V. A. Safonov

Effect of phenibut on the formation of the respiratory rhythm

In experiments with Nembutal-anesthetized cats of both sexes, the drug phenibut administered intravenously was found to elicit periodic apneic respiration and to rank between baclofen and sodium oxybutyrate in terms of the ability to disrupt the respiratory rhythm. It is suggested that these three activators of the gamma-aminobutyric acid (GABA) system produce differential effects on GABAB receptors (baclofen>phenibut>oxybutyrate in order of decreasing effectiveness) and participate in the formation of the respiratory rhythm, and that in activating this system they can give rise to irregular slowed respiration with pauses at inspiration.

Respiratory and circulatory disorders in experimental poisoning with an organophosphorus pesticide

Acute poisoning with Anthio is associated with a gradual drop of blood pressure in the greater circulation and the development of intensive metabolic acidosis, despite normoxia still observed in the arterial blood and a somewhat increased oxygen capacity of the blood, this indicating mitochondrial injury and disordered tissue respiration.

Effects of an Organophosphorus Compound on Pulmonary and Systemic Circulations

Shortly (30–90 min) after an intragastric administration of the organophosphorus pesticide Anthio to cats, their cardiac output begins to decrease and the right ventricular output decreased to a greater extent than the left. Blood is redistributed to the greater circulation with a diminution of blood flow in the pulmonary lobar vessels.

Influence of general anesthesia on acute experimental poisoning of cats with the organophosphorus pesticide Anthio

It is shown that general anesthesia strongly influences the resistance of animals to poisoning with organophosphorus compounds (OPC) such as Anthio, weakens compensatory/adaptive responses, and possibly acts synergistically with OPC in impairing tissue respiration. One to three days after peroral administration of Anthio, reduced oxygen tension in arterial blood and increased heart and respiratory rates were recorded in cats, although the arterial blood pressure tended to drop markedly. Anthio poisoning led to profound changes in the autonomic regulation of functions, which was manifested in sharply decreased parasympathetic influences. The function of the brains GABA-ergic system did not change appreciably.

Effect of Opioids on Mechanoreflexive Respiration Control

The effects of opioids (morphine and fentanyl) on the function of mechanoreceptive respiration regulatory loop were demonstrated. In most opioid-treated rats (74% cases) vagotomy was followed by apneustic respiration with inspiration pause. Excess of opioids in rat CNS produced minor disturbances in the respiration rhythm, but in the absence afferent input from the mechanoreceptors of respiratory pathways and lungs, pronounced periodic apneustic respiration with inspiration pauses developed. The opioidergic system is involved in the formation of respiratory rhythm, but had no appreciable effect on transmission of mechano-receptive nerve pulses from respiratory pathways and the lungs to the respiratory center.

Effects of Electrical Stimulation of Respiratory Center in the Event of Termination of Its Natural Rhythmic Activity

The possibility of restoration of the natural rhythmic activity of the respiratory system by transcutaneous electrical stimulation of the respiratory center after termination of spontaneous respiratory movements caused by narcosis was shown in experiments on mongrel cats of both sexes under nembutal anesthesia. Natural rhythmic activity of respiratory center was stopped by additional administration of sodium thiopental. The proposed method of electrical stimulation of the respiratory center allows maintaining the rhythmic respiratory movements and their recovery after narcotic apnea up to complete recovery of spontaneous respiration.

Effects of GABAmimetics on chemoreceptor regulation of respiration

Changes in chemosensitivity of the respiratory system to oxygen and carbon dioxide induced by a GABAmimetic lithium hydroxybutyrate were studied on narcotized rats. In the majority of animals (56%), this activation of GABA receptors caused periodic apnea. The sensitivity of the respiratory system to hypercapnia sharply decreased (or completely disappeared) 30–45 min after intravenous injection of lithium hydroxybutyrate, while the sensitivity to oxygen was preserved. In rats, as well as in cats, GABAmimetics can readjust the chemoreceptor circuit from respiratory CO2-dependent to O2-dependent regulation.

Sensitivity of the respiratory system to pulmonary mechanoreceptor impulses during GABAergic system activation

Acute experiments on narcotized cats show that systemic administration of the GABA receptor agonist sodium hydroxybutyrate and fenibut (phenylbutyrate) during periodic apneustic breathing and subsequent engine-like breathing reduces sensitivity of the respiratory system to afferentation from lung stretch receptors. Preliminary vagotomy does not promote the transformation of periodic apneustic breathing to engine-like breathing in response to injection of GABA agonists.

Effects of calcium and its antagonists on hemodynamics and respiration

Acute tests on cats under Nembutal anesthesia show that intravenous injection of Ca2+ causes pathological respiration of the apneustic type and slight rises in pulmonary and arterial pressures. The calcium channel blockers verapamil and nifedipine decrease the amplitude of respiratory movements, increase the respiration rate and pulmonary pulse pressure, and lower systemic pressure. The introduction of verapamil or nifedipine into the fourth ventricle of the brain does not alter respiration or hemodynamics, whereas the introduction of Ca2+ leads to irreversible respiratory standstill. Hemodynamic parameters decrease 2–3 min after the respiratory standstill.

Lipid peroxidation after acute intoxication of cats with anthio and the effect of ionol on their survival

Acute intoxication with the organophosphorus pesticide Anthio considerably increases the intensity of lipid peroxidation in Nembutal-anesthetized cats. Pretreatment with the synthetic antioxidant ionol prolongs the survival of the cats. Ionol has no appreciable effect on respiratory and hemodynamic parameters. Lipid peroxidation may contribute to the disturbances caused by Anthio.