Preoperative word-finding difficulties in children with posterior fossa tumours: a European cross-sectional study.

PURPOSE: Posterior fossa tumour surgery in children entails a high risk for severe speech and language impairments, but few studies have investigated the effect of the tumour on language prior to surgery. The current crosslinguistic study addresses this gap. We investigated the prevalence of preoperative word-finding difficulties, examined associations with medical and demographic characteristics, and analysed lexical errors. METHODS: We included 148 children aged 5-17 years with a posterior fossa tumour. Word-finding ability was assessed by means of a picture-naming test, Wordrace, and difficulties in accuracy and speed were identified by cut-off values. A norm-based subanalysis evaluated performance in a Swedish subsample. We compared the demographic and medical characteristics of children with slow, inaccurate, or combined slow and inaccurate word finding to the characteristics of children without word-finding difficulties and conducted a lexical error analysis. RESULTS: Thirty-seven percent (n = 55) presented with slow word finding, 24% (n = 35) with inaccurate word finding, and 16% (n = 23) with both slow and inaccurate word finding. Children with posterior fossa tumours were twice as slow as children in the norming sample. Right-hemisphere and brainstem location posed a higher risk for preoperative word-finding difficulties, relative to left-hemisphere location, and difficulties were more prevalent in boys than in girls. The most frequent errors were lack of response and semantically related sideordinated words. CONCLUSION: Word-finding difficulties are frequent in children with posterior fossa tumours, especially in boys and in children with right-hemisphere and brainstem tumours. Errors resemble those observed in typical development and children with word-finding difficulties.

Effect of Selected Music Soundtracks on Cardiac Vagal Control and Complexity Assessed by Heart Rate Variability.

Listening to music is experimentally associated with positive stress reduction effect on human organisms. However, the opinions of therapists about this complementary non-invasive therapy are still different. PURPOSE: The aim of our study was to investigate the effect of selected passive music therapy frequencies without vocals on selected cardio-vagal and complexity indices of short-term heart rate variability (HRV) in healthy youth, in terms of calming the human. MAIN METHODS: 30 probands (15 male, averaged age: 19.7+/-1.4 years, BMI: 23.3+/-3.8 kg/m2) were examined during protocol (Silence baseline, Music 1 (20-1000 Hz), Silence 1, Music 2 (250-2000 Hz), Silence 2, Music 3 (1000-16000 Hz), and Silence 3). Evaluated HRV parameters in time, spectral, and geometrical domains represent indices of cardio-vagal and emotional regulation. Additionally, HRV complexity was calculated by approximate entropy and sample entropy (SampEn) and subjective characteristics of each phase by Likert scale. RESULTS: the distance between subsequent R-waves in the electrocardiogram (RR intervals [ms]) and SampEn were significantly higher during Music 3 compared to Silence 3 (p=0.015, p=0.021, respectively). Geometrical cardio-vagal index was significantly higher during Music 2 than during Silence 2 (p=0.006). In the subjective perception of the healthy youths evaluated statistically through a Likert scale, the phases of music were perceived significantly more pleasant than the silent phases (p<0.001, p=0.008, p=0.003, respectively). CONCLUSIONS: Our findings revealed a rise of cardio-vagal modulation and higher complexity assessed by short-term HRV indices suggesting positive relaxing effect music especially of higher frequency on human organism.

Electromagnetic fields - do they pose a cardiovascular risk?

Mobile wireless communication technologies have now become an everyday part of our lives, 24 hours a day, 7 days a week. Monitoring the autonomous system under exposition to electromagnetic fields may play an important role in broading of our still limited knowledge on their effect on human body. Thus, we studied the interaction of the high frequency electromagnetic field (HF EMF) with living body and its effect on the autonomic control of heart rate using Heart Rate Variability (HRV) linear and nonlinear analyses in healthy volunteers. A group of young healthy probands (n=30, age mean: 24.2 ± 3.5 years) without any symptoms of disease was exposed to EMF with f=2400 MHz (Wi Fi), and f=2600 MHz (4G) for 5 minutes applied on the chest area. The short-term heart rate variability (HRV) metrics were used as an indicator of complex cardiac autonomic control. The evaluated HRV parameters: RR interval (ms), high frequency spectral power (HF-HRV in [ln(ms2)]) as an index of cardiovagal control, and a symbolic dynamic index of 0V %, indicating cardiac sympathetic activity. The cardiac-linked parasympathetic index HF-HRV was significantly reduced (p =0.036) and sympathetically mediated HRV index 0V % was significantly higher (p=0.002) during EMF exposure at 2400 MHz (Wi-Fi), compared to simulated 4G frequency 2600 MHz. No significant differences were found in the RR intervals. Our results revealed a shift in cardiac autonomic regulation towards sympathetic overactivity and parasympathetic underactivity indexed by HRV parameters during EMF exposure in young healthy persons. It seems that HF EMF exposure results in abnormal complex cardiac autonomic regulatory integrity which may be associated with higher risk of later cardiovascular complications already in healthy probands.

Radiofrequency electromagnetic field affects heart rate variability in rabbits.

The aim of this study was to assess the effects of radiofrequency electromagnetic field (RF EMF) on heart rate variability (HRV) in rabbits with intensity slightly exceeding the limits for occupations. Totally 21 New Zealand white rabbits divided into two groups were used in this double-blind study. The first group of animals without general anesthesia was subjected to HRV examination under exposure to a device generated RF EMF source (frequency 1788 MHz, intensity 160 V/m, lasting 150 min.). The second group (premedications + alpha chloralose mg/kg) underwent the same protocol under the exposure to the real RF EMF signal from the base stations of mobile providers (frequency range 1805 - 1870 MHz - corresponding to the downlink signal of Slovak mobile providers, 160 V/m, 150 min., respectively). Individual 5 min records were used to analyze the HRV parameters: heart rate and root Mean Square of the Successive Differences (rMSSD) for time domain analysis and spectral powers in the low (LF-VFS) and high frequency (HF-VFS) bands for frequency domain analysis. Our study revealed the increased in HRV parameters (HF-HRV, rMSSD) associated with lower heart rate indicating increased cardiac vagal control under the exposure to RF EMF in experimental methods.

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 impact of sound exposure on heart rate variability in adolescent students.

Previous studies of physiological responses to music and noise showed the effect on the autonomic nervous system. The heart rate variability (HRV) has been used to assess the activation of the sympathetic and the parasympathetic nervous systems. The present study was aimed to examine HRV with exposure to four sine-wave pure tones (20 Hz, 50 Hz, 2 kHz and 15 kHz) in an environment where the sound intensity exceeded level 65 dB (A-weighted). The participants (20 adolescent girls) were lying in supine position during exposure protocol divided into 6 periods, the first time with generated sounds and the second time without sounds. In the protocol without sound exposure, the low frequency band of the HRV spectrum was increased compared to the basal state before examination (period_1: 6.05+/-0.29 ms(2) compared to period_5: 6.56+/-0.20 ms(2), p<0.05). The significant increase of root Mean Square of the Successive Differences (rMSSD, period_1: 4.09+/-0.16 s compared to period_6: 4.33+/-0.12 s, p<0.05) and prolongation of R to R peak (RR) interval (period_1: 889+/-30 ms compared to period_5: 973+/-30 ms, p<0.001) were observed in the protocol without sound exposure comparing to the protocol with sound exposure where only bradycardia was observed. Contrary to rather polemical data in literature our pilot study suggests that sounds (under given frequencies) have no impact on the heart rate variability and cardiac autonomic regulation.

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 ±â€¯4 nl), 1 mM baclofen (64 ±â€¯4 nl) and unilateral microinjections of 0.5 mM muscimol (33 ±â€¯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.

Iron deposition in rabbit cerebellum after exposure to generated and mobile GSM electromagnetic fields.

BACKGROUND: Mobile phone application may cause structural, functional changes and accumulation of toxic elements in brain. OBJECTIVES: The aim of this study was to investigate iron accumulation in rabbit cerebellum after exposure to RF EMF with light and scanning electron microscopy. MATERIALS AND METHODS: Histochemical analysis of iron distribution by light and electron microscopy with energy-dispersive microanalysis was used. RESULTS: Light microscopy revealed dystrophic changes of Purkinje cells in irradiated groups and iron deposits located in various parts of cerebellum. Deposits consists of C, O, Na, Mg, Al, Si, P, S, Cl, Ca and Fe. CONCLUSION: Our experiment revealed structural changes of Purkinje cells and iron and aluminium accumulations in stratum granulosum of rabbit's cerebellum after exposure to RF EMF (Fig. 6, Ref. 33).

Differential effects of kainic acid lesions in medullary raphe on cough and sneeze in anesthetized rabbits.

The effects of microinjections of the excitatory neurotoxin kainic acid (2 mg/ml; 49 ± 1 nl) on the mechanically induced tracheobronchial cough, sneeze, and solitary expulsions from the trachea were examined in 11 anesthetized rabbits. Kainic acid was injected into the medulla (1.6-2.8 mm rostral to the obex, 1.4-1.6 and 2.9-3.2 mm below the dorsal medullary surface). Blood pressure, esophageal pressure (EP), and electromyograms (EMGs) of the diaphragm (DIA) and abdominal muscles (ABD) were recorded. Kainic acid reduced the number of coughs (means ± SE) from 3.8 ± 2.0 to 0.9 ± 0.7 (p = 0.016), the amplitude of DIA cough from 90 ± 11 to 42 ± 13 % (p = 0.004), ABD EMG moving average from 103 ± 9 to 37 ± 15 % (p = 0.006), and inspiratory from 0.67 ± 0.13 to 0.36 ± 0.12 kPa (p = 0.013) and expiratory EP from 1.70 ± 0.54 to 0.89 ± 0.46 kPa (p = 0.008). Kainic acid had no effect on the number of sneeze reflexes nor did it affect solitary expulsions from the trachea. These effects were accompanied by significant increases in systemic blood pressure and respiratory rate. Spatiotemporal analysis of the cough and sneeze reflexes revealed increases in the duration of cough active expiratory phase, in the intervals between maxima of DIA and ABD EMG discharges, and in the active portion of total cough phase duration. Our findings suggest a diverse role of raphe neurons in the central control of motor airway responses such as coughing and sneezing. A complex function of raphe neurons in the generation of the cough motor pattern also is suggested.

Integration of simulated multipotential signals: the role of integration window width and of the number of spikes.

Electrical signals recorded from nerves/muscles represent the fundamentals for experimental data analysis including an assessment of respiratory motor output. The present work, based on theoretical model, is focused on the linearity and variability of rectified and integrated electroneurogram (ENG)/electromyogram (EMG) signals in relation to the frequency of spike incidence and moving average window width used for processing of signals. Our simulations of multipotential signals (multiunit action potentials) originating from an overlapping of four single units with phase shifts firing at two frequencies demonstrates that (1) integrated ENG/EMG signals are only approximately linearly proportional to the frequency of action potentials in the superposition - multipotential and (2) the width of the moving average window strongly influences the range (dispersion) of integrated values. Better quality of EMG recordings, a higher number of action potentials within the multipotential signals, and a wider width of the moving average window increase the accuracy of integrated ENG/EMG values during processing of motor output signals.

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. MATERIAL 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.

Intranasal TRPV1 agonist capsaicin challenge and its effect on c-fos expression in the guinea pig brainstem.

Central neuronal interaction seems to play a role in pathogenesis of upper airway cough syndrome. In the guinea pig model we used the method c-fos expression to identify neurons involved in processing of nociceptive nasal stimuli and their contribution to enhancement of cough. 21 spontaneously breathing, urethane anaesthetized animals were used. The controls received intranasal saline, stimulation group received capsaicin (15 microl, 50 microM), and not-treated group was free of nasal challenge. After 2 h animals were deeply anaesthetized, exsanguinated and transcardially perfused with saline and paraformaldehyde. The brainstems were removed, post-fixed, and slices were processed immunohistochemically for c-fos. In capsaicin group the FLI was detected in the nTs 0.5 mm caudal, 1.5 mm lateral to the obex, the area postrema, LRN and VRG. Intensive FLI was identified in trigeminal nuclear complex. Mean number of FOS positive neurons per section was significantly higher in capsaicin group than that in no-treatment controls or saline controls at the level of obex (p<0.01). Neurons of nTs and VRG clearly activated after nasal provocation may participate in enhancement of cough.

Distinct generators for aspiration and expiration reflexes: localization, mechanisms and effects.

Re-evaluation of our earlier c-Fos-like immuno-reactive studies and brainstem transection/lesion experiments in over 40 anaesthetized, non-paralyzed cats allowed comparison of two distinct airway defensive reflexes with the distinct generators for inspiration (I) and expiration (E), described recently in juvenile rats. The spiration reflex (AspR) is characterized by solitary rapid and strong inspiratory effort with a reciprocal inhibition, preventing a subsequent active expiration, while the expiration reflex (ExpR) manifests by rapid and strong expiratory effort, starting without a preceding, inspiration, or reciprocal inhibition of occasional spontaneous inspiration. The retro-trapezoid nucleus/parafacial respiratory group neurones described as the distinct generator for active E in rats, are activated also during the ExpR in adult cats. Brainstem transection 5 mm above the obex eliminates the E generator and the ExpR, but preserves the I generator located in the pre-Bötzinger Complex, and also the AspR. This suggests the existence of a distinct I generator in cats as well as rats, and its contribution to the generation of the AspR. Persistence of the AspR in adult cats during asphyxic gasping, their similar character and the strong activation of I neurones at many places in the medulla and pons, suggest a common brainstem neuronal circuit contributing to generation of both the gasping and the gasp-like AspR. That the AspR and ExpR have distinct multilevel brainstem control mechanisms supports the dual theory of control and provides unique models for testing respiratory rhythm and pattern generation. The AspR may be compared with the powerful "auto-resuscitation effects of asphyxic gasping"; the ExpR may underly the effectiveness of the laryngeal chemoreflexes in prevention of lung diseases.

Convergence of nasal and tracheal neural pathways in modulating the cough response in guinea pigs.

In the present study we investigated the possibility of central convergence of neural pathways coming from distant anatomical regions in modulating the cough response. We addressed this issue by inducing cough from the tracheo-bronchial region on the background of capsaicin-stimulated and mesocain-blocked nasal mucosa in 14 anesthetized guinea pigs. The control group consisted of 6 guinea pigs in which the active agents, capsaicin and mesocain, were substituted for by inert physiological saline. All animals were tracheostomized, and the larynx was disconnected from the proximal part of the trachea with preserved innervations, and all were subjected to the same protocol. Cough, induced by mechanical irritation of the tracheo-bronchial mucosa, was elicited three times: in the control condition, after intranasal capsaicin challenge, and after another capsaicin challenge preceded by intranasal instillation of a local anesthetic, mesocain. The main finding of the study was that the number of cough efforts per bout, assessed from positive deflections on the intrapleural pressure recordings, was significantly enhanced by intranasal capsaicin challenge and this effect was reversed by intranasal pretreatment with the anesthetic mesocain [2.1 +/-0.2 (control) vs. 3.5 +/-0.4 (capsaicin) vs. 2.2 +/-0.2 (capsaicin after mesocain) (P<0.01)], with no appreciable changes in the magnitude of cough efforts. The cough response in the control group remained unchanged. We conclude that tracheo-bronchial cough may be modified by neural sensory input to the brain coming from nasal mucosa. Therefore, cough reflex is subject to central convergence of peripheral neural pathways originating at distant anatomical locations.

Influence of stimulation of nasal afferents on expiration reflex evoked from vocal folds.

Cough and sneezing are upregulated during the upper airway diseases, most likely to enhance airway defense. The aim of this study was to assess the expiration reflex (ER), another expulsive defensive airway reflex, during allergic rhinitis (AR) and intranasal (i.n.) capsaicin challenge. Thirty male guinea pigs, sensitized to ovalbumin were used in the study. They were divided into 3 groups of 10 animals each: AR group (i.n. ovalbumin), capsaicin group (i.n. capsaicin 50 microM, 15 microl), and controls without any challenge. The animals were anesthetized with urethane (1.1 mg/kg) and allowed to breath spontaneously via tracheostomy. Metal canula was introduced into the right hemithorax to assess intrapleural pressure. ER was elicited by mechanical stimulation of the vocal folds using a thin nylon loop introduced upwards via tracheostomy. Maximal expiratory effort of ER (MEE) and the count of post-ER laryngeal coughs were evaluated. Mechanical stimulation of the vocal folds in controls produced isolated ER. They were followed by post-ER cough only in 11% of provocations. AR and capsaicin challenge increased MEE compared with that in controls (P<0.05). In these two groups of animals, the ER was followed by post ER-cough in 75% of provocations. The count of post-ER coughs in the group order control/AR/capsaicin was 0-2/2-4/1-3, respectively; P<0.05). The ER from the vocal folds is upregulated in a similar manner as is cough and sneeze. The central neuronal mechanisms are proposed to mediate this effect, but the spread of inflammation from upper airways to the larynx, verified histologically in the present study, may contribute as well.

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.

The effect of exercise and oxidant-antioxidant intervention on the levels of neurotrophins and free radicals in spinal cord of rats.

STUDY DESIGN: This study was designed to investigate the effects of oxidant and antioxidant treatment, as well as regular exercise, on neurotrophin levels in the spinal cord of rats. OBJECTIVES: Reactive oxygen species (ROS) play a role in neurodegenerative diseases, but ROS at moderate levels could stimulate biochemical processes through redox-sensitive transcription. METHODS: Exercised or sedentary animals were injected subcutaneously with hydrogen peroxide (H(2)O(2)), N-tert butyl-alpha-phenyl nitrone (PBN) or saline for the last 2 weeks of a 10-week experimental period to challenge redox balance. Free radical (FR) concentration was evaluated in the spinal cord by electron spin resonance, protein carbonyls, brain-derived neurotrophic factor (BDNF), glial cell line-derived neurotrophic factor (GDNF) levels and the mRNA expression of BDNF receptor and tyrosine kinase receptor B (TrKB). SETTING: Research Institute of Sport Science, Semmelweis University, Budapest, Hungary. RESULTS: Exercise or PBN decreased the concentration of FR, whereas the carbonyl content did not change. BDNF was significantly decreased in exercised sham and sedentary PBN-treated groups, and its content correlated with the level of FR. GDNF was significantly increased in sedentary H(2)O(2)-treated groups. No differences were observed in TrkB mRNA expression among groups. CONCLUSIONS: Results suggest that regular exercise alone and PBN in sedentary animals can successfully decrease FR levels in the spinal cord. Redox alteration seems to affect the levels of GDNF and BDNF, which might have clinical consequences, as neurotrophins play an important role in cellular resistance and regeneration.

Medullary raphe midline is involved in production of expulsive expirations in anesthetized rabbits.

Effects of kainic acid lesions in the medullary raphe midline on reflex expirations induced mechanically from the trachea were examined. Spontaneously breathing rabbits were anesthetized by ketamine and xylazine i.m., followed by pentobarbitone i.v. Excitatory neurotoxin kainic acid (2 mg/ml in artificial CSF, total volume of 55-100 nl) was pressure microinjected into the medullary midline, rostral to the obex (2 microinjections at 2 different depths). The lesion (mostly affected the obscurus and magnus raphe nuclei) reduced the number of reflex expirations by 80% and expiratory amplitudes of esophageal pressure, abdominal EMG moving averages, and abdominal EMG powers by 71%, 62%, and 57%, respectively (in all cases P<0.05). The duration of abdominal activity in post-lesion responses was not altered. Control microinjections of artificial CSF had no effect on the reflex responses. We conclude that in rabbits, the medullary raphe nuclei participate in the control of expiratory expulsions originating from the trachea.