[The effect of cyclic nucleotides on the rhythmogenicity of the lymphatic center in the frog Rana temporaria]. / Vliianie tsiklicheskikh nukleotidov na ritmogenez limfaticheskogo tsentra liagushki Rana temporaria.

Studies have been made of the effect of cAMP on the spontaneous impulse activity of lymphatic pacemaker neurons in the frog. It was shown that inhibition of phosphodiesterases by papaverine and 3-isobutyl-1-methylxanthin resulted in the increase in rhythm of bursting impulse activity of the lymphatic centre turning it into a continuous one. The same effect was produced by dibutyryl-cAMP, and to a lower extent--by cAMP. CGMP blocked rhythmic activity of the centre. Possible role of cyclic nucleotides in rhythmic activity of pacemaker cells in the spinal centre of the lymphatic hearts in the frog is discussed.

[Recovery of impaired respiratory activity in cats by thyroliberin analog (PR-546) devoid of hormonal properties]. / Vosstanovlenie narushennoi dykhatel'noi aktivnosti koshek analogom tiroliberina (PR-546), lishennym gormonal'nykh svoistv.

Synthetic analogue thyroliberin (PR-546) devoid of hormonal activity, recovered respiration in conditions of hyperventilation, two-sided vagotomy and hypoxia, caused by the 40-70% bleeding. PR-546 (in doses 100-500 micrograms/kg) intravenously injected was shown to abolish diagram activity decreased effect after hyperventilation. Injection of PR-546 to vagotomized cats in 1.5-2 h, increased breathing rate. The breathing activity resumed after long breaks in respiration as a result of peptide injection. The responses to analogue introductions is similar to the thyroliberin effect.

[Thyroliberin and its analog lacking hormonal properties stimulate respiratory center activity in the frog Rana temporaria]. / Tiroliberin i ego analog, lishennyi gormonal'nykh svoistv, stimuliruiut aktivnost' dykhatel'nogo tsentra u liagushki Rana temporaria.

It has been shown that thyroliberin and its synthetic analogue PR-546 injected into the lymphatic sacs (4.10(-7)-4.10(-9) g/kg) or applied to the medulla oblongata in the bulbar frogs (4.10(-10)-4.10(-12) g/kg) significantly increase the rate of motor respiratory volleys in the hypoglossal nerve. In preparations with the irregular level of the activity of the respiratory center, these drugs enhanced stabilization of the initial level of the rhythm of motor respiratory discharges.

[Recovery from disorders of respiratory activity in cats using thyroliberin]. / Vosstanovlenie narushennoi dykhatel'noi aktivnosti koshek tiroliberinom.

Controlled lung hyperventilation in cats inhibited the activity of the diaphragm muscle with a subsequent stop of respiration after the end of hyperventilation. Thyroliberin (20-30 mg/kg) intravenously was shown to abolish these effects 15-20 min after application. Preliminary introduction of thyroliberin prevented the changes in the respiration rate and depth caused by vagotomy.

[Mechanoreceptor sensitivity of the frog lung to carbon dioxide]. / O chuvstvitel'nosti mekhanoretseptorov legkikh u liagushki k dvuokisi ugleroda.

To reveal CO2-sensitive receptors in the lungs of frogs, studies have been made of the pattern of afferent impulse activity in the pulmonary branch of the vagal nerve in lung preparations during their extension by gaseous mixtures containing 5-8% of CO2. No specific CO2-sensitive chemoreceptors were found. It was found that pulmonary mechanoreceptors exhibit sensitivity to elevated CO2 concentrations which significantly decrease impulse activity in slowly and rapidly adapting mechanoreceptors. It is concluded that the sensitivity of pulmonary mechanoreceptors to CO2 is formed in terrestrial vertebrates at early phylogenetic stages.

[Role of the pulmonary mechanoreceptor apparatus in molding the natural respiration of the frog Rana temporaria]. / Rol' mekhanoretseptornogo apparata legkikh v formirovanii estestvennogo dykhaniia u liagushki Rana temporaria.

In acute experiments on the frog Rana temporaria, studies have been made of the effect of afferent impulsation in pulmonary mechanoreceptors on respiration pattern. Simultaneous recordings were made of total afferent activity in the pulmonary branch of the vagal nerve and of the activity of motor respiratory nerves as an index of respiration pattern. It was shown that to the end of ventilation period, the level of afferentation decreases up to a threshold value which favours the onset of inspiration. Artificial decrease of afferentation level by the increase in CO2 content in the lung or by novocain application to the latter always resulted in extra-inspiration. On vagotomized frogs, it was found that maximum level of afferent influences is necessary for the onset of expiration.

[Participation of cGMP in inhibitory mechanisms of the center of amphibian lymph hearts]. / Ob uchastii tsGMF v mekhanizmakh tormozheniia tsentra limfaticheskikh serdets amfibiii.

The effects of cAMP on generation of spontaneous rhythmic activity of lymphatic pacemaker neurons, was studied in fragments of the frog isolated perfused spinal cord. The cGMP depressed both the rhythm of the burst activity and the dibutyril-cAMP effect. The depressive effect of the cGMP was reversibly blocked with furosemide. The data obtained suggest existence of relationship between GABA-ergic inhibition of the pacemaker activity of lymphatic center and the cGMP concentration in pacemaker neurons.

[Stretch receptors of the lungs in the frog Rana temporaria]. / Restseptory rastiazheniia legkikh u liagushki Rana temporaria.

In experiments on isolated lungs, studies have been made on the activity of single afferent fibers during simulated expiration and inspiration. Both slowly adapting and rapidly adapting voluminous stretch receptors were found in the frog lungs. The latter type exhibits the activity also during fast simulated expiration. Using acetylcholine and histamine, it was shown that the level of excitability of the receptors investigated depends on functional condition of the plain muscles in the pulmonary wall.

[Effect of gamma-aminobutyric acid on neurons of the spinal lymphatic center]. / Deistvie gammaaminomaslianoi kisloty na neirony spinal'nogo limfaticheskogo tsentra.

In the frog isolated perfused 7-11th spinal cord segments with the lymphatic center, GABA inhibited both the activity of pace-maker neurons and the burst-type activity of lymphatic motoneurons. Picrotoxin, bicuculline, ammonia and furosemide reversibly blocked the inhibition induced with GABA. The data obtained suggest existence of GABA-ergic control of the lymphatic center activity in the 9-11th segments of the spinal cord.

[Nature of a mediator participating in reflex inhibition of the activity of the lymphatic center of the frog]. / O prirode mediatora, uchastvuiushchego v reflektornom tormozhenii deiatel'nosti limfaticheskogo tsentra liagushki.

Picrotoxin, bicucullin, ammonia and furosemide reversibly blocked the inhibition induced by electrical stimulation of the 9-10th dorsal roots in the frog spinal cord. The data obtained suggest existence of GABA-ergic neurons regulating the lymphatic centre activity in the 9-11th segments of the frog spinal cord.

[Mechanism of the poststimulation inhibition of the lymphatic center in the frog]. / O mekhanizme poststimuliatsionnogo tormozheniia limfaticheskogo tsentra liagushki.

The nature of post-stimulation inhibition of the frog lymphatic center was compared with characteristics of a primary inhibition of lymphatic center in spinal and bulbar frogs as well as in a preparation of the isolated spinal cord. The inhibitory mechanism under study seems to involve specific neuron-activators. The activity of the latter provides a certain threshold level of the excitability of the lymphatic center's pace-maker.

[Mechanism of the occurrence of evoked motor activity in the lymphatic center of the frog]. / O mekhanizme vozniknoveniia vyzvannoi motornoi aktivnosti limfaticheskogo tsentra liagushki.

In the frog isolated spinal cord, the main parameters of spike activity of the lymphatic center's motoneurons were studied in normal conditions and in altered rhythm of their functioning. Artificial excitation of the lymphatic center by means of stimulation of the dorsal roots, irrespective of the electrical stimuli rate (within the range 1-5 Hz), was shown to induce the same regularities of the evoked motor activity generation in the lymphatic center in the altered rhythm, as in the spontaneous activity of the motoneurons. The main parameters of the evoked activity of motoneurons under these conditions are not significantly dissimilar to the respective parameters of spontaneous activity, either.

[Reflex regulation of the endogenous rhythm of the frog lymphatic center]. / Reflektornaia reguliatsiia éndogennogo ritma limfaticheskogo tsentra liagushki.

The activity of motoneurons in the lymphatic centre of bulbar or spinal frogs, or of isolated fragments of the frog spinal cord remained essentially unchanged in spite of either activating or inhibiting afferent influences which seem to affect special pace-maker neurons in the lymphatic centre leaving motoneurons intact.

[Organization of the rhythmic activity of the spinal center motoneurons of the lymphatic hearts of Rana temporaria frogs]. / Organizatsiia ritmicheskoi aktivnosti motoneironov spinal'nykh tsentrov limfaticheskikh serdets liagushki Rana temporaria

Spontaneous rhythmic impulse discharges of motoneurons of spinal centers of the posterior lymphatic hearts have been recorded from the ventral roots of isolated spinal cord perfused by oxygenated Ringer's solution. Inhibition of the transmission in interneuronal synapses evoked by abolition of Ca ions from the external solution and by the addition to the latter of 1--4 mM EDTA was accompanied by the block of the spontaneous impulse activity. Blocking of rhythmic efferent discharges in the anterior roots was also observed after the addition to normal Ringer's solution of 10--30 mM MgCl2. Inhibition of the spontaneous activity by high Mg content in the perfusion fluid could be alleviated by the addition of 5--15 mM CaCl2 to this solution. Antidromic impulses in the ventral roots of the XI and X segments, evoked by rhythmic electrical stimulation of these roots, did not affect the intrinsic rhythm of motor discharges.