Cough and swallow after laparotomy in anesthetized cats

An anesthetized cat animal model was used to evaluate changes in cough and swallow after a small midline upper abdominal incision (laparotomy). Two additional conditions were tested: sealing the laparotomy with gentle suctioning via a small cannula, and subsequent closure of the abdominal wall with suture. These abdominal wall manipulations resulted in no changes in the cough reflex, but produced higher motor drive to pharyngeal musculature (thyropharyngeus and geniohyoid muscles) during swallow. Swallow-breathing coordination phase preference shifted towards swallow occurring more during the inspiratory phase. There were no significant changes in cough motor pattern, or cough and swallow number and temporal features. The respiratory changes were limited to reduced inspiratory motor drive to the diaphragm. The results are consistent with an important role of sensory feedback from the abdominal wall in regulation of swallow motor pattern. The level of reflex modulation may depend on the extent of injury and likely on its position in the abdomen.

Differential inhibition of cough by GABAA and GABAB receptor antagonists in the nucleus of the solitary tract in cats

Bicuculline and saclofen were microinjected into the rostral (rNTS) and caudal nucleus of the solitary tract (cNTS) in 17 anesthetized cats. Electromyograms (EMGs) of the diaphragm (DIA) and abdominal muscles (ABD), esophageal pressures (EP), and blood pressure were recorded and analyzed. Bilateral microinjections of 1 mM bicuculline in the rNTS significantly reduced the number of coughs (CN), amplitudes of DIA and ABD EMG, inspiratory and expiratory EP, and prolonged the duration of the cough expiratory phase (CTE) as well as the total cough cycle duration (CTtot). Bilateral microinjections of 2 mM saclofen reduced only cough expiratory efforts. Bilateral microinjection of bicuculline in the cNTS significantly reduced CN and amplitudes of ABD EMG and elongated CTE and CTtot. Bilateral microinjections of saclofen in cNTS had no significant effect on analyzed cough parameters. Our results confirm a different GABAergic inhibitory system in the rNTS and cNTS acting on mechanically induced cough in cats.

Modeling and simulation of vagal afferent input of the cough reflex

We employed computational modeling to investigate previously conducted experiments of the effect of vagal afferent modulation on the cough reflex in an anesthetized cat animal model. Specifically, we simulated unilateral cooling of the vagus nerve and analyzed characteristics of coughs produced by a computational model of brainstem cough/respiratory neuronal network. Unilateral vagal cooling was simulated by a reduction of cough afferent input (corresponding to unilateral vagal cooling) to the cough network. All these attempts resulted in only mild decreases in investigated cough characteristics such as cough number, amplitudes of inspiratory and expiratory cough efforts in comparison with experimental data. Multifactorial alterations of model characteristics during cough simulations were required to approximate cough motor patterns that were observed during unilateral vagal cooling in vivo. The results support the plausibility of a more complex NTS processing system for cough afferent information than has been proposed.

Distinct modulation of tracheal and laryngopharyngeal cough via superior laryngeal nerve in cat

Unilateral and bilateral cooling and bilateral transsection of the superior laryngeal nerve (SLN) were employed to modulate mechanically induced tracheobronchial (TB) and laryngopharyngeal (LPh) cough in 12 anesthetized cats. There was little effect of SLN block or cut on TB. Bilateral SLN cooling reduced the number of LPh (<50 %, p < 0.05), amplitudes of diaphragm EMG activity (<55 %, p < 0.05), and cough expiratory efforts (<40 %, p < 0.01) during LPh. Effects after unilateral SLN cooling were less pronounced. Temporal analysis of LPh showed only shortening of diaphragm and abdominal muscles burst overlap in the inspiratory-expiratory transition after unilateral SLN cooling. Bilateral cooling reduced both expiratory phase and total cough cycle duration. There was no significant difference in the average effects of cooling left or right SLN on LPh or TB as well as no differences in contralateral and ipsilateral diaphragm and abdominal EMG amplitudes. Our results show that reduced afferent drive in the SLN markedly attenuates LPh with virtually no effect on TB.

Modulation of Cough Reflex by Gaba-Ergic Inhibition in Medullary Raphé of the Cat

We studied the effects of GABA receptor agonists microinjections in medullary raphé on the mechanically induced tracheobronchial cough response in anesthetized, unparalyzed, spontaneously breathing cats. The results suggest that GABA-ergic inhibition significantly contributes to the regulation of cough reflex by action of both GABA(A) and GABA(B) receptors. The data are consistent with inhomogeneous occurrence of GABA-ergic neurons in medullary raphé and their different involvement in the cough reflex control. Cells within rostral nucleus raphéobscurus with dominant role of GABA(A) receptors and neurons of rostral nucleus raphépallidus and caudal nucleus raphémagnus with dominant role of GABA(B) receptors participate in regulation of cough expiratory efforts. These cough control elements are distinct from cough gating mechanism. GABA-ergic inhibition in the raphé caudal to obex had insignificant effect on cough. Contradictory findings for GABA, muscimol and baclofen administration in medullary raphé suggest involvement of coordinated activity of GABA on multiple receptors affecting raphé neurons and/or the local neuronal circuits in the raphé modulating cough motor drive.

The motor pattern of tracheobronchial cough is affected by inspiratory resistance and expiratory occlusion - The evidence for volume feedback during cough expiration

The role of pulmonary stretch receptor discharge and volume feedback in modulation of tracheobronchial cough is not fully understood. The current study investigates the effect of expiratory occlusion with or without preceding inspiratory resistance (delivery of tidal or cough volume by the ventilator lasting over the active cough expiratory period) on the cough motor pattern. Experiments on 9 male cats under pentobarbital sodium anesthesia have shown that inspiratory resistance followed by expiratory occlusion increased cough inspiratory and expiratory efforts and prolonged several time intervals (phases) related to muscle activation during cough. Expiratory occlusion (at regular cough volume) decreased number of coughs, increased amplitudes of abdominal electromyographic activity, inspiratory and expiratory esophageal pressure during cough and significantly prolonged cough temporal features. Correlation analysis supported major changes in cough expiratory effort and timing due to the occlusion. Our results support a high importance of volume feedback, including that during cough expulsion, for generation and modulation of cough motor pattern with obstruction or expiratory airway resistances, the conditions present during various pulmonary diseases.

GABA-ergic neurotransmission in the nucleus of the solitary tract modulates cough in the cat

GABA, muscimol, and baclofen were microinjected into the rostral (rNTS) and caudal solitary tract nucleus (cNTS) in 24 anesthetized cats. Electromyograms (EMGs) of diaphragm (DIA) and abdominal muscles (ABD), blood pressure and esophageal pressure (EP) were recorded and analysed. Bilateral microinjections of 1 mM GABA (total 66 ± 4 nl), 1 mM baclofen (64 ± 4 nl) and unilateral microinjections of 0.5 mM muscimol (33 ± 1 nl) in the rNTS significantly reduced cough number (CN), amplitudes of ABD EMGs, expiratory EP, and prolonged the duration of the cough inspiratory phase. GABA microinjections decreased the amplitudes of cough-related DIA EMGs and inspiratory EP; muscimol microinjections decreased the cough DIA EMG on the contralateral side. Only microinjections of GABA into the cNTS suppressed CN. In some cases, microinjections prolonged the inspiratory phase, lowered respiratory rate, changed the depth of breathing, and increased blood pressure and heart rate. Our results confirm that GABA-ergic inhibitory mechanisms in the rNTS can regulate coughing in the anesthetized cat.

Role of the dorsomedial medulla in suppression of cough by codeine in cats

The modulation of cough by microinjections of codeine in 3 medullary regions, the solitary tract nucleus rostral to the obex (rNTS), caudal to the obex (cNTS) and the lateral tegmental field (FTL) was studied. Experiments were performed on 27 anesthetized spontaneously breathing cats. Electromyograms (EMG) were recorded from the sternal diaphragm and expiratory muscles (transversus abdominis and/or obliquus externus; ABD). Repetitive coughing was elicited by mechanical stimulation of the intrathoracic airways. Bilateral microinjections of codeine (3.3 or 33mM, 54±16nl per injection) in the cNTS had no effect on cough, while those in the rNTS and in the FTL reduced coughing. Bilateral microinjections into the rNTS (3.3mM codeine, 34±1 nl per injection) reduced the number of cough responses by 24% (P<0.05), amplitudes of diaphragm EMG by 19% (P<0.01), of ABD EMG by 49% (P<0.001) and of expiratory esophageal pressure by 56% (P<0.001). Bilateral microinjections into the FTL (33mM codeine, 33±3 nl per injection) induced reductions in cough expiratory as well as inspiratory EMG amplitudes (ABD by 60% and diaphragm by 34%; P<0.01) and esophageal pressure amplitudes (expiratory by 55% and inspiratory by 26%; P<0.001 and 0.01, respectively). Microinjections of vehicle did not significantly alter coughing. Breathing was not affected by microinjections of codeine. These results suggest that: 1) codeine acts within the rNTS and the FTL to reduce cough in the cat, 2) the neuronal circuits in these target areas have unequal sensitivity to codeine and/or they have differential effects on spatiotemporal control of cough, 3) the cNTS has a limited role in the cough suppression induced by codeine in cats.

Microinjection of kynurenic acid in the rostral nucleus of the tractus solitarius disrupts spatiotemporal aspects of mechanically induced tracheobronchial cough

The importance of neurons in the nucleus of the solitary tract (NTS) in the production of coughing was tested by microinjections of the nonspecific glutamate receptor antagonist kynurenic acid (kyn; 100 mM in artificial cerebrospinal fluid) in 15 adult spontaneously breathing anesthetized cats. Repetitive coughing was elicited by mechanical stimulation of the intrathoracic airway. Electromyograms (EMG) were recorded from inspiratory parasternal and expiratory transversus abdominis (ABD) muscles. Bilateral microinjections of kyn into the NTS rostral to obex [55 ± 4 nl total in 2 locations (n = 6) or 110 ± 4 nl total in 4 locations (n = 5)], primarily the ventrolateral subnucleus, reduced cough number and expiratory cough efforts (amplitudes of ABD EMG and maxima of esophageal pressure) compared with control. These microinjections also markedly prolonged the inspiratory phase, all cough-related EMG activation, and the total cough cycle duration as well as some other cough-related time intervals. In response to microinjections of kyn into the NTS rostral to the obex respiratory rate decreased, and there were increases in the durations of the inspiratory and postinspiratory phases and mean blood pressure. However, bilateral microinjections of kyn into the NTS caudal to obex as well as control vehicle microinjections in the NTS location rostral to obex had no effect on coughing or cardiorespiratory variables. These results are consistent with the existence of a critical component of the cough rhythmogenic circuit located in the rostral ventral and lateral NTS. Neuronal structures of the rostral NTS are significantly involved specifically in the regulation of cough magnitude and phase timing.NEW & NOTEWORTHY The nucleus of the solitary tract contains significant neuronal structures responsible for control of 1) cough excitability, 2) motor drive during cough, 3) cough phase timing, and 4) cough rhythmicity. Significant elimination of neurons in the solitary tract nucleus results in cough apraxia (incomplete and/or disordered cough pattern). The mechanism of the cough impairment is different from that for the concomitant changes in breathing.

The course of lung inflation alters the central pattern of tracheobronchial cough in cat-The evidence for volume feedback during cough

The effect of volume-related feedback and output airflow resistance on the cough motor pattern was studied in 17 pentobarbital anesthetized spontaneously-breathing cats. Lung inflation during tracheobronchial cough was ventilator controlled and triggered by the diaphragm electromyographic (EMG) signal. Altered lung inflations during cough resulted in modified cough motor drive and temporal features of coughing. When tidal volume was delivered (via the ventilator) there was a significant increase in the inspiratory and expiratory cough drive (esophageal pressures and EMG amplitudes), inspiratory phase duration (CTI), total cough cycle duration, and the duration of all cough related EMGs (Tactive). When the cough volume was delivered (via the ventilator) during the first half of inspiratory period (at CTI/2-early over inflation), there was a significant reduction in the inspiratory and expiratory EMG amplitude, peak inspiratory esophageal pressure, CTI, and the overlap between inspiratory and expiratory EMG activity. Additionally, there was significant increase in the interval between the maximum inspiratory and expiratory EMG activity and the active portion of the expiratory phase (CTE1). Control inflations coughs and control coughs with additional expiratory resistance had increased maximum expiratory esophageal pressure and prolonged CTE1, the duration of cough abdominal activity, and Tactive. There was no significant difference in control coughing and/or control coughing when sham ventilation was employed. In conclusion, modified lung inflations during coughing and/or additional expiratory airflow resistance altered the spatio-temporal features of cough motor pattern via the volume related feedback mechanism similar to that in breathing.

Upper Airway Control in Airway Defense

Upper airways (UA) are an organic component of the respiratory tract, they serve to respiration, respiratory tract protection and defense, phonation, deglutition, etc. The functions of UA are regulated by motor control of the oral, pharyngeal, and laryngeal muscles.

UA typically stiffen and widen during inspiration mainly due to the activation of the alae nasi, genioglossus m., pharyngeal dilators, and laryngeal abductors. These and other UA muscles (e.g. laryngeal and pharyngeal constrictors) may express varoius activity patterns, actively shaping UA depending on species, arousal, respiratory drive, and behavior being executed. E.g. during coughing and sneezing laryngeal movement consists of abductions in inspiration and expiration and adductions in compression and subsequent constriction phase. The cricopharyngeus m., in cough expiration the superior pharyngeal constrictor and in the sneeze expiration the styloglossus and levator veli palatini m. are activated. Unlike in breathing or coughing, where UA serve to respiration-protection-defense, the pharyngeal phase of swallowing is essentially made by the coordinated action of a number of UA muscles.

Motoneurons driving the UA muscles are located primarily in the hypoglossal and ambigual nuclei. Motor pattern of individual motoneuronal pools is determined by activation-inhibition-modulation from pre-motoneurons and other upstream neurons of the reflex circuits. Laryngeal and hypoglossal nerve activity is during breathing under command of respiratory central pattern generator. UA muscles are driven in inspiration primarily from augmenting, less from decrementing and constant inspiratory neurons. Number of additional inputs is involved in UA regulation during expirations and other motor behaviors. Anatomical and functional studies pointed out number of brainstem areas, such as the regions of solitary tract nucleus, hypoglossal ncl., trigeminal ncl., lateral tegmental field, raphé, the ventral and ventrolateral medulla, pontine parabrachial region, etc. with neurons related to UA motor control.

Abundant connectivity of the neuronal network that controls UA patency employs almost all kind of receptors and neurotransmitter/neuromodulator systems. Among large number of diseases and disorders that relate to UA, primarily cholinergic, norepinephrine, and serotonergic tonic drives are implicated in those resulted from the reduced UA tone. Pharmacological and frequently simple surgical interventions may improve these conditions (snore, obturation) in patients. Recently, besides medicinal treatment, conditional procedures incorporating an exercise and practice, stimulation of appropriate afferent pathways, and combining reflex responses may offer promising therapies.

Central antitussive effect of codeine in the anesthetized rabbit

Background

Codeine represents a commonly used drug to suppress cough. Central antitussive effect of codeine has been confirmed in a number of animal studies. However, available data related to antitussive activity of codeine in rabbits are very limited.

Objective

We investigated the effects of codeine on cough, single expiratory responses (expiration-like reflex) induced by mechanical tracheo-bronchial stimulation, and on the sneeze reflex in the anesthetized rabbit.

Materials and methods

Twenty pentobarbitone anesthetized spontaneously breathing rabbits were used for the study. Increasing doses of codeine (codeinum dihydrogenphosphate, Interpharm) were injected intravenously (iv); 0, 0.15, 0.76, and 3.78 mg/kg of codeine dissolved in saline, 0.25 ml/kg) or intracerebroventricularly (icv); 0, 0.015, 0.076, and 0.378 mg/kg of codeine dissolved in artificial cerebrospinal fluid, 0.033 ml/kg.

Results

Both iv and icv injections of codeine led to a dose-dependent reduction of coughing provoked by tracheo-bronchial stimulation; however, the doses differed substantially. The effective cumulative dose for a 50% reduction in the number of coughs was 3.9 and 0.11 mg/kg after iv and icv administration of codeine, respectively; representing about 35-fold higher efficacy of the icv route. The numbers of expiration-like responses and sneeze reflex responses remained unchanged.

Conclusions

The study confirmed the central antitussive effect of codeine, but showed a low sensitivity of sneeze and expiration reflex to codeine. We validated the experimental model of an anesthetized rabbit for studies on central antitussive action.

Placenta and umbilical cord blood deserve attention

OBJECTIVES

This work follows up with our already published results concerning consequences of lead on prenatal and postnatal development of child in connection with the rise of hyperkinetic syndrome (ADHD). This disease has in children increasing tendency all over the world.

METHODS

In our work we used a set of histological and histochemical methods, method of scanning electron microscopy, infrared spectroscopy and statistical evaluation.

RESULTS

Our new method for proof of lead in placenta enabled us to show how lead is cumulated in syncytiotrophoblast. We have found release of lead from mother's erythrocytes in the intervillous space and receipt of lead by erythrocytes of fetus in the vessels of the villi of placenta. This finding enriches knowledge about relation between mother's erythrocytes, lead, calcium that is lead carrier, syncytiotrophoblast, and erythrocytes of fetus in the vessels of placental villi. We have proved that syncytiotrophoblast is the most frequent place for cumulation of lead deposits. We verified our ecomorphologic results by means of infrared spectroscopy in cooperation with physicists and statistically evaluated occurrence of ADHD in particular age categories what helps to fill gaps in knowledge of ADHD etiology.

CONCLUSIONS

Our finding of lead in umbilical cord blood immediately after the child birth is forewarning against the possible rise of the ADHD. This finding facilitates early diagnostics and means preventing step against the rise, development and consequences of this disease. The obtained results give evidence about the serious influence of mother's dwelling in environment polluted with neurotoxic metal - lead on the prenatal and postnatal development of child.

Provocation of aspiration reflexes and their effects on the pattern of cough and reflex apnea in cats

Aspiration reflexes (AspRs) manifesting as reflex spasmodic inspirations and their effects on motor pattern of tracheobronchial cough and reflex apnea were studied on 22 spontaneously breathing pentobarbitone-anesthetized cats. AspRs induced during cough inspiration enhanced peak inspiratory (P<0.01) and expiratory (P<0.02) esophageal pressures, amplitudes of diaphragm (P<0.01) and abdominal muscles (P<0.05) EMG activity, and prolonged the entire expiratory period (P<0.01) and total cycle duration (P<0.05) of cough. Transient inhibitions and splits of cough expiration frequently occurred with AspR within active cough expiratory period; however, cough spatiotemporal characteristics were not altered significantly. Sub-threshold nasopharyngeal stimulation failing to provoke AspR had no significant effects on coughing. Hering-Breuer inflation apnea was moderately prolonged by AspRs (20%; P<0.05), unlike the apnea produced by continual mechanical laryngeal stimulation. AspRs are inducible during tested behaviors interacting with their motor pattern. Central mechanisms involving pulmonary stretch receptor stimulation is suggested for modulation of cough and inflation apnea by AspR.

Excitability and rhythmicity of tracheobronchial cough is altered by aspiration reflex in cats

Effects of nasopharyngeal stimulation on excitability and rhythmicity of mechanically induced tracheobronchial cough were examined on 18 pentobarbitone anesthetized cats. After the 17.2+/-2.4 aspiration reflexes (AspRs), tracheobronchial stimulation evoked lower number of coughs (P<0.05) with longer latency to the diaphragm activation (P<0.02), compared to control. AspRs induced within "inter-cough" periods (motor quiescence between individual coughs; 3.3 AspRs per period) reduced cough number by 50% (P<0.01), shortened cough-related abdominal activity (P<0.02), prolonged inter-cough period (P<0.02), and the total cough cycle duration (P<0.05). Cough efforts occurred irregularly with very variable "inter-cough" distances and total cough cycle durations. The subthreshold nasopharyngeal stimulation (failing to evoke AspR) did not affect rhythmic coughing. AspRs induced during persisting post-stimulation coughs did not significantly reduce their number. Excitability and rhythmicity of mechanically induced tracheobronchial cough can be reduced by AspRs, but not by subthreshold nasopharyngeal stimulation. The suppressive effect of spasmodic inspirations on chronic cough is suggested.