Respiratory Effects of TRH in Preterm Rabbits

Hedner, Thomas; Hedner, Jan; Jonason, Jan; Lundberg, Dag

doi:10.1203/00006450-198207000-00010

Cited by 16 publications

(9 citation statements)

References 21 publications

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“…Our results are qualitatively similar to those reported in the adult and neonate (3)(4)(5)(6)(7)(8)(9)(10)(11)(12). The onset of breathing was rapid and the rate increased significantly.…”

Section: Discussionsupporting

confidence: 81%

“…TRH administered ten-Oz gas mixture through the solution. This solution remained trally to the adult and preterm neonatal animal stimulates res-stable for UP to 6 h. The TRH solution was then passed through piration (3)(4)(5)(6)(7)(8)(9)(10)(11)(12). This stimulation results from an initial short-a Millipore filter (0.22 pm) and administered as either a 2-or 5-ening of inspiratory time followed by an increase in respiratory W g bolus, in a volume of 1.4 ml, injected slowly over a 5-min rate due to a decrease in expiratory time (7).…”

Section: Methodsmentioning

confidence: 99%

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The Central Effects of Thyrotropin-Releasing Hormone on the Breathing Movements and Electrocortical Activity of the Fetal Sheep

Gluckman

Johnston

1988

Pediatr Res

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ABSTRACT. The fetal respiratory and electrocortical effects of thyrotropin-releasing hormone (TRH) administered into the lateral cerebral ventricles, have been investigated in chronically catheterized unanesthetized fetal sheep at 125-140 days of gestation. Stimulatory effects on fetal breathing movements were seen at doses as low as a lug bolus. TRH given as a 5-pg bolus followed by a 10 pg/ h infusion for 2 h induced a rapid switch to significantly faster, deeper, and continuous fetal breathing movements, while the electrocorticogram remained episodic. Fetal breathing movements did not stop during hypoxia. TRH given as a 2-pg bolus followed by a 4 pg/h infusion or as a 5-pg bolus followed by a 5 pg/h infusion induced the same stimulation of FBMs, but breathing essentially remained episodic, state related and inhibited by hypoxia. As hypothermia presumably induces a surge in TRH secretion at birth it is possible that TRH has some role in the switch from fetal to postnatal breathing patterns. sheep (Romney-Suffolk cross) at 120-130 days gestation under maternal halothane/oxygen anaesthesia, using sterile techniques. Catheters were implanted into a carotid artery, a jugular vein, the trachea, and the amniotic sac. Stainless steel electrodes were implanted bilaterally onto the parietal dura and the nuchal and diaphragm muscles (14). A lateral cerebral ventricle cannula was implanted as previously described (1 3). Fetal catheters were exteriorized through the maternal flank. Vascular catheters were also implanted into a maternal pedal artery and vein. These catheters were exteriorized on the maternal flank close to the fetal catheters. The postoperative care of the ewe and maintenance of the CSF catheter have been described previously (1 3). EXPERIMENTAL PROCEDURESExperiments were conducted at least 5 days postoperatively and were canied out only when the fetal arterial PO2 was higher than 18.0 mm Hg and fetal arterial pH was more than 7.32. Only one experiment a day was conducted. The gestational age at which fetuses were studied ranged between 125 to 140 days.All infusions were performed using a CSF pH, after dissolution of TRH, of 7.34-7.38 (13). The CSF catheter dead-space was 0.7 ml. The control experiments consisted of a 1.4 ml bolus followed by a 1.0 ml/h infusion of artificial CSF for 2 h, over a pH range of 7.34-7.38. The control for bolus alone experiments was the administration of a 1.4-ml bolus of CSF as previously described (1 3). These experiments were performed inseven fetbses. As an additional check the lateral ventricle cannula was flushed with filtered artificial CSF 1-2 h before each experiment.TRH (L-pyroglutamyl-L-histidyl-L-prolinamide Sigma Chem-TRH has been found to exist throughout the nervous system ical CO.) Was diluted appropriately with artificial CSF and the including areas of the brain stem known to contain nuclei PH checked and adjusted if necessary by bubbling 5% C02/95% involved in respiratory control (1-3). TRH administered ten-Oz gas mixture through the solution. This solution re...

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“…Our results are qualitatively similar to those reported in the adult and neonate (3)(4)(5)(6)(7)(8)(9)(10)(11)(12). The onset of breathing was rapid and the rate increased significantly.…”

Section: Discussionsupporting

confidence: 81%

Section: Methodsmentioning

confidence: 99%

The Central Effects of Thyrotropin-Releasing Hormone on the Breathing Movements and Electrocortical Activity of the Fetal Sheep

Gluckman

Johnston

1988

Pediatr Res

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“…After cessation o f respiratory movements, a graded 2-ml syringe was connected to the external fitting of the tra cheal cannula and a stepwise (0.1,0.2 and 0.4 ml) cal ibration of VT was performed. Respiratory time inter vals, inspiratory time (T|), expiratory time (TE) and total cycle duration (TTOt) were calculated from the respiratory curve at low chart speed as previously described [12]. In order to get an estimate for central nervous respiratory activity, 'inspiratory drive' and 'respiratory timing'.…”

Section: Methodsmentioning

confidence: 99%

“…serotonin, GABA and enkephal ins) [6,7,10,23] and stimulating (e.g. dopa mine, substance P and TRH) [8,9,11,12,21 ] systems as previously proposed [6].…”

Section: Introductionmentioning

confidence: 99%

Effects of GABA and Some GABA Analogues on Respiratory Regulation in the Preterm Rabbit

Hedner¹,

Hedner²,

Bergman³

et al. 1983

Neonatology

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Preterm neonatal rabbits (gestational age 29 days) were given GABA (750 mg/kg) or the GABA-like drugs muscimol (2 mg/kg) and GHBA (375 mg/kg) intraperitoneally. Basal respiration and the ventilatory response to 10% CO₂ were studied, before and after drug administration, in a whole body plethysmograph during halothane anesthesia. The three drugs tested all caused a decrease in minute volume. The decrease in minute volume was mainly due to a decrease in tidal volume after GABA and muscimol, while GHBA reduced minute volume due to a decrease in respiratory frequency. A decrease in respiratory frequency was also seen after muscimol administration. Changes in the respiratory time intervals were seen after muscimol and GHBA both causing significant increases in expiratory and respiratory time. ‘Inspiratory drive’ and ‘respiratory timing mechanisms’ were evaluated by V_τ/T_I and T_ι/T_TOT, respectively. GABA and muscimol reduced both V_T/T_I and Tι/T_TOT while GHBA only reduced T_I/T_TOT Addition of 10% CO₂ to the inhalation gas caused an increase in tidal volume and minute volume during control conditions. This response to CO₂ was abolished by GABA and GHBA treatment. Our findings demonstrate that GABA and GABA-like drugs cause respiratory depression in the preterm neonate. Central mechanisms are most likely involved in this response. These findings may be relevant to the irregular or apneic breathing sometimes seen in the preterm human infant.

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“…Apart from its hypophysiotrophic effects, TRH functions as a ubiquitous neurotransmitter, and is known to cause profound neurobehavioural arousal and stimulate breathing in both neonatal and fetal experimental animals [8][9][10], seemingly via sympathetic activation. Additional effects seen after direct intravenous administration in fetal sheep include electrocortical desynchronization, an increase in body and eye movements, more rapid and deeper breathing movements, and a transient bradycardia followed by prolonged tachycardia [8].…”

Section: Introductionmentioning

confidence: 99%

Effects of Antenatal Thyrotropin-Releasing Hormone on Fetal Heart Rate and Breathing Movements

Peek

Bajoria²,

Talbert³

et al. 1998

Fetal Diagn Ther

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Objective: To determine the effect of maternally administered thyrotropin-releasing hormone (TRH) on fetal heart rate (FHR) pattern and fetal breathing movements (FBM). Methods: Prospective observational study of 75 pregnant women between 26 and 34 weeks’ gestation in whom pharmacological fetal lung maturation was clinically indicated. Forty-minute recordings were made of FBM or FHR patterns before and after drug administration. Twenty-five received TRH 400 µg as an intravenous bolus, 25 TRH 400 µg in 50 ml 0.9% saline as an intraveous infusion, and 25 acted as controls. Recordings were processed digitally to calculate the change in FHR (n = 45) and FBM parameters (n = 30). The main outcome measures for FHR were number of accelerations and decelerations, baseline rate, overall and short-term variation and duration of high and low variability, while for FBM they were rate, breath-to-breath interval and incidence. Results between groups were compared by analysis of variance. Results: There was no significant change in FHR, accelerations or variation in any of the groups. Similarly, there was no change in the incidence of FBM. TRH administered as a bolus produced a small statistically but not clinically significant increase in breathing rate (mean Δ = 35 breaths/h, p = 0.004), which was not seen in the TRH infusion and control groups. Conclusions: Maternally administered TRH as used to enhance fetal lung maturation has no clinically significant direct effect on FHR or FBM patterns.

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Respiratory Effects of TRH in Preterm Rabbits

Cited by 16 publications

References 21 publications

The Central Effects of Thyrotropin-Releasing Hormone on the Breathing Movements and Electrocortical Activity of the Fetal Sheep

The Central Effects of Thyrotropin-Releasing Hormone on the Breathing Movements and Electrocortical Activity of the Fetal Sheep

Effects of GABA and Some GABA Analogues on Respiratory Regulation in the Preterm Rabbit

Effects of Antenatal Thyrotropin-Releasing Hormone on Fetal Heart Rate and Breathing Movements

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