invasive and that is routinely used in rainbow trout, e.g. to access the coeliacomesenteric artery and other organs in the abdominal cavity [19]–[21]. The surgery took around 15 min, and including anaesthesia and post-operative wake up the entire procedure took around 30 min.…”

Sympathetic, parasympathetic and enteric regulation of the gastrointestinal vasculature in rainbow trout (Oncorhynchus mykiss) under normal and postprandial conditions

“…It could also indicate that there is a change in the tonus of the smooth musculature of the gastrointestinal tract leading to a change in the transmural pressure of the vasculature. This is also unlikely considering that there is a considerable vasorelaxation in isolated gastrointestinal vessels when adding atropine (Seth et al, 2010). The most likely explanation is that the effect instead represents a pharmacological artifact.…”

“…The correct dosage was obtained using in-situ perfused hearts (N4) as previously described by Seth et al (Seth et al, 2010) and the concentration of TTX in the perfusate was increased in a stepwise manor until a change in the contractility of the heart was noticed. Additional in vivo trials on anaesthetized fish (N4) were also conducted.…”

The Gastrointestinal Circulation: Physiology and Pathophysiology

“…The potential for these peptides to mediate the postprandial hyperemia is based on the fact that they typically produce vasodilation in the intestine. However, with few exceptions [e.g., CCK in rainbow trout (435) and neurotensin in the python (459)], the concentration of the peptide that must be infused in the intestinal arterial supply to elicit vasodilation far exceeds the levels achieved in intestinal venous blood postprandially (143,146,435). While this is also the case for VIP (143), studies have demonstrated that administration of a VIP blocking antibody reduces the jejunal blood flow response to micellar oleic acid by approximately 70% (412) (Fig.…”