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PubMed1985

Inhibition of the swallowing reflex by local application of serotonergic agents into the nucleus of the solitary tract.

Swallowing is a medullary polysynaptic reflex organized by an interneuronal network localized mainly within the nucleus of the solitary tract (NST). The existence of several putative neurotransmitters within the NST has been well demonstrated. The presence of serotonin (5-HT) in nerve terminals and fibers has been particularly well-documented. This study was therefore designed to determine the role of 5-HT in the swallowing reflex. The effects of serotonergic agents were investigated in the rat, on rhythmic swallowing elicited by long repetitive stimulation of the superior laryngeal nerve (SLN). The agents were microinjected by pressure application, within the swallowing region of the NST. Microinjections of 5-HT (0.3-5 nmol, 30-50 nl) significantly decreased the number and the amplitude of swallows elicited by stimulation of the ipsilateral SLN without changing the swallowing reflex induced by contralateral SLN stimulation. The decrease induced by 5-HT microinjections was dose-related. No significant modification of swallowing was induced by control injections of the vehicle within the active sites. Moreover, the effect of 5-HT microinjections was significantly antagonized by pretreatment with metitepine (0.4 nmol) applied locally in the NST and microinjections of quipazine (2.5 nmol) also decreased the number of swallows. It can therefore be concluded that the present findings suggest the existence within the NST of a serotonergic inhibition of the swallowing reflex elicited by laryngeal afferents.

Animals↗
PubMed1994

Effect of continuous swallowing on respiration.

We examined the effect of continuous swallowing on breathing pattern and ventilation in 7 adult subjects. Repetitive swallowing was induced by oral infusion of water at a variable rate of 40, 60, 80 or 100 ml/min, while the subject breathed through the nose. The number of swallows increased from a mean of 5.2 (+/- 2.7 SD) swallows/min during the control period to 9.2 +/- 2.0 to 13.7 +/- 2.9 swallows/min during infusion of 40 and 100 ml/min, respectively. The duration of interruption of breathing was bolus volume-dependent, increasing from 0.55 +/- 0.09 sec with a mean bolus volume of 4.6 +/- 1.4 ml to 0.87 +/- 0.23 sec with a bolus volume of 8.1 +/- 1.9 ml. The majority of swallows (73 +/- 12%) interrupted breathing during inspiration. The mean tidal volume, inspiratory and expiratory times during swallowing periods were higher than those recorded during the control period, but the mean level of ventilation was not different from control, at all swallowing frequencies. Repetitive swallowing did not result in a single incidence of aspiration or coughing. We conclude that mechanisms integrating breathing and swallowing allow repetitive swallowing to occur without compromising ventilation, and that these mechanisms perfectly orchestrate between breathing and deglutition to prevent aspiration.

Adult↗
PubMed2004

Comparison of tongue functions between mature and tongue-thrust swallowing--an ultrasound investigation.

Many studies have proved that tongue thrusting plays a significant role in the etiology of some orofacial deformities. To learn more about the relationship between tongue function and the form of orofacial structures, it is important to recognize patients with abnormal swallowing patterns. A cushion scanning technique in combination with M-mode ultrasound was applied to measure and compare tongue movements between mature swallowing and tongue-thrust swallowing. Forty subjects with a mature swallowing pattern (23 female, 17 male, aged 21.8 +/- 6.1 years) and 15 subjects with a tongue-thrust swallowing pattern (8 female, 7 male, aged 13.6 +/- 6.6 years) were included in this study. Duration, range, speed, and reproducibility for each of the swallowing subphases were calculated and compared. Tongue-thrust swallowers had a longer late transport phase than mature swallowers (P <.0009), and the tongue speed was faster in the early final phase (P <.05) compared with mature swallowers. Distinctly different movements can be positively differentiated with the method used.

Adolescent↗
PubMed2004

Acoustic study of swallowing behaviour in premature infants during tube-bottle feeding and bottle feeding period.

The premature infant has limited ability to integrate the swallowing-breathing cycle during feeding. The aim of this study was to assess the pattern of swallowing between the period of tube-bottle (TBF) and bottle (BF) feeding by means of cervical auscultation in premature infants. Twenty-three premature infants were enrolled (mean gestational age 34.7 +/- 1.7 weeks). Audiosignal recordings were made during TBF and BF with a small microphone set in front of the cricoid cartilage. The following parameters were calculated for 2 min and reported at 1 min: the percentage of time involved in swallowing (ST), the numbers of swallows (SN) and swallowing bursts (SB) and swallowing groups (SG). Individual histograms were established to show the individual pattern of swallowing behaviour and the distribution of groups, bursts and swallows over 2 min. Mean (STm), (SNm), (SBm), (SGm) values were calculated (+/- S.D.). Statistical analysis was used to compare the means and to establish correlations between parameters and curves. (STm), (SNm) and (SBm) increased significantly during BF compared with TBF for all premature infants and during follow-up. The histograms showed that in BF the groups were high in bursts. These findings and the histograms for each infant will allow determination of transition to bottle feeding without risk corresponding to the stage of maturation of swallowing function.

Auscultation↗
PubMed1997

Mastication and swallowing in patients with postirradiation xerostomia.

PURPOSE: Very little objective data has been reported on mastication and swallowing in xerostomic patients, which would substantiate presumed causal relationships between xerostomia and patient complaints. The purpose was to elucidate which components of mastication and swallowing were abnormal, and most directly related to xerostomia, and which appeared unaffected. METHODS AND MATERIALS: A retrospective analysis of timing events in mastication and swallowing was done using videofluoroscopic data for 15 cancer patients with xerostomia, and 20 normal controls. Scintigraphy was also used to determine oropharyngeal residue after a water swallow. Cancer treatment modalities included radiation therapy or chemoradiation therapy. RESULTS: For barium liquid and paste substances, timing measures were equivalent for controls and patients. Xerostomic patients took 46% longer to masticate a shortbread cookie, and timing for the initiation of swallowing was shorter, but duration of swallowing appeared unaffected. Oral and pharyngeal residues following the swallow were greater in the patient group. CONCLUSIONS: Xerostomia primarily affected mastication and oral manipulation of a dry, absorbent food material. Increased oral and pharyngeal residues after a water swallow are ambiguously related to xerostomia. The initiation and duration of the pharyngeal swallow was not abnormal.

Aged↗
PubMed2026

Characterizing Submental Neuromuscular Activity of Swallowing Rehabilitation: An Electromyographic Evaluation of Rehabilitative Maneuvers in Healthy Adults.

PURPOSE: The effortful swallow (ES), the Mendelsohn maneuver (MM), and isometric tongue presses (TPs) are widely used swallowing maneuvers/exercises to improve elements of swallowing, such as muscle strength and biomechanics. However, the underlying neuromuscular mechanisms of these exercises remain unclear, potentially limiting our ability to specify treatment targets and improve treatment efficacy. This study aimed to compare submental neuromuscular activation patterns during the ES, MM, TPs, and typical swallows in healthy young and older adults. METHOD: As part of a larger randomized crossover validation study, 60 healthy adults (30 young and 30 older) completed typical swallows and three maneuvers using a wearable submental surface electromyographic (sEMG) system (i-Phagia). Outcome variables included (a) normalized mean sEMG amplitude and (b) time to peak sEMG amplitude. Linear mixed models were used to examine effects of task, age, and sex on both outcomes. RESULTS: Normalized mean amplitude was significantly different across tasks. Post hoc pairwise comparisons confirmed that all three maneuvers produced higher normalized mean sEMG amplitude than typical swallows, with the ES eliciting the highest amplitude across age groups. Time to peak amplitude differed significantly across tasks, with typical swallows requiring the shortest time to reach peak amplitude, followed by the ES, MM, and TP. CONCLUSIONS: The ES required the highest neuromuscular effort with the shortest time to reach peak amplitude, suggesting its potential for targeting submental muscle power. Typical swallows required the least neuromuscular effort with the shortest time to reach peak amplitude, suggesting their potential for training submental muscle speed. The MM and TP may also improve submental muscle strength; however, given their temporal requirements (longer durations), they may be more beneficial for targeting coordination and endurance, though more research in this area is warranted. These findings underscore the importance of task-specific neuromuscular profiling to inform mechanism-based swallowing rehabilitation. SUPPLEMENTAL MATERIAL: https://doi.org/10.23641/asha.32948549.

Humans↗
PubMed2000

Temporal and biomechanical characteristics of oropharyngeal swallow in younger and older men.

As the U.S. population ages, there is increasing need for data on the effects of aging in healthy elderly individuals over age 80. This investigation compared the swallowing ability of 8 healthy younger men between the ages of 21 and 29 and 8 healthy older men between the ages of 80 and 94 during two swallows each of 1 ml and 10 ml liquid. Videofluoroscopic studies of these swallows were analyzed to confirm the absence of swallowing disorders. Biomechanical analysis of each swallow was completed, from which data on temporal, range of motion, and coordination characteristics of the oropharyngeal swallow were taken. Position of the larynx at rest, length of neck, and pattern of hyoid bone movement were also compared between the two groups. None of the younger or older men exhibited any swallowing disorders. The C2 to C4 distance of older men was significantly shorter than that of younger men, and laryngeal position at rest was lower than in younger men but not significantly so. Older men had a significantly longer pharyngeal delay than younger men and significantly faster onset of posterior pharyngeal wall movement in relation to first cricopharyngeal opening. The older men exhibited significantly reduced maximum vertical and anterior hyoid movement as compared to the younger men even when accounting for the difference in C2 to C4 distance in older men. These data support the hypothesis of reduced muscular reserve in the swallows of older men as compared to younger men. Older men also exhibited less width of cricopharyngeal opening than younger men at 10 ml volume, indicating less upper esophageal sphincter flexibility in the swallows of older men. The potential for exercise to improve reserve is discussed. Significant changes in extent of hyoid elevation and duration of cricopharyngeal opening were seen as liquid bolus volume increased.

Adult↗
PubMed2002

Prevalence of impaired swallowing in institutionalized older people in taiwan.

OBJECTIVES: To investigate the prevalence of impaired swallowing in residents at long-term care facilities (LTCFs) in Taiwan. DESIGN: A chart review, a structured questionnaire completed at interview, a neurological examination, and a timed swallowing test were used to assess impairment and to gather demographic data. SETTING: Nine skilled nursing facilities and nine intermediate-care facilities in metropolitan Taipei. PARTICIPANTS: One thousand two hundred twenty-one conscious and unconscious residents with a mean age of 77.07. MEASUREMENTS: Impaired swallowing was defined when a subject met two or more of the following criteria: self-report of swallowing difficulty, a score of 2 or more derived from a swallowing questionnaire combined with a neurological examination investigating symptoms and signs of impairment, and coughing/choking during a timed swallowing test or a measured swallowing rate (volume swallowed per second) below the 10th percentile as derived from a gender-based study of an older community in Taipei. RESULTS: Of the 1,221 subjects, 356 (29.2%) were fed by tube. The prevalence rates for impaired swallowing as estimated were 97.5% and 31.9% for tube-fed and non-tube-fed subjects respectively, whereas the overall prevalence for tube-fed and non-tube-fed subjects altogether was 51.0%. CONCLUSIONS: The findings may serve to increase awareness of this problem among healthcare professionals in LTCFs. Further research is contemplated to investigate whether early identification makes a difference in treatment choices and outcomes.

Aged↗
PubMed1999

Effect of uvulopalatopharyngoplasty and genial and hyoid advancement on swallowing in patients with obstructive sleep apnea syndrome.

OBJECTIVE: Uvulopalatopharyngoplasty (UPPP) and genial and hyoid advancement (GHA) are surgical techniques for the treatment of obstructive sleep apnea. These techniques enlarge the oropharyngeal and hypopharyngeal airway, reducing collapse at these levels. This study evaluated the effect of these procedures on swallowing. METHODS: Fifteen patients who had undergone UPPP and GHA were evaluated with a modified barium swallow to assess biomechanical changes in swallowing. Specifically, velopharyngeal insufficiency; changes in tongue-base movement, laryngeal elevation, and closure; epiglottic movement; and pharyngoesophageal opening were examined. A brief swallowing questionnaire was administered to assess for subjective changes in swallowing. RESULTS: Nine of 15 patients demonstrated abnormal objective swallow, of whom 5 reported normal subjective swallowing. Six of 15 demonstrated normal objective swallowing. Of these, 5 reported subjective change. CONCLUSION: UPPP with GHA may alter biomechanical events during deglutition. However, little correlation exists between subjective symptoms and objective findings. Further studies that include preoperative and postoperative modified barium swallows are needed to identify a cause-and-effect relationship.

Adult↗
PubMed1990

Swallowing dysfunction in nephropathic cystinosis.

BACKGROUND: Nephropathic cystinosis causes renal failure in most patients at approximately 10 years of age. This can be prevented or retarded by cystine-depleting therapy with oral cysteamine. Many patients who do not receive adequate cysteamine therapy undergo renal transplantation, but the accumulation of cystine continues in other organs, resulting in various clinical abnormalities. We report age-related swallowing dysfunction in patients with nephropathic cystinosis. METHODS: We studied 43 patients with cystinosis (24 who had received a renal transplant and 19 who had not), 3 to 31 years of age. Oral motor function was assessed by a cranial-nerve oral sensorimotor examination, and an oral motor index was calculated for each patient. The oral phase of swallowing was assessed by ultrasonography, and the pharyngeal and esophageal phases were evaluated by videofluoroscopy. RESULTS: Approximately half the patients were slow eaters. Oral motor dysfunction, reflected by a higher oral motor index, increased with age. Speech, oral structure and anatomy, and tongue and lip strength were particularly affected. Seven of nine patients 21 to 31 years old had abnormalities in all three phases of swallowing; the deficits were variable in younger patients. In 28 patients with cystinosis, the mean (+/- SD) duration of oropharyngeal swallowing for a dry swallow (3.06 +/- 1.06 seconds) was longer than in 14 normal subjects (1.89 +/- 0.57 seconds; P less than 0.001). This prolongation reflected impairment of the initiation phase of swallowing. CONCLUSIONS: Swallowing dysfunction is a late complication of nephropathic cystinosis, probably related to muscular dysfunction. Changes in the consistency of foods, swallowing exercises, and long-term cysteamine therapy should be considered for patients with cystinosis who have difficulty in swallowing.

Adolescent↗
PubMed2006

Effects of three different swallow maneuvers analyzed by videomanometry.

PURPOSE: To evaluate the manometric effects of three different swallow maneuvers on healthy volunteers. MATERIAL AND METHODS: Ten healthy volunteers with no history of swallowing complaints were evaluated with simultaneous videoradiography and pharyngeal manometry (videomanometry). Three different swallow maneuvers were evaluated (supraglottic swallow, super-supraglottic swallow, and Mendelsohn's maneuver) and seven manometric and two videoradiographic variables were analyzed. RESULTS: The supraglottic swallow showed a significantly weaker peak contraction of the upper esophageal sphincter (UES). The super-supraglottic swallow had a significantly higher UES relaxation pressure and the Mendelsohn maneuver a significantly higher UES peak contraction. With the Mendelsohn maneuver, there was also a significantly longer duration of the pharyngeal contraction and a significantly weaker UES peak contraction. Both the super-supraglottic and the Mendelsohn maneuver had a significantly longer bolus transit time. CONCLUSION: Our study did not show any significant difference in the relaxation duration of any of the swallowing maneuvers compared to a control swallow. With the Mendelsohn maneuver, we found that both the pharyngeal peak contraction and contraction duration were increased, which might result in an improved propulsion of bolus into the esophagus.

Adult↗
PubMed1996

Clinical measurement of swallowing in health and in neurogenic dysphagia.

We studied clinical features potentially related to dysphagia and three indices from a timed test of swallowing--average volume per swallow (ml), average time (s) per swallow and swallowing capacity (ml/s)--in 181 screened healthy adults and 30 patients with motor neurone disease (MND). In healthy adults, age, sex and height accounted for 44.3% and 55.6% of the variance of log average volume per swallow and log swallowing capacity, respectively. Symptoms and signs were more prevalent in the MND group and were associated with reduced swallowing capacity and reduced average volume per swallow; repeatability studies on these two indices in both groups showed that the median difference between the mean of two recordings on successive days and the mean of all recordings (6-15 over 3 days) was < 5% (maximum third quartile 12.8%, indices expressed as percent predicted according to age and sex). Using this simple bedside test, swallowing function can be quantified on a ratio scale and expressed as percent of that predicted by age and sex; such information may improve the predictive value of clinical assessment and provides a practical way of monitoring change in patients with dysphagia.

Adolescent↗
PubMed1992

Priming doses of atracurium and vecuronium depress swallowing in humans.

The administration of low doses of muscle relaxant may cause peripheral muscular weakness including difficulty in swallowing. In the present study, the effect of priming doses of atracurium and vecuronium on swallowing was studied. Sixty patients undergoing elective surgery under general anesthesia were divided randomly into four groups of 15 patients and received as a priming dose either vecuronium (10 or 15 micrograms/kg) or atracurium (50 or 75 micrograms/kg). Swallowing muscle activity was measured by electromyography using submental surface electrodes. Swallowing was initiated by administration of 0.3 ml distilled water through an oral catheter. Swallowing reflex was determined by measuring the latency time (i.e., time from water administration to start of EMG activity of glossal muscles). Swallowing activity was determined by integration of the EMG of glossal muscles during swallowing. Peripheral muscle strength was determined by hand grip strength. Swallowing reflex activity and peripheral muscle strength were measured before and 3 and 6 min after administration of vecuronium or atracurium. Latency time remained unchanged after any of the priming doses. Integrated EMG decreased significantly (P < .001) 3 and 6 min after all priming doses tested (42-75% of baseline value). Only after atracurium 75 micrograms/kg was the hand grip strength significantly decreased (P < .01). These results suggest that owing to its effect on swallowing, the priming dose should be used with caution.

Adult↗
PubMed1996

The swallowing side effects of botulinum toxin type A injection in spasmodic dysphonia.

Botulinum toxin type A (BOTOX) injection of the thyroarytenoid muscle is used to control speech symptoms in patients with adductor spasmodic dysphonia. Transient difficulty in swallowing liquids is a common treatment side effect. Laryngeal movement durations were measured during swallowing in 13 adductor spasmodic dysphonia patients undergoing treatment and in 6 normal control subjects in order to determine the following: 1. whether, prior to the injection, laryngeal movement durations were longer in the spasmodic dysphonia patients than in the control subjects; 2. whether movement durations increased following the injections; 3. whether preinjection swallowing difficulties related to postinjection swallowing measurements and postinjection patient reports of swallowing problems. A piezoelectric movement transducer was shown to be accurate for noninvasive measurement of laryngeal movement duration in relation to muscle onset and offset for hyoid elevation and relaxation. Before botulinum toxin type A injection, no significant differences in swallowing duration were found between the patient and control groups. Four patients with swallowing complaints prior to injection had longer laryngeal movement durations than the other spasmodic dysphonia patients and the control subjects. Following injection, laryngeal movement durations increased in the patients with spasmodic dysphonia, and eight patients reported dysphagia for an average of 2 weeks. Relationships were found between the patients' initial reports of swallowing problems and increased laryngeal movement durations before and after botulinum toxin type A injection. Those patients initially reporting swallowing difficulties had severe dysphagia for 2 weeks after the injection. Patient reports of dysphagia prior to injection may indicate a greater likelihood of significant dysphagia following thyroarytenoid injection with botulinum toxin type A.

Adult↗
PubMed2006

Sword swallowing and its side effects.

OBJECTIVE: To evaluate information on the practice and associated ill effects of sword swallowing. DESIGN: Letters sent to sword swallowers requesting information on technique and complications. SETTING: Membership lists of the Sword Swallowers' Association International. PARTICIPANTS: 110 sword swallowers from 16 countries. RESULTS: We had information from 46 sword swallowers. Major complications are more likely when the swallower is distracted or swallows multiple or unusual swords or when previous injury is present. Perforations mainly involve the oesophagus and usually have a good prognosis. Sore throats are common, particularly while the skill is being learnt or when performances are too frequent. Major gastrointestinal bleeding sometimes occurs, and occasional chest pains tend to be treated without medical advice. Sword swallowers without healthcare coverage expose themselves to financial as well as physical risk. CONCLUSIONS: Sword swallowers run a higher risk of injury when they are distracted or adding embellishments to their performance, but injured performers have a better prognosis than patients who suffer iatrogenic perforation.

Adolescent↗
PubMed2001

Electrophysiological evaluation of oropharyngeal swallowing in myotonic dystrophy.

OBJECTIVE: Oropharyngeal dysphagia is a common feature of patients with myotonic dystrophy and is not usually perceived due to their emotional deficits and lack of interest. The aim was to show the existence and frequency of subclinical electrophysiological abnormalities in oropharyngeal swallowing and to clarify the mechanisms of dysphagia in myotonic dystrophy. METHODS: Eighteen patients with myotonic dystrophy were examined for oropharyngeal phase of swallowing by clinical and electrophysiological methods. Ten patients had dysphagia whereas 11 patients had signs and symptoms reflecting CNS involvement. Four patients with myotonia congenita and 30 healthy volunteers served as controls. Laryngeal movements were detected by means of a piezoelectric sensor. EMG activities of the submental muscle (SM-EMG) and needle EMG of the cricopharyngeal muscle of the upper eosophageal sphincter (CP-EMG) were also recorded during swallowing. RESULTS: In about 70% of the patients with myotonic dystrophy, the existence of oropharyngeal dysphagia was indicated objectively by means of the technique of "dysphagia limit" and by clinical evaluation. Duration of the swallowing reflex as defined by the laryngeal relocation time (0-2 time interval) and submental muscle excitation as a part of the swallowing reflex (A-C interval) were significantly prolonged in patients with myotonic dystrophy, especially in dysphagic patients. Triggering time of the swallowing reflex (A-0 interval) also showed significant prolongation, especially in the patients having both dysphagia and CNS involvement. During swallowing, CP muscle activity was abnormal in 40% of the patients with myotonic dystrophy. CONCLUSION: Both myopathic weakness and myotonia encountered in oropharyngeal muscles play an important part in the oral and the pharyngeal phases of swallowing dysfunction in myotonic dystrophy. It was also suggested that CNS involvement might contribute to the delay of the triggering of the swallowing reflex and some abnormal EMG findings in the CP sphincter, resulting in oropharyngeal dysphagia in myotonic dystrophy.

Adult↗
PubMed1996

Pharyngeal swallowing elicited by fluid infusion: role of volition and vallecular containment.

Nonalimentary swallows minimize aspiration by clearing accumulated fluid from the pharynx. This study aimed to define 1) the pharyngeal sensory field to elicit swallowing and 2) the effect of infusion rate, volition, taste, and temperature on pharyngeal swallows. Test solutions were directed into the valleculae at 6.5, 11.5, and 32 ml/min through a catheter in eight healthy volunteers. Deglutition was signaled with electromyography and electroglottography. Spatial distribution of infusate before swallowing was studied using videofluoroscopy coupled with a video timer. Volitional control was assessed with rapid or restrained swallows. Pharyngeal swallow latency decreased as the instillation rate increased, was potently modified with volition, and was unchanged by infusate taste or temperature. Water infusion into the valleculae did not trigger pharyngeal swallowing until liquids overflowed and reached the aryepiglottic folds or pyriform sinuses. The variation in swallow latency among flow rates was mainly due to the duration of liquid containment within the valleculae. This suggests that the valleculae act to contain pharyngeal secretions and residue and prevent aspiration by diverting their contents around the larynx before swallowing.

Adult↗
PubMed2004

Central angiotensin II AT1 receptors mediate fetal swallowing and pressor responses in the near-term ovine fetus.

Swallowed volumes in the fetus are greater than adult values (per body weight) and serve to regulate amniotic fluid volume. Central ANG II stimulates swallowing, and nonspecific ANG II receptor antagonists inhibit both spontaneous and ANG II-stimulated swallowing. In the adult rat, AT1 receptors mediate both stimulated drinking and pressor activities, while the role of AT2 receptors is controversial. As fetal brain contains increased ANG II receptors compared with the adult brain, we sought to investigate the role of both AT1 and AT2 receptors in mediating fetal swallowing and pressor activities. Five pregnant ewes with singleton fetuses (130 +/- 1 days) were prepared with fetal vascular and lateral ventricle (LV) catheters and electrocorticogram and esophageal electromyogram electrodes and received three studies over 5 days. On day 1 (ANG II), following a 2-h basal period, 1 ml artificial cerebrospinal fluid (aCSF) was injected in the LV. At time 4 h, ANG II (6.4 microg) was injected in the LV, and the fetus was monitored for a final 2 h. On day 3, AT1 receptor blocker (losartan 0.5 mg) was administered at 2 h, and ANG II plus losartan was administered at 4 h. On day 5, AT2 receptor blocker (PD-123319; 0.8 mg was administered at 2 h and ANG II plus PD-123319 at 4 h. In the ANG II study, LV injection of ANG II significantly increased fetal swallowing (0.9 +/- 0.1 to 1.4 +/- 0.1 swallows/min; P < 0.05). In the losartan study, basal fetal swallowing significantly decreased in response to blockade of AT1 receptors (0.9 +/- 0.1 to 0.4 +/- 0.1 swallows/min; P < 0.05), while central injection of ANG II in the presence of AT1 receptor antagonism did not increase fetal swallowing (0.6 +/- 0.1 swallows/min). In the PD-123319 study, basal fetal swallowing did not change in response to blockade of AT2 receptor (0.9 +/- 0.1 swallows/min), while central injection of ANG II in the presence of AT2 blockade significantly increased fetal swallowing (1.5 +/- 0.1 swallows/min; P < 0.05). ANG II caused significant pressor responses in the control and PD-123319 studies but no pressor response in the presence of AT1 blockade. These data demonstrate that in the near-term ovine fetus, AT1 receptor but not AT2 receptors accessible via CSF contribute to dipsogenic and pressor responses.

Angiotensin II↗