Effects of auriculopalpebral nerve block on ocular parameters in dogs

The objective of this study was to compare the effects of two local anesthetics used on auriculopalpebral block on eyelid akinesia, tear production, intraocular pressure (IOP) and tear break-up time (TBUT) in conscious dogs. A blind, randomized, prospective study was conducted to determine the effects of auriculopalpebral block using ropivacaine 0.75% and bupivacaine 0.5% in 12 healthy non-brachycephalic dogs (24 eyes). Threat response and eyelid reflex tests, Schirmer tear test (STT), IOP and tear break-up time were conducted before blockage and at 30, 60, 120, 240 and 360 minutes after application. A difference was observed between the values found at 30, 60, 120 and 240 minutes compared to baseline for threat response and eyelid reflex tests in the two groups evaluated, proving eyelid akinesia after blockages. No difference was found for STT, IOP and TBUT between baseline values and post-anesthesia times or between groups. It was possible to conclude that ropivacaine and bupivacaine on auriculopalpebral block in conscious dogs promoted eyelid akinesia for at least 240 minutes, not altering ocular physiological parameters of tear production, intraocular pressure, and tear break-up time after blockages.

Thyroid hormone activated upper gastrointestinal motility without mediating gastrointestinal hormones in conscious dogs

This study was conducted to clarify the relationship between thyroid function and gastrointestinal motility. We established an experimental configuration in which the feedback of thyroid function was completely removed using conscious dogs. With hypothyroidism, time of phase I of interdigestive migrating contractions (IMC) was longer, time of phase II and phase III was significantly shortened, and both the continuous time of strong tetanic contraction at antrum and 10-h frequency of phase III counted from the first IMC after meal significantly decreased. Whereas, hyperthyroidism caused the opposite events to those with hypothyroidism. Furthermore, We found giant migrating contractions (GMC) occurred from the upper gastrointestinal tract when we administrated high dose of thyroid hormone. One GMC occurred from anal sides propagated to cardiac, and this propagation was similar to the emesis-like interdigestive motor activity, the other GMC occurred from oral sides propagated to anal sides and this was similar to the diarrhea-like interdigestive motor activity. We examined the relationship between thyroid function and gastrointestinal hormones including of ghrelin, GLP-1, and cholecystokinin (CCK). However, we could not find significant differences under different thyroid hormone status. This is the first report that thyroid hormone activated upper gastrointestinal motility without mediating gastrointestinal hormones.

Evaluation of changes in gastrointestinal motility caused by altered thyroid function in conscious dogs

This study was conducted to clarify the relationship between thyroid function and gastrointestinal motility. We established an experimental configuration in which the feedback of thyroid function was completely removed using conscious dogs. With hypothyroidism, time of phase Ⅰ of interdigestive migrating contractions (IMC) was longer, time of phase Ⅱ and phase Ⅲ was significantly shortened, and both the continuous time of strong tetanic contraction at antrum and 10-hours frequency of phase Ⅲ counted from the first IMC after meal significantly decreased. Whereas, hyperthyroidism caused the opposite events to those with hypothyroidism. Furthermore, We found giant migrating contractions (GMC) occurred from the upper gastrointestinal tract when we administrated high dose of thyroid hormone. One GMC occurred from anal sides propagated to cardiac, and this propagation was similar to the emesis-like interdigestive motor activity, the other GMC occurred from oral sides propagated to anal sides and this was similar to the diarrhea-like interdigestive motor activity. We examined the relationship between thyroid function and gastrointestinal hormones including of ghrelin, GLP-1, and cholecystokinin (CCK). However, we could not find significant differences under different thyroid hormone status. This is the first report that thyroid hormone activated upper gastrointestinal motility without mediating gastrointestinal hormones.

Abstract 13050: Acute Alcohol-Induced Enhanced Cardiac Depression in a Canine Model of Chronic Alcohol Consumption: Adverse Effects on Left Ventricle and Myocyte Contraction, [Ca 2+ ] i Transient and Ca 2+ Current

Background: Acute alcohol ingestion produces transient RAS activation. Alcoholics have an enhanced RAS activation after acute ethanol ingestion. Thus, chronic alcohol users may have enhanced cardiac functional responses to acute alcohol intake. However, it is unclear whether and how chronic alcohol intake alters cardiac response to acute alcohol exposure. We tested the hypothesis that acute alcohol may exacerbate cardiac depression and [Ca 2- ] i dysregulation, thus play important role in development of irreversible cardiomyopathy in alcoholics. Methods: We compared LV and cardiomyocyte response to acute alcohol in 6 chronically-instrumented conscious dogs before and 6 months after the once daily ingestion of alcohol (400 ml, 22% providing 33% of total daily caloric intake). Results: In conscious dogs, 6 months of alcohol significantly decreased LV contractility by 48% measured by the slopes of pressure-volume relations (E ES , 48%, 4.4 vs 8.4 mmHg/ml and M SW , 50.8 vs 98.6 mmHg) and increased the time constant of relaxation (τ, 78%, 47.8 vs 26.9 ms). In the alcoholic animals, when compared with the same animals prior to alcohol, acute alcohol (0.2 g/kg, iv, plasma level 62.3 ± 8 mg/dL) caused a greater decrease in LV contractility (47% vs 23%) and increase in τ (27% vs11%). In isolated myocytes, abrupt exposure to alcohol (250 mM) produced significant decreases in cell contraction, [Ca 2+ ] i transient ([Ca 2+ ] i ) and Ca 2+ current (I Ca,L ) in both normal and alcoholic myocytes. However, compared with the isolated cells obtained from LV biopsied tissues of the same animals prior to alcohol, the acute alcohol-induced decrease in I Ca,L (alcoholic: 50%, 1.3 vs 2.6; normal: 29%, 4.0 vs 5.6 pA/pF) was much greater in the alcoholic myocytes, the resulting reductions in the cell contractility, dL/dtmax (alcoholic: 46%, 36vs67; normal: 24%, 82vs108 μm/s), the percent shortening (49% vs 24%) and relengthening, dR/dtmax were doubled. Conclusion: In chronically alcohol-fed dogs, acute alcohol produces increased direct inhibition in LV and myocyte contractility, relaxation and exacerbates [Ca 2+ ] i hemostasis. The chronic alcohol-induced increased cardiac sensitivity to acute alcohol may play an important role in the functional impairment in alcoholic cardiomyopathy.

Abstract 13027: Differential Direct Effects of Equal Hypotensive Natriuretic Peptides (NPs) of ANP, BNP and CNP on Left Ventricular Contractile Performance in Heart Failure: Assessment by Left Ventricular Pressure-Volume Analysis

Background: Natriuretic peptides (NPs) play a crucial role in maintaining cardiovascular homeostasis. NPs stimulate the production and release of cGMP, leading to the vasodilating and natriuretic actions. In heart failure (HF), circulating and cardiac ANP, BNP, and CNP are increased and exhibit a range of actions. However, although they serve as therapeutic agents, their direct cardiac effects in HF are uncertain due to the confounding influence of NPs-produced changes in loading condition on conventional measures of LV function. We test the hypothesis that equal hypotensive 3 NPs may have different inotropic effects on LV contractility and relaxation in HF. Methods: We assessed the cardiac effects of intravenous infusion (20 min) of ANP (2 μg/kg plus 0.5 μg/kg/min), BNP (2 μg/kg plus 0.04 μg/kg/min) and CNP (2 μg/kg plus 0.4 μg/kg/min) on different days in 6 instrumented conscious dogs with pacing-induced HF by using pressure (P)-volume (V) analysis, a load-independent measure of LV contractility. Results: Versus baselines, 3 NPs produced arterial vasodilation with similar and significant decreases in LV end-systolic pressure (10 to 12 mmHg) with relatively unchanged heart rate. ANP caused significant reductions (13%) of E ES (4.2 vs 4.8 mmHg/ml) and M SW (54.6 vs 62.8 mmHg). The time constant of LV relaxation (τ, 45.1 vs 37.6 ms) was lengthened. The LV-arterial coupling, E ES / E A (arterial elastance) (0.57 vs 0.58) was unaltered. The peak mitral flow, dV/dt max was only increased by 7% (178 vs 166 ml/s). With BNP, there were no significant changes in E ES (5.1 vs 4.9 mmHg/ml) and M SW, but E ES /E A was improved 30% (0.74 vs 0.57) due to decreased E A . τ (33.4 vs 37.9 ms) was significantly shortened and dV/dt max increased 15% (189 vs 165 ml/s). In contrast, CNP produced significant increases (~30%) in E ES (6.3 vs 4.8 mmHg/ml) and M SW (80.5 vs 62.4 mmHg) with enhanced increase in E ES /E A (50%, 0.87vs 0.58), but decrease in τ (25%, 28.4 vs 38.1 ms) and significantly greater augmented dV/dt max (25%, 205 vs 164 ml/s). Similar observations of NPs were made at constant heart rate, or after autonomic blockade. Conclusion: In conscious dogs with HF, equal hypotensive ANP, BNP and CNP have negative, no effect, and positive inotropic effects on LV contractility and relaxation, respectively.