Cranial Thyroid Artery Research Articles

Influence of Ouabain on the Tracheal Musculature of the Dog

The effects of ouabain on the smooth muscles of the airway were investigated in anesthetized, paralyzed and artificially ventilated mongrel dogs. Ouabain (30 μg/kg, i.v.) caused a constriction of the tracheal smooth muscle which was followed by bradycardia. When ouabain was infused at a rate of 2 μg/kg/min (i.v.), the tracheal constriction was induced by a total dose of 45.0±5.5 μg/kg, while the bradycardia appeared with a total dose of 54.4±6.1 μg/kg. The ouabain-induced tracheal constriction was inhibited by bilateral vagotomy. The tracheal constriction induced by i.a. infusion of 10 μM ouabain into the bilateral cranial thyroid arteries was inhibited by bilateral vagotomy, but it was not completely blocked. With bilateral vagotomy, the tracheal constriction induced by i.a. infusion of ouabain was unaffected by 3 μM hexamethonium, but it was significantly inhibited by 1 μM atropine. These results suggest that ouabain may induce tracheal constriction by a neurogenic action in addition to its action via the augmentation of the vagal reflex, and the neurogenic action of ouabain may be related, in large part, to the release of acetylcholine from the presynapses of vagus nerves in dogs.

Involvement of .ALPHA.2-adrenergic receptors in the vagal reflex-induced tracheal constriction.

The effects of clonidine on the vagal reflex-induced tracheal constriction have been investigated in anesthetized, paralyzed, and artificially ventilated mongrel dogs. The cervical trachea was transected in situ into two parts. Responses of the tracheal musculature were measured as changes in the intratracheal pressure on an air-filled balloon introduced into the rostral side of the transected trachea. Reflex tracheal constriction was induced by afferent electrical stimulation at the central cut end of the vagus nerve. Drugs were injected or infused close intraarterially (i.a.) into the bilateral cranial thyroid arteries in such a way that each drug was applied just to the rostral trachea. The reflex tracheal constriction was abolished by a close i.a. infusion of 3 microM atropine. The magnitude of the reflex tracheal constriction was slightly reduced by a close i.a. infusion of 10 microM clonidine and was significantly reduced by the infusion of clonidine at a concentration of 100 and 300 microM. The response to 100 microM clonidine was antagonized by a close i.a. infusion of 1 microM yohimbine. The tracheal constriction induced by i.a. injection of 5.5 nmol acetylcholine was unaffected by infusion of 10, 100 and 300 microM clonidine. The vagal reflex-induced tracheal constriction seems to be inhibited by stimulation of prejunctional alpha 2-adrenoceptors.

Evidence that tracheal smooth muscle tone in guinea-pig is unaffected by overflow of noradrenaline released by perivascular nerve fibres.

1. Fluorescence histochemical techniques demonstrated that in the guinea-pig the cervical common carotid, cranial thyroid and caudal thyroid arteries were surrounded by a rich plexus of adrenergic nerve fibres. 2. The superior cervical ganglia were the source of the perivascular adrenergic fibres of the cranial thyroid arteries and the anterior half of the cervical common carotid arteries. These ganglia may also provide some of the perivascular adrenergic fibres of the caudal thyroid arteries. 3. Perivascular stimulation of the cranial thyroid and caudal thyroid arteries failed to elicit a response from isolated extrathoracic tracheal tube preparations. This suggests that it is unlikely that the guinea-pig extrathoracic trachealis muscle is innervated by adrenergic fibres arising from these perivascular plexuses or that overflow of noradrenaline from perivascular nerves causes dilatation of the trachealis muscle.

Secretagogue action of adenosine in the in vivo canine tracheal mucus model.

Adenosine injected via the cranial thyroid artery route into canine tracheas was a very potent and quick acting secretagogue in a unique model of mucus production. It is not known if adenylate cyclase activation was involved, but adenosine caused a statistically significant, dose related enhancement over baseline secretion rates in seventeen mongrel dogs (0.01 mg 18.4 +/- 5.04% increase N.S.; 0.1 mg 62.5 +/- 9.00% P less than 0.001; and 1.0 mg 91.2 +/- 14.1% P less than 0.001). The response was complete in less than two minutes and muscle relaxation usually accompanied the response. Adenosine activation of submucosal glands, mast cells or airway tissue may mean that adenosine is an agonist in pathophysiological abnormalities of the airways.

Regulation of canine mucus secretion by a novel leukotriene synthesis inhibitor (U-60,257).

A novel leukotriene synthesis inhibitor, piriprost (U-60,257) was characterized in three quantitated assays of secretion in the canine in vivo trachea. The normal baseline secretion rate was inhibited in a dose-related fashion when the inhibitor was given via the cranial thyroid artery (decrease compared to control dogs: 27 +/- 3.11% at 0.1 mg, n = 3, p less than 0.05; 56 +/- 4.85% at 0.5 mg, n = 3, p less than 0.01; 61.5 +/- 6.8% at 1.0 mg, n = 14, p less than 0.001). Hypoxia gas mixtures (8% O2 and 92% N2 4 min) delivered into the lung caused a mean increase in secretion of 160 +/- 11.2% (p less than 0.05). When the leukotriene inhibitor (1.0 mg) was given into the close arterial segment before hypoxia, this increased secretion response was blocked (160 +/- 11.2 to 40 +/- 16.7%; p less than 0.05). Finally, arachidonic acid caused a potent and long-lasting enhancement in secretion (179 +/- 9.0% of control; p less than 0.01) that was partially blocked by 5 mg/kg indomethacin 30 min before (90 +/- 12.7% of arachidonic acid; p less than 0.01), and when 1.0 mg U-60,257 preceded the arachidonic acid, an additional inhibition of 50% of the indomethacin inhibition was seen (p less than 0.01; n = 14). These findings are consistent with the hypothesis that canine secretion is modulated by arachidonic acid metabolites that act as agonists for secretion both by the cyclooxygenase and lipoxygenase pathways.

Diphenhydramine blocks the leukotriene-C4 enhanced mucus secretion in canine trachea in vivo.

Leukotrienes (C4, D4) have been shown to enhance mucus secretion in both isolated human airway tissue and intact canine trachea in vivo. They also have been implicated as putative mediators in several airways diseases. In previous canine studies the mucus enhancing effect of leukotriene-C4 was blocked by atropine, FLP 55,712, and hexamethonium but not by cutting the superior laryngeal and vagus nerves. We anesthetized mongrel dogs with chloralose (100 mg/kg) and urethane (500 mg/kg) and ventilated them on a pump. To visualize the secretions from submucosal glands, we exposed the mucosa of the upper trachea and coated its surface with powdered tantalum. Secretions from the glands formed elevation in the tantalum layer (hillocks) with time: the number of tracheal hillocks (an index of mucus secretion) was measured at one or more of the four time points on six dogs after each treatment of the treatment sequence: no LTC4, LTC4, no LTC4 + blocker, and LTC4 + blocker. The potential blocker was diphenhydramine, an H1 antagonist for histamine. LTC4 was injected into the cranial thyroid artery which directly feeds the tracheal segment. We observed hillocks through a dissecting microscope, and the number of hillocks per 1.2 cm2 were counted for a 1-4 min interval. In 6 dogs with 12 responses, LTC4 (10 micrograms) gave a positive response that was significantly different from control (p less than 0.01-0.05) at 2-4 min. Diphenhydramine (n = 6), 0.5 mg/kg, a dose which blocked a histamine challenge without blocking an acetylcholine challenge of secretion, gave a statistically significant (p less than 0.01-0.05) reduction in mucus secretion at 1-4 min. These results support the conclusion that leukotriene C4 induces mucus secretion in dogs that is blocked by prior diphenhydramine administration. This would indicate histamine has a role, but as yet an unknown mechanism in the action of leukotriene-C4 in enhancing mucus.

Leukotriene-C 4 enhances mucus production from submucosal glands in canine trachea in vivo

Because leukotrienes have been implicated as putative mediators in upper airways disease, we studied whether leukotriene C 4 (LTC 4) might also have a mucus enhancing effect on submucosal glands. We anesthetized mongrel dogs with chloralose (100 mg/kg) and urethane (500 mg/kg) and ventilated them on a pump. To help visualize the secretions from submucosal glands, we exposed the mucosa of the upper trachea and coated its surface with powdered tantalum. Secretions from the glands (hillocks) were measured with time: The number of hillocks was measured at four time points on 19 dogs after each treatment in the sequence: no LTC 4, LTC 4, no LTC 4 and LTC 4 + blocker. The potential blockers were nerve cutting, atropine, FPL-55, 712, and hexamethonium. Each potential blocker was used on 3–5 dogs. LTC 4 was injected into the cranial thyroid artery. In 19 dogs with 27 responses, LTC 4(8.6–11.0 μg) gave a positive response that was significantly different from control ( P < 0.01) at 1–4 min. These effects were not abolished in 5 dogs by cutting the superior laryngeal (SLN) and the vagus nerves ( P < 0.01). Pretreatment of the dogs ( n = 5) with atropine, hexamethonium and the specific SRS-A (LTC 4) antagonist FPL 55,112 ( n = 3) gave a significant ( P < 0.01–0.05) reduction in mucus secretion at all times for atropine, hexamethonium, and at all times except 4 min for (FPL 55,712). These results indicate that leukotriene C 4 induces mucus secretion in dogs. This secretion does not depend on an intact reflex pathway but is altered at the individual gland by agents which block ganglionic motor pathways.

Inhibition of parathyroid hormone secretion by 25-hydroxycholecalciferol and 24,25-dihydroxycholecalciferol in the dog.

We studied the effects of vitamin D metabolites on parathyroid hormone (PTH) secretion. Test materials were injected into the cranial thyroid artery of the dog, and immunoreactive PTH was measured frequently in serum samples from the inferior thyroid vein and the femoral vein. This model for the study of secretion had previously been validated with the use of known modulators on PTH secretion. In control experiments, injection of 100% ethanol, the vehicle in which cholecalciferol (D(3)) metabolites were suspended, resulted in no change in PTH secretion. Likewise, native vitamin D(3), in doses ranging from 250 to 1,250 ng had no effect on PTH secretion. 25-Hydroxycholecalciferol, 25-(OH)D(3), in doses of 125-240 ng, caused complete suppression of PTH secretion. When 24,25-dihydroxycholecalciferol, 24,25-(OH)(2)D(3), was injected in doses of 50-250 ng, suppression of PTH secretion was again complete; in doses of 5 ng, injection of this metabolite resulted in significant but incomplete suppression of secretion. In doses of 50-250 ng, 1,25-(OH)(2)D(3) strongly stimulated PTH secretion, but in a dose of 5 ng this metabolite had no effects. Injection of equal doses of 1,25-(OH)(2)D(3) and 24,25-(OH)(2)D(3) resulted in significant suppression of PTH secretion. Hypocalcemia-induced stimulation of PTH secretion was suppressed by 24,25-(OH)(2)D(3) while hypercalcemia-induced suppression of PTH secretion was stimulated by 1,25-(OH)(2)D(3). In all experiments showing suppression of PTH secretion, peripheral PTH decreased. Arguments are presented for considering the suppressive effects of D(3) metabolites as physiologic modulators. However, this stimulating effect of 1,25-(OH)(2)D(3) occurred only in pharmacologic doses and hence probably has no physiologic relevance.

A method for recording smooth muscle and vascular responses of the blood-perfused dog trachea in situ.

1 A method is described for measuring responses of dog tracheal musculature and vasculature in situ. 2 The upper two thirds of the trachea was perfused with blood through both cranial thyroid arteries at a constant pressure. The blood flow through the arteries was measured with an electromagnetic flowmeter. The response of the tracheal musculature was measured as a change in pressure in a water-filled cuff inserted into the trachea via the mouth. Drugs were injected close-arterially. 3 Acetylcholine produced dose-dependent increases in blood flow rate (vasodilatation) and in tracheal intraluminal pressure (tracheal constriction). These responses were antagonized by atropine. 4 Isoprenaline produced vasodilatation which was blocked by propranolol. Adrenaline and noradrenaline caused vasocontriction which was blocked by phentolamine. 5 All three catecholamines produced a decrease in tracheal intraluminal pressure (tracheal dilatation). The tracheal dilatation in response to adrenaline and noradrenaline was converted to constriction by propranolol. The tracheal constriction thus unmasked was abolished specifically by phentolamine. 6 From these results it is concluded that the tracheal musculature and vasculature contain muscarinic receptors, and excitatory alpha- and inhibitory beta-adrenoceptors. In the tracheal musculature beta-adrenoceptors predominate over alpha-adrenoceptors; the reverse is true in the tracheal vasculature.

Transplantation of the Canine Larynx

Auto-and allotransplantation of the canine larynx were performed. In the autotrans-plantation experiment, the completely excised larynx was replanted in the former place after 1 or 2 hours preservation. In the allotransplantation experiment, the heparinized donor cadaver was preserved in a hypothermic chamber under perfusion from one side of the common carotid arteries which were damped bilaterally at the upper and lower parts of the diverging portion of the cranial thyroid arteries. Following 24 hours storage in this setting, the larynx was removed and transplanted to the recipient. The vessel anastomosis vas performed on the unilateral common carotid artery and on the lingual, facial and external maxillary veins bilaterally. For the nerve anastomosis, the pedicled nerve muscle graft method was deviced, that is, laryngeal nerve pedicled intrinsic laryngeal muscle block was implanted on the corresponding muscle of the transplanted larynx. Temporary tracheotomy was performed and nutrition, antibiotics and immunosuppressive administration were provided by preliminary gastrostomy during the period of intensive care. Endoscopic observation showed almost normal movement of the vocal cords with normal color and tone in 5 weeks after operation and servived over 2 years in the autotransplanted cases and inwards movement of the vocal cords to the paramedian position at the time of phonation in 8 weeks postoperatively in the allotransplanted cases. Azathioprine and steroid were administrated as the immunosuppressive agent. At present, the longest servival time of animals along with their allotransplanted larynges is 65 days.