The Effect of Increasing Bath Temperature on the Contractile Responses of the Large Gut in Adult and Neonate Rats.

Introduction Earlier reports on the effect of temperature on gut motility concentrated on experiments conducted on the small intestines of adult animals. The effect of temperature on the large intestine, particularly in neonates, warrants further investigation. The current study investigated the effect of a temperature increase and its mechanism in the colon and rectum of neonate and adult rats. Methods and materials In an organ bath preparation, segments from the colon and rectum were subjected to increasing bath temperatures (37°C-40°C). In other groups, pretreatment with capsazepine (1 µM) and Nω-nitro-l-arginine methyl ester (L-NAME) (100 µM) was done, in different groups, to assess their impact on temperature-induced contractile response. Results Increasing the bath temperature significantly reduced the contractile tension in the colon and rectum. When L-NAME (100 µM)-pretreated segments of the colon and rectum were subjected to different bath temperatures, the contractile tension increased compared to the contractile tension at different bath temperatures without any drug. Capsazepine (1 µM) pretreatment, on the other hand, enhanced the decrease in the contractile tension in the colon and rectum of adult rats compared to the contractile tension produced at different bath temperatures without any drug, while in neonates, capsazepine (1 µM) pretreatment caused a rise in the contractile tension in the rectum with no effect in the colon. Increased bath temperature from 37°C to 40°C increased the contractile frequency in the colon and rectum in both adult and neonate rats. Pretreatment with L-NAME (100 µM) and capsazepine (1 µM) in adults and L-NAME (100 µM) in neonates caused an increase in the contractile frequency in both the colon and rectum; on the other hand, capsazepine pretreatment did not affect the contractile frequency in the colon and rectum of neonate rats compared to the contractile frequency produced at different bath temperatures without any drug. Conclusion The contractile response of rats' large intestines, colon, and rectum to increasing temperatures may involve nitric oxide (NO)-mediated and transient receptor potential vanilloid-1 (TRPV1)-mediated mechanisms. The effects of capsazepine on the colon and rectum of adults and neonates differ, possibly due to the TRPV1-mediated mechanism not developing properly in the neonate and developing later in adulthood.

A Comparative Study of Effects of 28-Day Exposure of Bisphenol A and Bisphenol S on Body Weight Changes, Organ Histology, and Relative Organ Weight.

CONTEXT: Bisphenol A (BPA), a known endocrine disrupting chemical, is of widespread use in manufacturing of plastic products. Documenting ill health effects of BPA has led the plastic industrialists to replace BPA by its alleged safer alternative, bisphenol S (BPS). BPS belongs to the same chemical family and shares endocrine disrupting properties with BPA. AIMS: We compared the effects of 28-day exposure of BPA and BPS on body weight changes, organ histology, and relative organ weight in rats. In addition, we detected BPA and BPS in the rat's blood serum. SETTINGS AND DESIGN: Adult male albino rats were administered BPA (50 mg/kg/day) or BPS (50 mg/kg/day) or equivolume vehicle in different groups by oral gavage for 28 days. SUBJECTS AND METHODS: The weight of each rat was noted at the commencement of the study and weekly afterward. On 29th day, the animals were sampled for whole blood and then sacrificed. The dissected out wet viscera were weighed and subjected to the standard protocol for histological examination. Serum samples were prepared and analyzed for the detection of BPA and BPS by high-pressure liquid chromatography. STATISTICAL ANALYSIS USED: Paired and unpaired Student's t-test, one-way ANOVA test, and Bonferroni test for multiple comparisons were used, as required for statistical analysis, and P < 0.05 was considered statistically significant. RESULTS: Both BPA and BPS produced similar detrimental changes in body weight, histology of stomach, small intestine, lung, and kidney, and relative organ weight of lung and kidney. BPA and BPS detected in the serum of rats were nearly 45 times of the control. CONCLUSIONS: Present data suggest caution about the application of BPS as a substitute of BPA.

Intra-arterial Instillation of a Nociceptive Agent Modulates Cardiorespiratory Parameters Involving 5-HT3 and TRPV1 Receptors in Anesthetized Rats.

BACKGROUND: Since long back, it has been a matter of discussion regarding the role of peripheral blood vessels in the regulation of cardiorespiratory (CVR) system. OBJECTIVE: The role of 5-HT3 and TRPV1 receptors present on perivascular nerves in elicitation of CVR reflexes was examined after intra-arterial instillation of bradykinin in urethane anesthetized rats. MATERIALS AND METHODS: Femoral artery was cannulated retrogradely and was utilized for the instillation of saline/agonist/antagonist and recording of blood pressure (BP), using a double ported 24G cannula. BP, respiration and ECG were recorded for 30 min after bradykinin (1 µM) in the absence or presence of antagonists. RESULTS: Instillation of bradykinin produced immediate hypotensive (40%), bradycardiac (17%), tachypnoeic (45%) and hyperventilatory (96%) responses of shorter latencies (5-8 s) favoring the neural mechanisms in producing the responses. In lignocaine (2%) pretreated animals, bradykinin- induced hypotensive (10%), bradycardiac (1.7%), tachypnoeic (13%) and hyperventilatory (13%) responses attenuated significantly. Pretreatment with ondansetron (100 µg/kg), 5-HT3-antagonist attenuated the hypotensive (10%), bradycardiac (1.7%), tachypnoeic (11%) and hyperventilatory (11%) responses significantly. Pretreatment with capsazepine (1 mg/kg), transient receptor potential vanilloid 1- antagonist blocked the hypotensive (5%), bradycardiac (1.2%), tachypnoeic (6%) and hyperventilatory (6%) responses significantly. CONCLUSION: In conclusion, presence of a nociceptive agent in the local segment of an artery evokes vasosensory reflex responses modulating CVR parameters involving TRPV1 and 5-HT3 receptors present on the perivascular sensory nerve terminals in anesthetized rats.

A functional study on small intestinal smooth muscles in jejunal atresia.

AIM: The present study was aimed to assess the contractile status of neonatal small intestinal smooth muscle of dilated pre-atretic part of intestinal atresia to resolve debatable issues related to mechanisms of persistent dysmotility after surgical repair. MATERIALS AND METHODS: A total of 34 longitudinally sectioned strips were prepared from pre-atretic dilated part of freshly excised 8 jejunal atresia type III a cases. Spontaneous as well as acetylcholine- and histamine-induced contractions were recorded in vitro by using organ bath preparations. Chemically evoked contractions were further evaluated after application of atropine (muscarinic blocker), pheniramine (H1 blocker), and lignocaine (neuronal blocker) to ascertain receptors and neuronal involvement. Histological examinations of strips were made by using Masson trichrome stain to assess the fibrotic changes. RESULTS: All 34 strips, except four showed spontaneous contractions with mean frequency and amplitude of 5.49 ± 0.26/min and 24.41 ± 5.26 g/g wet tissue respectively. The response to ACh was nearly twice as compared to histamine for equimolar concentrations (100 µM). ACh (100 µM) induced contractions were attenuated (by 60%) by atropine. Histamine (100 µM)-induced contractions was blocked by pheniramine (0.32 µM) and lignocaine (4 µM) by 74% and 78%, respectively. Histopathological examination showed varying degree of fibrotic changes in muscle layers. CONCLUSIONS: Pre-atretic dilated part of jejunal atresia retains functional activity but with definitive histopathologic abnormalities. It is suggested that excision of a length of pre-atretic part and early stimulation of peristalsis by locally acting cholinomimetic or H1 agonist may help in reducing postoperative motility problems in atresia patients.

In Vitro Evaluation of Carbachol and Endothelin on Contractility of Colonic Smooth Muscle in Hirschsprung's Disease.

Background: The hypomotility of colon observed in Hirschsprung's disease (HD) has been attributed to congenital aganglionosis only. So far, it is not clear whether the contractility of colonic smooth muscle in this condition is altered or not. Therefore, the present study attempted to understand the contractile status of colonic segments of HD patients by examining carbachol and endothelin (ET-1) evoked colonic smooth muscle contractions in vitro . Methods: Contractile responses were recorded from strips of colonic segments obtained from HD patients, using organ bath preparations. Cholinergic agonist carbachol and ET-1 along with their antagonists were used to evoke contractile responses. Thereafter, the samples were histopathologically confirmed for HD. Results: Colonic strips of HD did not show any spontaneous contractions but responded to carbachol and ET-1 to a lesser extent. In HD, response of carbachol was blocked by atropine and hexamethonium by nearly 73% and 50% respectively. ET-1 induced contractile responses were blocked by ET-A and ET-B antagonist up to 40%, signifying the possible role of ET-A and ET-B receptors in HD colon contractility. Conclusion: As evidenced by lack of spontaneous contractions and impaired carbachol and ET-1-induced contractile responses, it is concluded that, in addition to aganglionosis, decreased contractility of colonic smooth muscle may contribute to hypomotility observed in patients with HD.

In vitro study of acetylcholine and histamine induced contractions in colon and rectum of adult and neonate rats.

Contractile mechanisms of different parts of the gut in adult and neonate may not be identical due to developmental processes. The present study was undertaken to investigate acetylcholine (ACh) and histamine induced contractile responses of colon and rectum in adult and neonatal albino rats. Contractile responses were recorded from isolated in vitro preparations. The dose-response curve for ACh (0.001-100 microM) revealed dose dependent increase in contractile responses. A significantly (P < 0.05) greater contractile responses (g/g wet tissue) was observed in rectum as compared to colon. Atropine pretreatment significantly blocked ACh responses in both rectum and colon. The blockade was higher in adult preparations. The dose-response study for histamine (0.001-100 microM) did not show any significant difference between rectum and colon. Histamine (100 microM) induced contractions were significantly (P < 0.05) increased after pretreatment with pheniramine (100 microM) in adult rectum. This potentiating response of pheniramine was absent in neonate rectum. Such effect was also not seen in colon of both adult and neonate. The present investigation indicates that the contractile responses induced by ACh are similar in both adult and neonate, excepting that the blocking effect of atropine in colon was more pronounced in adult as compared to neonate. Further, the results also indicated different mechanism of histamine action in adults and neonates as evidenced by the significant enhancement of contractions by pheniramine only in adult rectum. Therefore, the present results indicate the existence of a different cholinergic and histaminergic activity in adult and neonate as well as in rectal and colonic tissue.

Pouch colon associated with anorectal malformations fails to show spontaneous contractions but responds to acetylcholine and histamine in vitro.

PURPOSE: Congenital pouch colon (CPC) associated with anorectal malformation (ARM) is most commonly reported from Northern India. So far, no physiologic study comparing the detailed contractile status of CPC with non-CPC conditions are available. The present article deals with the contractile study and histopathologic observations in CPC, which may be useful for better surgical management. METHODS: Freshly excised 12 neonatal CPC and similar number of non-CPC (control) specimens were transferred to ice-cold (4 degrees C-6 degrees C) Krebs-Ringer solution bubbled with 100% oxygen. Longitudinally prepared 2 to 4 colonic strips were obtained from central part of each specimen and subjected to the contraction recording after exposure to cumulative concentrations of acetylcholine (ACh) and histamine. Acetylcholine-induced contractions were evaluated after application of atropine (muscarinic blocker), and histaminergic contractions were recorded after pheniramine (H(1) blocker), lignocaine (neuronal blocker), and atropine. Histopathologic observations were made by using H&E and Masson trichrome stains. RESULTS: Control specimens showed spontaneous contractions, but CPC strips did not. Both control and CPC responded to ACh and histamine. The response to histamine was greater (P < .05) in CPC as compared to control, whereas the response to ACh was more (P < .05) in control. In CPC, response of histamine (100 micromol/L) was blocked by pheniramine (0.32 mmol/L) and lignocaine (4 mmol/L) by 97% and 80%, respectively, and enhanced by 57% after preapplication of atropine (10 micromol/L). Acetylcholine (100 micromol/L)-induced contractions were attenuated (86%) in presence of atropine. Histopathologic examination showed fewer mature ganglion cells with various changes in muscle layers including fibrosis, disruption, hypertrophy, atrophy, and constriction bands. CONCLUSION: Congenital pouch colon associated with ARM lacks normal spontaneous contractions but retains ACh and histamine-induced contractility. In view of the functional and histologic abnormalities, we propose that CPC associated with ARM is an abnormally functional and developed tissue. Therefore, resection of the pouch should be considered for better functional outcome of the remaining bowel.

In vivo and in vitro bradycardia induced by local anesthetics is potentiated by calcium channel blockers.

The present study examined the interactions of local anesthetics (LA) and calcium channel blockers (CCBs) on rhythmicity of heart using in vivo and in vitro experiments. ECG recordings were made from the anesthetized rats for in vivo preparations and spontaneously beating isolated rat right atrial potential for the in vitro experiments. The in vivo experiments with LA showed dose-dependent bradycardia with lignocaine (LIG, 100-500 microg/kg) and bupivacaine (BUP, 10-100 microg/kg). BUP was 4-5 times more potent than LIG. Verapamil (VML) and diltiazem (DTZ), CCBs also produced dose (10-100 microg/kg) -dependent bradycardia. However, none of them affected the PR/QT interval or QRS complex. Further, LA-induced bradycardia was potentiated by CCBs. In addition, flattening of P-wave in ECG was observed with doses (10-25 microg/kg) of LA in the presence of CCBs. Similarly, the in vitro experiments demonstrated a concentration-dependent decrease in atrial rate by BUP or VML. The BUP-induced decrease was potentiated in the presence of VML. Thus, the results suggest that CCBs potentiate the LA-induced bradycardia by involving pacemaker activity. Further, the flattening of P-wave in ECG serves as an early indicator of the cardiotoxicity produced by these drugs.

Cardiac dysrhythmia produced by Mesobuthus tamulus venom involves NO-dependent G-Cyclase signaling pathway.

Role of G-protein coupled pathways in modulating the cardiotoxic effects produced by Indian red scorpion (Mesobuthus tamulus) venom were examined. The isometric contractions of spontaneously beating or paced (3.5 Hz) rat right atrial preparations in vitro were recorded. The cumulative concentration (0.01-3.0 microg/ml)-response of venom on spontaneously beating atria exhibited a marked decrease in rate (by 55%) and an increase in force (by 92%) only at a higher concentration (3.0 microg/ml). The venom-induced decrease in rate and increase in force were sensitive to atropine, N-omega-nitro-L-arginine methylester (NO synthase inhibitor) and methylene blue (guanylyl cyclase inhibitor). Further, nifedipine, a Ca(2+) channel antagonist, blocked the force changes but not the rate changes induced by venom. In the paced atrium, on the other hand, a concentration-dependent decrease in force was observed, and at 3 microg/ml, the decrease was 50%. Pretreatment with nifedipine, but not with methylene blue, significantly attenuated the venom-induced force changes in paced atrium. The observations of this study demonstrate that the venom-induced atrial dysrhythmia is mediated through the muscarinic receptor-dependent NO-G-cyclase cell-signaling pathways.

Ptychodiscus brevis toxin decreases the spontaneous activity of rat right atria involving muscarinic receptors and potassium channels.

Marine dinoflagellate Ptychodiscus brevis toxin (PbTx), is known to produce toxic effects on cardiovascular system. The present experiments were conducted to evaluate the effect of synthetic phosphorus containing Ptychodiscus brevis toxin on spontaneously beating right atrium in vitro. The PbTx (0.84-84 microM) decreased the rate and force of right atrial contractions in a concentration-dependent manner. Ethanol, a vehicle present in highest concentration of PbTx, had no effect on atrial rate or force of contraction. Pretreatment with atropine blocked the PbTx-induced decrease in atrial rate and force of contraction. The tetraethylammonium, a potassium channel blocker, blocked the PbTx-induced decrease in atrial rate and force, where as, L-type of calcium channel blocker, nifedipine blocked the PbTx-induced force of contraction but not the rate changes. The results indicate that the PbTx decreased the atrial rate and force of contraction via cholinergic receptors involving K+ channel.

Sleep duration of an individual has adverse influence on auditory episodic memory.

The present study evaluated the influence of habitual sleep duration on episodic memory in a wakeful state. Episodic memory was assessed for auditory and visual processing pathways. A total of 96 medical students (53 male and 43 female, between the age group 18-23 years) accustomed to different sleep durations volunteered in the tests. The tests included auditory free recall of 10 common words, pictorial free recall of 10 pictures and recognition of 10 miniature animal replicas with 10 distracters. There was no gender-related difference in the visual and the auditory memory scores. The visual episodic memory scores were similar in persons sleeping longer or shorter duration. On the other hand auditory memory scores were significantly lower in persons accustomed to >10 h sleep. The results indicate the importance of sleep duration on episodic memory processing of learned material even during wakeful state specially which involves auditory system.

Ca2+ -free medium enhances the magnitude of slow peak in compound action potential of frog sciatic nerve in vitro.

The present investigation was carried out to know the effect of Ca2+ on different peaks of compound action potential (CAP) representing the fibers having different conduction velocity. CAP was recorded from a thin bundle of nerve fibers obtained from desheathed frog sciatic nerve. Suction electrodes were used for stimulating and recording purposes. In Ca2+ -free amphibian Ringer, two distinct peaks (Peak-I and Peak-II) were observed. The threshold, conduction velocity (CV), amplitude and duration of Peak-I were 0.32 +/- 0.02 V, 56 +/- 3.0 m/sec, 2.1 +/- 0.2 mV and 0.75 +/- 0.1 ms, respectively. The Peak-II exhibited ten times greater threshold, eight times slower CV, three times lower amplitude and four times greater duration as compared to Peak-I. Addition of 2 mM Ca2+ in the bathing medium did not alter CAP parameters of Peak-I excepting 25% reduction in CV. But, in Peak-II there was 70-75% reduction in area and amplitude. The concentration-attenuation relation of Peak-II to various concentrations of Ca2+ was nonlinear and 50% depression occurred at 0.35 mM of Ca2+. Washing with Ca2+ -free solution with or without Mg2+ (2 mM)/verapamil (10 microM) could not reverse the Ca2+ -induced changes in Peak-II. Washing with Ca2+ -free solution containing EDTA restored 70% of the response. The results indicate that Ca2+ differentially influence fast and slow conducting fibers as the activity of slow conducting fibers is greatly suppressed by external calcium.