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At least 127 records · Page 7Linked to original sources
PubMed2002

Activation of mu-opioid receptors in rat ventrolateral medulla selectively blocks baroreceptor reflexes while activation of delta opioid receptors blocks somato-sympathetic reflexes.

The effects of activation of mu and delta-opioid receptors in the rostral ventrolateral medulla (RVLM) on somato-sympathetic, baroreceptor and chemoreceptor reflexes, as well as respiratory rhythmicity in sympathetic nerves, were examined in urethane anaesthetized (1.1-1.2 g/kg) and artificially ventilated Sprague-Dawley rats. Microinjection of the delta-opioid receptor agonist [D-Pen(2,5)]-enkephalin (DPDPE; 8 mM, 50 nl) bilaterally into the RVLM potently inhibited the post-inspiratory-related burst discharges of lumbar sympathetic nerve activity (LSNA) but had only limited effects on splanchnic sympathetic nerve activity (SSNA) and phrenic nerve discharge. Injection of DPDPE into the RVLM strongly attenuated the somato-sympathetic reflex (approximately 50-80%) evoked in the lumbar sympathetic nerve and splanchnic sympathetic nerve by tibial nerve stimulation but had no effect on baroreceptor reflexes and chemoreceptor reflexes evoked by aortic nerve stimulation and brief hypoxia, respectively. Injection of the mu-opioid receptor agonist, [D-Ala(2),N-Me-Phe(4),Gly-ol(5)]-enkephalin (DAMGO; 4 mM, 50 nl), also elicited a greater inhibition of LSNA than SSNA accompanied by an abolition of phrenic nerve discharge. Injection of DAMGO inhibited the baroreceptor reflex without significant effect on either the somato-sympathetic or the chemoreceptor reflexes. We propose that opioid peptides diminish specific excitatory and inhibitory inputs to the presympathetic neurons in RVLM via distinct presynaptic receptor subclasses.

Action Potentials↗
PubMed1988

Stabilizing gaze reflexes in the pigeon (Columba livia). II. Vestibulo-ocular (VOR) and vestibulo-collic (closed-loop VCR) reflexes.

The vestibulo-ocular reflex (VOR) and the closed-loop vestibulo-collic reflex (CL-VCR) were investigated in the pigeon. The animals, placed either in the fixed-head condition (VOR) or in the free-head condition (CL-VCR) were rotated in darkness (vestibular responses) or in the presence of visual surroundings (visuo-vestibular responses). The linear range of the reflexes were determined both in the frequency and in the velocity domains. Results show that: 1. Pigeons develop a strong VOR, which presents the same asymmetry observed with the OKN, the gain being higher when the slow-phase occurs in the T-N direction. This asymmetry persists in the light (VOR + OKN). In the free-head condition, both the eye and the head display a synchronized nystagmus whose effects are additive. The head reflex (CL-VCR) contributes about 80% of the gaze stabilization. 2. In the medium-low frequency range, the head response (CL-VCR) has a lower gain than the VOR (head-fixed), but the gain of both reflexes increases with frequency, up to about 1 at 0.6-1 Hz. The gaze response (eye + head) presents an optimal gain above 0.06 Hz. The phase lead is higher for the VOR than for the CL-VCR (40 degrees and 32 degrees respectively at 0.03 Hz), but both phases also become nul around 1 Hz. The time constants are 6.5 s for the VOR, 8.5 s for the CL-VCR and 9.6 s for the gaze response (VOR + CL-VCR). 3. While the VOR gain shows a saturation at peak stimulation velocities (PV) higher than 20 degrees/s (at 0.3 Hz), the CL-VCR gain is linear at least up to 60 degrees/s (the highest PV used). However, the phase lead declines when the PV is greater than 20 degrees/s, both for the VOR and the CL-VCR. 4. When the vestibular stimulation is delivered in the light (visuo-vestibular stimulation), there is no phase shift. The VOR gain (fixed-head) is optimal and linear over the entire frequency range, but it saturates for PV higher than 40 degrees/s. In the free-head condition, while the gaze gain is linear and close to 1 in both the frequency and the velocity domains, the head response gain (CL-VCR) remains lower especially in the low frequency and in the low velocity ranges.

Animals↗
PubMed1996

Reflex sympathetic dystrophy: skin blood flow, sympathetic vasoconstrictor reflexes and pain before and after surgical sympathectomy.

To examine the pathophysiological mechanisms of vascular disturbances and to assess the role of the sympathetic nervous system, 12 patients with reflex sympathetic dystrophy (RSD) of the hand were studied using laser Doppler flowmetry. Cutaneous blood flow, skin resistance and skin temperature were measured at the affected and contralateral hands. Sympathetic vasoconstrictor reflexes were induced bilaterally by deep inspiration. Four patients were treated with unilateral surgical sympathectomy and pain and vascular changes were documented in follow-up investigations. (1) After acclimatization in cold environment (< or = 18 degrees C) blood flow and skin temperature were considerably lower on the affected side in 10 patients. No additional vasoconstrictor reflexes could be elicited. (2) After acclimatization in warm environment (22-24 degrees C) blood flow and skin temperature demonstrated no side differences in all cases. Vasoconstrictor responses were the same on both sides. (3) After sympathectomy vasoconstrictor reflexes were absent. Skin resistance was considerably higher on the affected side. In the first 4 weeks the affected hand was warmer and blood flow was higher compared with the healthy side. Thereafter, skin temperature and perfusion slowly decreased and the affected hand turned from warm to cold. Very regular high amplitude vasomotion waves occurred unilaterally. There were no signs of reinnervation. Two patients had long-term pain relief. We conclude as follows. (1) Side differences in skin temperature and blood flow are no static descriptors in RSD. They are dynamic values depending critically on environmental temperature. Therefore, they have to be interpreted with care when defining reliable diagnostic criteria. (2) Vascular disturbances in RSD are not due to constant overactivity of sympathetic vasoconstrictor neurons. Changes in vascular sensitivity to cold temperature and circulating catecholamines may be responsible for vascular abnormalities. Alternatively, RSD may be associated with an abnormal (side different) reflex pattern of sympathetic vasoconstrictor neurons due to thermoregulatory and emotional stimuli generated in the central nervous system. (3) After sympathectomy, denervation supersensitivity of blood vessels and intense vasomotion may be associated with recurrence of pain in some patients.

Adult↗
PubMedDate not supplied

[Soleus muscle reflexes evoked by stimulation of the posterior tibial nerve compared to tendon reflexes in man (author's transl)].

The characteristics of the reflex response evoked in the soleus muscle after stimulation of the posterior tibial nerve at the ankle were contrasted with the achilleus tendon reflex in 14 healthy volunteers and in a group of selected neurological patients. The following features were examined: conditions of stimulation including stimulation frequency; appearance of reflex activity in muscles other than soleus, effect of the vibratory stimulation, interactions with voluntary contraction. Moreover, a reflex response is described in the soleus following stimulation of the sural nerve. The results have shown a marked jitter in latencies of the responses, a pattern of coactivation of antagonistic muscles, a clear increase of amplitude under vibration or voluntary contraction, normal responses both in spasticity and in S1 radiculopathy with achilleus areflexia. All these data differ from those observed with the tendon jerk of the same amplitude and differentiate the two responses. It is concluded that the reflex evoked by stimulation of the tibial nerve at the ankle is a polysynaptic response of cutaneous origin.

Achilles Tendon↗
PubMed2003

Role of positive anorectal feedback in rectal evacuation: the concept of a second defecation reflex: the anorectal reflex.

BACKGROUND/OBJECTIVE: The present study investigated the hypothesis that rectal contraction is maintained by positive anorectal feedback elicited by continuous passage of stools through the rectal neck (anal canal), and that cessation of stool passage aborts rectal contraction. METHODS: Anal and rectal pressures were measured in 18 healthy volunteers (mean age = 38.6 years; 10 men, 8 women) during evacuation of saline infused into the rectum. Residual fluid volume was calculated. The test was repeated after separate application of lidocaine or bland gel to the rectal neck. RESULTS: On evacuation, fluid emanated from the rectal neck in continuous flow with no, or mild, straining. No residual saline was collected from 16 of 18 participants. After anal anesthetization, evacuation occurred in gushes induced with excessive straining; residual fluid was huge. Repetition of the test 2 hours after anesthetization produced the same results as before anesthetization. Bland gel applied to the rectal neck yielded results similar to those before gel application. CONCLUSION: Rectal contraction at defecation is suggested to be maintained by positive anorectal feedback evoked by continuous passage of stool through the rectal neck. This feedback appears to be affected through an anorectal excitatory reflex (ARR), which produces rectal contraction upon stimulation of anal stretch receptors. Abortion of this reflex by anal anesthetization seems to result in failure of the rectum to contract and in excessive straining to achieve rectal evacuation. ARR thus is suggested to be a second defecation reflex necessary to continue defecation, whereas the rectoanal inhibitory reflex is the primary reflex. The role of the ARR in pathogenesis of constipation and its utility in spinal cord injury need to be investigated.

Adult↗
PubMed1990

H-reflex recovery curve and reciprocal inhibition of H-reflex in different kinds of dystonia.

We studied the H-reflex recovery curve and reciprocal inhibition of the H-reflex bilaterally in the upper limb of 5 patients with generalized dystonia, 5 patients with blepharospasm, 10 patients with spasmodic torticollis, and 14 patients with writer's cramp. We compared the results with those obtained from a group of healthy volunteers. The recovery curve of the H-reflex was normal in patients with writer's cramp or blepharospasm, but showed an increase of the physiologic recovery at a 200 msec delay in patients with spasmodic torticollis or generalized dystonia. Reciprocal inhibition of the H-reflex showed a decrease in the amount of inhibition in all the patient groups and a facilitation of the H-reflex during the 3rd period of inhibition in the patients with spasmodic torticollis or generalized dystonia.

Adult↗
PubMed2001

Effect of pelvic floor muscle contraction on vesical and rectal function with identification of puborectalis-rectovesical inhibitory reflex and levator-rectovesical excitatory reflex.

The effects of pelvic floor muscle contraction on rectal and vesical function were studied in 19 healthy volunteers with the aim of shedding light on some of the hitherto vague aspects of the mechanisms involved in micturition and defecation and their disorders. Rectal and vesical pressures were recorded during puborectalis (PR) and levator ani (LA) muscle stimulation with the rectum or urinary bladder empty and full. Muscle stimulation was effected by needle EMG electrode. The pressure responses to stimulation of the PR and LA muscles were also recorded with these muscles and the rectum and urinary bladder individually anesthetized in 12 of the 19 subjects. The test was repeated using saline instead of xylocaine. PR and LA muscle stimulation produced no pressure response in the empty rectum or bladder. Upon rectal balloon distension with a mean of 156.6+/-34.2 ml of carbon dioxide the mean rectal pressure was 64.6+/-18.7 cm H2O, the subject felt the urge to evacuate and the balloon was expelled to the exterior. On PR muscle stimulation at rectal distension with the above volume, the subject did not feel the urge to evacuate, the rectal pressure was 8.2+/-1.6 cm H2O and the balloon was not expelled. Upon LA stimulation at the same volume, the urge persisted, the rectal pressure was higher and the balloon was expelled. Vesical filling with a mean of 378.2+/-23.6 ml of saline initiated the urge to urinate and elevated the vesical pressure. PR muscle stimulation at this volume aborted the urge and pressure elevation, while LA stimulation caused more elevation of the vesical pressure and spontaneous micturition. Bladder filling with a mean of 423.6+/-38.2 ml produced high vesical pressure and spontaneous urination, both of which were prevented by PR muscle stimulation but not by LA muscle stimulation. Stimulation of the PR and LA muscles during individual anesthetization of the rectum, bladder or PR and LA muscles resulted in no significant rectal or vesical pressure changes. Repetition of the test using saline instead of xylocaine resulted in rectal and vesical pressure responses similar to those without the use of saline. In conclusion, the decline in rectal and vesical responses upon PR muscle contraction indicates a reflex relationship which we term 'puborectalis rectovesical inhibitory reflex'. This reflex is suggested to abort the urge to defecate or urinate. In contrast, LA muscle contraction produced rectal and vesical pressure elevation which is suggested to be mediated through the 'levator rectovesical excitatory reflex'. 'This reflex is probably evoked to promote rectal and vesical evacuation.

Adolescent↗
PubMed1995

Vagino-levator reflex: description of a reflex and its role in sexual performance.

A new reflex, termed the 'vagino-levator reflex', was studied in 17 healthy women (mean age 36.6 years). The vagina was distended with up to 300 ml air in a condom tied to a catheter, and the levator ani response was determined by means of needle electrode introduced into the muscle. The test was repeated after anesthetizing the vagina and the levator muscle, respectively. The levator EMG activity rose when the vagina was distended; the amplitude and duration of activity increased in parallel with vaginal distension. The levator response did not occur after successive repetition of vaginal distension due probably to levator muscle fatigue; nor did it occur after anesthetizing the vagina or the levator muscle. The mean latency of the reflex was 39.5 ms. The vagino-levator reflex seems to play a role in the sexual act. Levator contraction upon penile thrusting leads to genital responses that could facilitate sexual performance. These responses comprise widening of the vaginal introitus, vaginal elongation and ballooning of the upper vagina as well as uterine elevation. Vagino-levator reflex dysfunction may result in disorders of sexual act.

Adult↗
PubMed1987

Difference in electromyographic response of finger flexion muscles between tonic vibration reflex and finger flexion reflex induced by finger tip vibration.

Vibratory stimulus applied to the skin of the finger tip induced flexion reflex in that finger. By using the cross-correlation function, characteristics of this reflex were compared to those of tonic vibration reflex (TVR). In the cross-correlogram between unitary electromyogram (EMG) activity in the muscle flexor digitorum superficialis and vibratory stimulus with random frequency, one mode was seen in TVR, and two modes in finger flexion reflex. The secondary mode was significantly wider than the primary mode. Thus it may originate from skin mechanoreceptors and manifest via a reflex center involving a long loop.

Adult↗
PubMed1993

Flexion reflexes following anterolateral cordotomy in man: dissociation between pain sensation and nociceptive reflex RIII.

Nociceptive flexion reflexes (RIII response) of the lower limbs were recorded after unilateral cervico-thoracic anterolateral cordotomy (ALC) in 7 patients. Pre-operative recordings were also obtained in 1 patient and follow-up observations in 3 patients. Flexion reflexes ipsilateral to cordotomy remained normal after surgery. Conversely, responses contralateral to the cordotomy exhibited two consistent postoperative changes: first, the RIII reflex was always dissociated from subjective pain, i.e., it appeared in the absence of any pain sensation, and, second, the RIII was depressed in the limb contralateral to ALC in 5 of 7 patients. RIII attenuation ranged from slight reduction to total abolition, and proved to be reversible in 2 of 3 patients tested during the follow-up. The reappearance of withdrawal reflexes was never accompanied by a recovery of pain sensation in the stimulated limb. We conclude that the dissociation between flexion reflexes and pain sensation, which was evidenced even in case of depressed RIII responses, should be attributable to the surgical lesion of spinothalamic fibers. Dissociation between RIII and subjective pain is a landmark indicating a lesion of the spinothalamic fibers, and may be used for the clinical assessment of spinothalamic dysfunction. Conversely, RIII depression after ALC does not depend upon the surgical lesion to the spinothalamic axons, but may be secondary to interruption of ascending spinoreticular fibers in the anterolateral quadrant, and/or of descending excitatory axons in the ventral cord.

Adult↗
PubMed2000

Contribution of TTX-resistant C-fibres and Adelta-fibres to nociceptive flexor-reflex and non-flexor-reflex pathways in cats.

The contribution of Adelta-fibres and C-fibres activated by noxious heat stimulation of the central pad of the foot to nociceptive spinal flexor reflex pathways (FRA-type) and to nociceptive excitatory reflex pathways to foot extensors (non-FRA type) was investigated in high spinal cats. A-fibres were completely blocked by tetrodotoxin (TTX), leaving C-fibre conduction intact. Thus, effects persisting after TTX were attributed to nociceptive C-fibres while the contribution of nociceptive Adelta-fibres was defined by the difference between those effects and the control effects before TTX. The initial action of noxious stimulation on both types of reflex action was mediated predominantly by Adelta-fibres, while the later action was mainly mediated by C-fibres. In two (out of seven) experiments Adelta-fibres exerted a significant inhibitory influence on the C-fibre action in FRA pathways, but such an inhibitory interaction between the two fibre groups was absent in the non-FRA reflex pathways. The technique of TTX application at the peripheral nerve proved to be a reliable method for a long-lasting selective investigation of C-fibre effects. The results revealed that both Adelta- and C-fibres contributed to nociceptive FRA and non-FRA reflex pathways.

Animals↗
PubMed1983

The Bezold-Jarisch reflex revisited: clinical implications of inhibitory reflexes originating in the heart.

The concept of depressor reflexes originating in the heart was introduced by von Bezold in 1867 and was later revived by Jarisch. The Bezold-Jarisch reflex originates in cardiac sensory receptors with nonmyelinated vagal afferent pathways. The left ventricle, particularly the inferoposterior wall, is a principal location for these sensory receptors. Stimulation of these inhibitory cardiac receptors by stretch, chemical substances or drugs increases parasympathetic activity and inhibits sympathetic activity. These effects promote reflex bradycardia, vasodilation and hypotension (Bezold-Jarisch reflex) and also modulate renin release and vasopressin secretion. Conversely, decreases in the activity of these inhibitory sensory receptors reflexly increase sympathetic activity, vascular resistance, plasma renin activity and vasopressin. Long regarded as pharmacologic curiosities, it is now clear that reflexes originating in these inhibitory cardiac sensory receptors are important to the pathophysiology of many cardiovascular disorders. This paper reviews the role of inhibitory cardiac sensory receptors in several clinical states including 1) bradycardia, hypotension and gastrointestinal disorders with inferoposterior myocardial ischemia and infarction, 2) bradycardia and hypotension during coronary arteriography, 3) exertional syncope in aortic stenosis, 4) vasovagal syncope, 5) neurohumoral excitation in chronic heart failure, and 6) the therapeutic effects of digitalis.

Animals↗
PubMed2003

Study of the role of the second defecation reflex: anorectal excitatory reflex in the pathogenesis of constipation.

BACKGROUND: Previous studies have shown that anal distension caused rectal contraction, an action mediated through the anorectal excitatory reflex. Anal anesthetization aborted rectal contraction and rectal evacuation was induced by excessive straining. We investigated the hypothesis that inhibition or absence of the anorectal excitatory reflex could lead to constipation. METHODS: We studied 18 patients (mean age +/- SD: 40.6 +/- 5.8 years, 14 women) with rectal inertia, 14 (41.7 +/- 6.6 years, 12 women) with puborectalis paradoxical syndrome, and 10 healthy volunteers (37.9 +/- 4.8 years, 8 women). The rectum was filled with normal saline until urge and then evacuated; residual fluid was calculated. The anal and rectal pressure response to anal balloon distension in increments of 2 mL of saline was recorded by a two-channel microtip catheter. RESULTS: In the healthy volunteers, saline was evacuated as a continuous stream without straining except occasionally at the start of evacuation; no residual fluid was encountered. Anal balloon distension effected notable rectal pressure increase. In rectal inertia patients, evacuation occurred in small fluid gushes produced with excessive straining; residual fluid of large volume was collected. Anal balloon distension up to 10 mL produced no notable rectal pressure changes. The patients with PPS failed to evacuate more than a few mL of fluid despite excessive straining; the volume of residual fluid was considerable. Anal balloon distension caused a notable rectal pressure rise. The results were reproducible. CONCLUSIONS: These results suggest that the defecation reflexes (rectoanal and anorectal) are absent in rectal inertia patients and this presumably denotes a neurogenic disorder. The anorectal reflex is active in puborectalis paradoxical syndrome, but the rectoanal reflex is not, indicating a possible myogenic defect in the puborectalis muscle.

Adult↗
PubMed2001

Rectal inhibition by inferior rectal nerve stimulation in dogs: recognition of a new reflex--the 'voluntary anorectal inhibition reflex'.

OBJECTIVE: The effect of inferior rectal nerve (IRN) stimulation on the rectum was studied, postulating that nerve stimulation might inhibit rectal contractility and could thus be used in the management of defecation disorders. METHOD: The IRN was exposed through a para-anal incision in 12 dogs (18.2 +/- 3.3 SD kg, seven male, five female) and a cuff-type electrode was applied to the nerve. A balloon introduced into the rectum was filled with saline in increments of 5 ml. The rectal and rectal neck (anal canal) pressures, and the electromyographic (EMG) activity of the external anal sphincter (EAS) and Internal anal sphincter (IAS) were recorded until the balloon was expelled to the exterior. The test was repeated until the expulsion volume was reached, and the IRN was stimulated (pulse width 200 mu/s, charge density 2 to 6 microCi/cm2 per phase). The test was performed again following individual anaesthetization of the EAS and the IAS. RESULTS: At a mean rectal distending volume of 38.3 +/- 2.3 ml, the rectal pressure increased (P < 0.01), rectal neck pressure declined (P < 0.01), the EAS and IAS EMGs disappeared, and the balloon was expelled. IRN stimulation at a distending volume of 38.3 +/- 2.3 ml increased the EMG activity of the EAS, whereas the rectal pressure and IAS EMG did not change (P > 0.05) and the balloon was not expelled. With IRN stimulation at the distending volume of 38.3 +/- 2.3 ml while the EAS was anaesthetized, the rectal pressure increased (P < 0.01), rectal neck pressure diminished, IAS EMG activity disappeared, and the balloon was expelled. Upon repetition of IRN stimulation during anaesthetization of the IAS, the rectal pressure remained high and the balloon was not expelled. CONCLUSION: It is suggested that the EAS produces continence by a twofold action. The EAS prevents IAS relaxation on rectal contraction, with a resulting rectal relaxation. A reflex relationship is postulated to exist between failure of the IAS to relax and rectal relaxation. We call this reflex relationship 'voluntary anorectal inhibition reflex'. Secondly, the EAS mechanically compresses the rectal neck. It seems that contraction of the EAS, which is a striated muscle, mechanically occludes the rectal neck for a few seconds--enough for the rectum to relax in a reflex manner as an effect of the voluntary anorectal inhibition reflex.

Animals↗
PubMed2002

Development of a quantitative reflex hammer for measurement of tendon stretch reflex.

Quantification of tendon stretch reflex requires precise measurement of the tapping force of a reflex hammer. A quantitative reflex (QR) hammer consisting of two cut rubber pieces from a generic rubber reflex hammer and a uniaxial force transducer was constructed. Finite element stress analyses were conducted to estimate the natural frequency characteristics of the hammer and to find the stress distributions during the impact. Pendulum impact testing was conducted at four different heights to assess the calibration linearity and repeatability of the measurement. The QR hammer had a fundamental natural frequency of 515 Hz and showed minimal displacement and stress at the tip from the finite element simulation of the impact. The QR hammer also provided reliable and repeatable measurements as demonstrated with high coefficients of determination, exceeding 0.994 and small coefficients of variations, less than 4%. The calibration linearity was 0.64% compared with the reference force platform measurement. The QR hammer demonstrated sufficient accuracy and reliability for precise clinical assessment of tendon stretch reflexes.

Calibration↗
PubMed1977

Effects of postural changes of the upper limb on reflex transmission in the lower limb. Cervicolumbar reflex interactions in man.

The influence of passive changes in upper limb position on the excitability of three myotatic arc reflexes (soleus, quadriceps, and biceps femoris) of the lower limb has been explored on 42 volunteers. The results indicate that the excitability of the three myotatic arcs can be influenced at a distance by postural modifications of the upper limb. When the ipsilateral upper limb is forwards or the contralateral backwards, a facilitation of both soleus and quadriceps tendon reflexes is observed while the biceps femoris reflexes are reduced. This pattern of facilitation and inhibition is reversed when the ipsilateral upper limb is backwards or the contralateral forwards. The facilitations as well as inhibitions of proximal myotatic arc reflexes are quantitatively more marked than that of the soleus reflex. Facilitation and inhibition are not linearly related to the angle of the arm with the trunk. Effects begin at a considerable angle, become maximal at 45 degrees, and progressively disappear for greater values. It is suggested that the distinct pattern of facilitation and inhibition which is exerted in reciprocal fashion on extensor and flexor motor nuclei might depend on the long propriospinal neurones connecting cervical and lumbar enlargements.

Achilles Tendon↗
PubMed1994

Reflex effects of lung inflation on tracheomotor tone observed during apnea produced by the Hering-Breuer reflex.

Reflex effects of static pressure lung inflation (SLI) on tracheomotor tone (TT) were studied during apnea produced by the Hering-Breuer expiratory-facilitatory reflex. Anesthetized dogs were placed on cardiopulmonary bypass, and diaphragm electromyogram was used as an indicator of central nervous system inspiratory output. Tracheomotor tone (TT) was reflexly produced by chemoreceptor stimulation. The volume and frequency of the ventilator [phasic lung inflation (PLI)] were adjusted to produce nearly a maximum reflex decrease in TT. The increase in TT observed while PLI was withheld (0 mmHg tracheal pressure) for 1-2 min was used as the control response. SLIs were interspersed among sets of PLIs. Although SLI produced apnea, TT returned toward the control TT recorded during 0 mmHg tracheal pressure. TT observed during apnea was reflexly sensitive to further increases in SLI and to changes in chemoreceptor stimulation, which also affected the time course of the tracheomotor responses. These results suggest that the reflex decrease in TT produced by SLI and the Hering-Breuer expiratory-facilitatory reflex are mediated by different central mechanisms but may be from the same or different pulmonary receptors.

Air Pressure↗
PubMed1978

Studies on the mechanism of reflex vasodilatation. The cholinergic component in the baroreceptorial reflex in the dog.

This study was designed to investigate whether the cholinergic system is involved in the genesis of the reflex vasodilatation which follows the systemic hypertension induced by fast intravenous injection of norepinephrine in the dog. Accordingly, in 7 dogs the gracilis muscle was isolated and perfused and the reflex evoked. The analysis of the integrated areas of vasodilatation after atropine pretreatment showed a significant decrease of the reflex response in the perfused circulation. In fact, the mean value of the integrated areas of vasodilatation which was 66 +/- 8 mm Hg/min in the control condition, was reduced to 45 +/- 4 mm Hg/min after administration of atropine in the gracilis artery; meanwhile the integrated areas of systemic hypertension did not show any change. Phentolamine intra-arterial administration completely abolished the reflex. These results suggest the existence of a cholinergic component in the reflex vasodilatation induced by transitory baroreceptorial stimulation.

Animals↗