Influence of ventrolateral surface of medulla on reflex tracheal constriction

To assess the role of structures located superficially near the ventrolateral surface of the medulla on the reflex constriction of tracheal smooth muscle that occurs when airway and pulmonary receptors are stimulated mechanically or chemically, experiments were conducted in alpha-chloralose-anesthetized, paralyzed, and artificially ventilated cats. Pressure changes within a bypassed segment of the trachea were used as an index of alterations smooth muscle tone. The effects of focal cooling of the intermediate areas or topically applied lidocaine on the ventral surface of the medulla on the response of the trachea to mechanical and chemical stimulation of airway receptors were examined. Atropine abolished tracheal constriction induced by mechanical stimulation of the carina or aerosolized histamine, showing that the responses were mediated over vagal pathways. Moderate cooling of the intermediate area (20 degrees C) or local application of lidocaine significantly decreased the tracheal constrictive response to mechanical activation of airway receptors. Furthermore, when the trachea was constricted by histamine, cooling of the intermediate area significantly diminished the increased tracheal tone, whereas rewarming restored tracheal tone to the previous level. These findings suggest that under the conditions of the experiments the ventral surface of the medulla plays an important role in constriction of the trachea by inputs from intrapulmonary receptors and in the modulation of parasympathetic outflow to airway smooth muscle.

Download Full-text

Cholinergic neurotransmission in human corpus cavernosum. I. Responses of isolated tissue

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1988.254.3.h459 ◽

1988 ◽

Vol 254 (3) ◽

pp. H459-H467 ◽

Cited By ~ 5

Author(s):

I. Saenz de Tejada ◽

R. Blanco ◽

I. Goldstein ◽

K. Azadzoi ◽

A. de las Morenas ◽

...

Keyword(s):

Smooth Muscle ◽

Electrical Stimulation ◽

Muscle Tone ◽

Corpus Cavernosum ◽

Cholinergic Nerves ◽

Smooth Muscle Tone ◽

Cholinergic Neurotransmission ◽

Stimulation Of

To investigate the role of cholinergic neurotransmission in erection, human penile corpus cavernosum tissue was studied. Electrical stimulation of strips of corpus cavernosum suspended in an organ chamber induced contractions and relaxations that were blocked by tetrodotoxin. The contractions also were blocked by bretylium and prazosin. Norepinephrine and phenylephrine contracted the isolated strips and this response was prevented by prazosin. Electrical stimulation-induced relaxations were enhanced by bretylium and physostigmine and partially blocked by atropine. The effect of atropine, but not that of physostigmine, was prevented by bretylium. Corporal strips contracted with norepinephrine relaxed to acetylcholine; this effect was blocked by atropine and enhanced by physostigmine. Strips lacking endothelium contracted normally with norepinephrine, but the relaxation caused by acetylcholine was virtually abolished. Thus endothelium lining the lacunar spaces within human corpus cavernosum is required for the relaxation caused by exogenous acetylcholine. There may be three neurotransmitter effector systems that control corpus cavernosum smooth muscle tone: adrenergic (excitatory), cholinergic (inhibitory), and nonadrenergic noncholinergic (inhibitory). Cholinergic nerves do not dilate or constrict directly the smooth muscle but may modulate other neuroeffector systems and/or the endothelium.

Download Full-text

Benzodiazepines acting on ventral surface of medulla cause airway dilation

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1989.257.4.r810 ◽

1989 ◽

Vol 257 (4) ◽

pp. R810-R815 ◽

Cited By ~ 4

Author(s):

M. A. Haxhiu ◽

E. van Lunteren ◽

N. S. Cherniack ◽

E. C. Deal

Keyword(s):

Smooth Muscle ◽

Muscle Tone ◽

Muscle Tension ◽

Ventral Surface ◽

Gamma Aminobutyric Acid ◽

Tracheal Pressure ◽

Parasympathetic Neurons ◽

Lung Deflation ◽

Airway Tone ◽

Alpha Chloralose

The benzodiazepines that have anxiolytic, anticonvulsant, muscle-relaxant, and sedative-hypnotic properties affect respiration possibly by acting on gamma-aminobutyric acid (GABA)ergic receptors. This study investigated the effects of benzodiazepines diazepam and midazolam) applied topically to or microinjected just beneath the ventrolateral medullary surface (VMS) on airway tone in alpha-chloralose-anesthetized, paralyzed, and artificially ventilated cats. Trachealis smooth muscle tension was assessed by measuring the changes in pressure in a balloon placed in a bypassed rostral segment of the trachea. In 21 cats ventilated with 7% CO2 in O2, surface application of benzodiazepines caused a significant decrease in tracheal tone. Similar to topical application, microinjection of midazolam (1 microgram) in the ventral medulla (0.1-0.2 mm from the surface) in six cats decreased tracheal pressure by 13.2 +/- 2.1 cmH2O (P less than 0.01). In addition, application of benzodiazepines on the VMS in animals ventilated with 12% O2 in N2 (n = 5) decreased tracheal pressure from 15.9 +/- 2.2 to 5.2 +/- 2.7 cmH2O (P less than 0.05). Furthermore, in all cats studied (n = 6), the magnitude of lung deflation-induced tracheal contraction was reduced after application of benzodiazepines on the ventral surface of the medulla (from 11.4 +/- 1.6 to 2.2 +/- 0.9 cmH2O; P less than 0.01). The effects of benzodiazepines on tracheal tone were reversed and blocked by application of Ro 15-1788, a specific benzodiazepines antagonist. However, when parasympathetic activity was abolished by atropine and tracheal tone was restored with 5-hydroxytryptamine, benzodiazepines applied on the VMS had no effect on tracheal pressure. These results suggest that benzodiazepines acting centrally, on structures located near the VMS, can cause a decrease in airway smooth muscle tone by diminishing the activity of parasympathetic neurons which project to the airways.

Download Full-text

Role of cyclic GMP in atrial natriuretic factor stimulation of Na+,K+,Cl- cotransport in vascular smooth muscle cells.

Journal of Biological Chemistry ◽

10.1016/s0021-9258(18)66734-1 ◽

1986 ◽

Vol 261 (33) ◽

pp. 15461-15466

Author(s):

M E O'Donnell ◽

N E Owen

Keyword(s):

Smooth Muscle ◽

Vascular Smooth Muscle ◽

Smooth Muscle Cells ◽

Vascular Smooth Muscle Cells ◽

Cyclic Gmp ◽

Atrial Natriuretic Factor ◽

Muscle Cells ◽

Natriuretic Factor ◽

Stimulation Of

Download Full-text

Role of paraventricular and supraoptic nuclei in central cardiovascular regulation in the cat

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1980.239.1.r137 ◽

1980 ◽

Vol 239 (1) ◽

pp. R137-R142 ◽

Cited By ~ 12

Author(s):

J. Ciriello ◽

F. R. Calaresu

Keyword(s):

Heart Rate ◽

Cardiovascular Responses ◽

Inhibitory Influence ◽

Sympathetic Nervous Systems ◽

Aortic Depressor Nerve ◽

Bilateral Lesions ◽

Alpha Chloralose ◽

Supraoptic Nuclei ◽

Stimulation Of

To investigate the role of the paraventricular (PAH) and supraoptic (SON) nuclei in regulation of the cardiovascular system experiments were done in 26 cats anesthetized with alpha-chloralose, paralyzed, and artificially ventilated. Electrical stimulation of histologically verified sites in the region of the PAH and SON elicited increases in arterial pressure in bilaterally vagotomized animals and increases in heart rate both in spinal (C2) animals and in animals bilaterally vagotomized, In addition, stimulation of either the PAH or SON inhibited the reflex vagal bradycardia elicited by stimulation of the carotid sinus nerve (CSN) and bilateral lesions of these areas increased the magnitude of the response. On the other hand, stimulation and lesions of these hypothalamic regions did not alter the magnitude of the cardiovascular responses to stimulation of the aortic depressor nerve. These results demonstrate that stimulation of the PAH and SON elicit cardiovascular responses due to reciprocal changes in activity of the parasympathetic and sympathetic nervous systems and that these structures maintain a tonic inhibitory influence on the heart rate component of the CSN reflex.

Download Full-text

Functional anatomy of the vagal innervation of the cervical trachea of the dog

Journal of Applied Physiology ◽

10.1152/jappl.2000.89.1.139 ◽

2000 ◽

Vol 89 (1) ◽

pp. 139-142 ◽

Cited By ~ 7

Author(s):

Robert L. Coon ◽

Patrick J. Mueller ◽

Philip S. Clifford

Keyword(s):

Smooth Muscle ◽

Vagus Nerve ◽

Neural Control ◽

Muscle Tone ◽

Cuff Pressure ◽

Vagal Innervation ◽

Cervical Trachea ◽

The Right ◽

Left Vagus ◽

Stimulation Of

The canine cervical trachea has been used for numerous studies regarding the neural control of tracheal smooth muscle. The purpose of the present study was to determine whether there is lateral dominance by either the left or right vagal innervation of the canine cervical trachea. In anesthetized dogs, pressure in the cuff of the endotracheal tube was used as an index of smooth muscle tone in the trachea. After establishment of tracheal tone, as indicated by increased cuff pressure, either the right or left vagus nerve was sectioned followed by section of the contralateral vagus. Sectioning the right vagus first resulted in total loss of tone in the cervical trachea, whereas sectioning the left vagus first produced either a partial or no decrease in tracheal tone. After bilateral section of the vagi, cuff pressure was recorded during electrical stimulation of the rostral end of the right or left vagus. At the maximum current strength used, stimulation of the left vagus produced tracheal constriction that averaged 28.5% of the response to stimulation of the right vagus (9.0 ± 1.8 and 31.6 ± 2.5 mmHg, respectively). In conclusion, the musculature of cervical trachea in the dog appears to be predominantly controlled by vagal efferents in the right vagus nerve.

Download Full-text

Role of the Sympathetic Nervous System and Endogenous Catecholamines in the Regulation of Airways Smooth Muscle Tone

Airways Smooth Muscle ◽

10.1007/978-3-0348-7558-5_2 ◽

1994 ◽

pp. 29-41 ◽

Cited By ~ 4

Author(s):

Philip W. Ind

Keyword(s):

Nervous System ◽

Smooth Muscle ◽

Sympathetic Nervous System ◽

Muscle Tone ◽

Smooth Muscle Tone ◽

Airways Smooth Muscle ◽

Endogenous Catecholamines ◽

Sympathetic Nervous

Download Full-text

Influence of the ventral surface of the medulla on tracheal responses to CO2

Journal of Applied Physiology ◽

10.1152/jappl.1986.61.3.1091 ◽

1986 ◽

Vol 61 (3) ◽

pp. 1091-1097 ◽

Cited By ~ 19

Author(s):

E. C. Deal ◽

M. A. Haxhiu ◽

M. P. Norcia ◽

J. Mitra ◽

N. S. Cherniack

Keyword(s):

Motor Activity ◽

Phrenic Nerve ◽

Ventral Surface ◽

Intermediate Area ◽

Tracheal Pressure ◽

Cervical Trachea ◽

Airway Responses ◽

Airway Tone ◽

Pressure Changes ◽

Nerve Discharge

These studies investigated the role of the intermediate area of the ventral surface of the medulla (VMS) in the tracheal constriction produced by hypercapnia. Experiments were performed in chloralose-anesthetized, paralyzed, and artificially ventilated cats. Airway responses were assessed from pressure changes in a bypassed segment of the rostral cervical trachea. Hyperoxic hypercapnia increased tracheal pressure and phrenic nerve activity. Intravenous atropine pretreatment or vagotomy abolished the changes in tracheal pressure without affecting phrenic nerve discharge. Rapid cooling of the intermediate area reversed the tracheal constriction produced by hypercapnia. Graded cooling produced a progressive reduction in the changes in maximal tracheal pressure and phrenic nerve discharge responses caused by hypercapnia. Cooling the intermediate area to 20 degrees C significantly elevated the CO2 thresholds of both responses. These findings demonstrate that structures near the intermediate area of the VMS play a role in the neural cholinergic responses of the tracheal segment to CO2. It is possible that neurons or fibers in intermediate area influence the motor nuclei innervating the trachea. Alternatively, airway tone may be linked to respiratory motor activity so that medullary interventions that influence respiratory motor activity also alter bronchomotor tone.

Download Full-text

Role of adrenal catecholamines in cerebrovasodilation evoked from brain stem

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1987.252.6.h1183 ◽

1987 ◽

Vol 252 (6) ◽

pp. H1183-H1191

Author(s):

C. Iadecola ◽

P. M. Lacombe ◽

M. D. Underwood ◽

T. Ishitsuka ◽

D. J. Reis

Keyword(s):

Brain Function ◽

Blood Gases ◽

Brain Regions ◽

Elevated Plasma ◽

Regional Cerebral Blood ◽

Medullary Reticular Formation ◽

Alpha Chloralose ◽

The Brain ◽

Stimulation Of

We studied whether adrenal medullary catecholamines (CAs) contribute to the metabolically linked increase in regional cerebral blood flow (rCBF) elicited by electrical stimulation of the dorsal medullary reticular formation (DMRF). Rats were anesthetized (alpha-chloralose, 30 mg/kg), paralyzed, and artificially ventilated. The DMRF was electrically stimulated with intermittent trains of pulses through microelectrodes stereotaxically implanted. Blood gases were controlled and, during stimulation, arterial pressure was maintained within the autoregulated range for rCBF. rCBF and blood-brain barrier (BBB) permeability were determined in homogenates of brain regions by using [14C]iodoantipyrine and alpha-aminoisobutyric acid (AIB), respectively, as tracers. Plasma CAs (epinephrine and norepinephrine) were measured radioenzymatically. DMRF stimulation increased rCBF throughout the brain (n = 5; P less than 0.01, analysis of variance) and elevated plasma CAs substantially (n = 4). Acute bilateral adrenalectomy abolished the increase in plasma epinephrine (n = 4), reduced the increases in flow (n = 6) in cerebral cortex (P less than 0.05), and abolished them elsewhere in brain (P greater than 0.05). Comparable effects on rCBF were obtained by selective adrenal demedullation (n = 7) or pretreatment with propranolol (1.5 mg/kg iv) (n = 5). DMRF stimulation did not increase the permeability of the BBB to AIB (n = 5). We conclude that the increases in rCBF elicited from the DMRF has two components, one dependent on, and the other independent of CAs. Since the BBB is impermeable to CAs and DMRF stimulation fails to open the BBB, the results suggest that DMRF stimulation allows, through a mechanism not yet determined, circulating CAs to act on brain and affect brain function.

Download Full-text

Vagal neuroeffector mechanisms affecting transpulmonary pressure in the intact rat

Journal of Applied Physiology ◽

10.1152/jappl.1995.79.4.1233 ◽

1995 ◽

Vol 79 (4) ◽

pp. 1233-1241 ◽

Cited By ~ 3

Author(s):

J. R. Haselton ◽

A. Y. Reynolds ◽

H. D. Schultz

Keyword(s):

Smooth Muscle ◽

Untreated Control ◽

Vagal Stimulation ◽

Muscle Tone ◽

Transpulmonary Pressure ◽

Bilateral Stimulation ◽

Vagus Nerves ◽

Prostaglandin F2 Alpha ◽

Combined Administration ◽

Stimulation Of

Experiments were conducted with chloralose-urethan anesthetized rats to assess the effects of 1) bilateral stimulation of the cervical vagus nerves and 2) parasympathomimetic and sympathomimetic agents. Transpulmonary pressure (Ptp) was used as an index of airway smooth muscle tone, and peak inspiratory Ptp (Ptppeak) values were used for a comparison of responses. In untreated animals, vagal stimulation elicited an increase in Ptppeak of 155%. Cooling of the vagus nerves to 15 degrees C abolished the response of Ptppeak to vagal stimulation. Although isoproterenol (1–10 micrograms/kg i.v.) did not alter resting Ptppeak, it did prevent vagal stimulation from evoking an increase in Ptppeak. Nadolol (1.5 mg/kg i.v.) augmented the increase in Ptppeak elicited by vagal stimulation. Vagal stimulation did not evoke any change in Ptppeak after the administration of both nadolol and atropine or after combined administration of nadolol, atropine, and either serotonin aerosol or prostaglandin F2 alpha. In rats pretreated with capsaicin 1 wk before the experiment, vagal stimulation evoked an increase in Ptppeak that was not statistically different from that of untreated control animals. Therefore, nonadrenergic noncholinergic systems did not appear to play an independent role in the response of the airways to the activation of the vagus nerves.

Download Full-text