In this paper we present the flow research of the development of receptor bronchial system in the first month of extra-uterine life up to the sixth month of development, performed by tracking the reactions of isolated tracheal rings in acetylcholine (Ach), propranolol (P), histamine (Hist), and prostaglandin (PGF2-alfa) in concentrations of: 10-4, 10-3, 10-2 and 10-1 mol/dm3; in piglets of ages: 1 month, 2 months, 4 months and 6 months. Results shows that Ach causes reaction of smooth muscles from the first month of extra-uterine life (p < 0.01) and that Propranolol (P) significantly emphasizes the effect of Ach (p > 0.1), while histamine and PGF2-alpha do not cause constriction (histamine up to 4 months of age, PGF2-alfa up to 6 months of extra-uterine life). This shows that cholinergic and adrenergic system in piglet airways is developed during intrauterine life and reaction can be registered in the first month of extra-uterine life, while other receptor systems are developed in later periods of extra-uterine life. This suggests that lack of reaction of tracheal smooth musculature (TSM) comes as a result of sufficient non-maturity of mast cells from which chemical mediators, with local functioning, are released.

The role of meconium in the respiratory system was studied in newborns, who died from various causes (250 up to 3000 g of weight). We monitored tracheal rings response to dopamine, serotonin and ethanol in different concentrations (dopamine: 0,05 mg/ml, 0,5 mg/ml, 5 mg/ml; serotonin (5-HT): 10-4, 10-3, 10-2, 10-1 mol/dm3; ethanol: 0,02 ml, 0,5 ml, 1,0 ml; 96%). Tracheal smooth musculature tonus (TSM) was examined in 48 tracheal preparations taken after the newborn exitus due to different reasons. Based on functional researche of isolated preparations of tracheas, it may be concluded that: aspiration of meconium has not changed the response of TSM to dopamine, serotonin and ethanol (p>0,1) in comparison with the control group, which have died due to different lung inflammatory processes (e.g. pneumonia, bronchopneumonia, atelectasis, cerebral hemorrhage). The results suggest that meconium does not potentiate the constricting action of dopamine, serotonin and ethanol in tracheobronchial system. Meconium causes mild relaxation of the TSM through a mechanism that is not intermediated by the products of cyclooxygenases (prostaglandins, prostacyclins) from the tracheal epithelium or proteins. Also, as it seems, the direct activity of many tested acids in the smooth musculature has no significant impact on increase of the airways tonus in MAS syndrome.

Actions of acetylcholine (ACh), histamines, serotonins (5-HT) and prostaglandins (PGF2-alfa) in concentrations of 10(-4), 10(-3), 10(-2) and 10(-1) mol/dm(3) were analyzed in vitro conditions in isolated specimens of tracheas of 24 pigs, 7 guinea pigs, and dead persons for different reasons (8), in the presence and without presence of propranolol. Whilst, research regarding actions of aerosolized histamines (10 mg, 1%, 2 min), in the presence and without the presence of aerosolized propranolol (20 mg, 2%, 2 min) was done in vivo in 6 healthy persons. Study results show that propranolol does not emphasize contraction of the airways smooth musculature as induced by ACh, histamine, 5-HT and PGF2-alfa in vitro conditions (p>0,1). Also, in vivo we found a non-significance of tracheal smooth musculature constriction (p>0,1).

The development of neuron cells in vagal nerve nuclei in medulla oblongata was studied in vitro in live newborns and stillborns from different cases. Morphological changes were studied in respiratory nuclei of dorsal motor centre (DMNV) and nucleus tractus solitarius (NTS) in medulla oblongata. The material from medulla oblongata was fixated in 10 micro buffered formalin solution. Fixated material was cut in series of 10mu thickness, with starting point from obex in +/- 4 mm thickness. Special histochemical and histoenzymatic methods for central nervous system were used: cresyl echt violet coloring, tolyidin blue, Sevier-Munger modification and Grimelius coloring. In immature newborns (abortions and immature) in dorsal motor nucleus of the vagus (DMNV) population stages S1, S2, S3 are dominant. In neuron population in vagal sensory nuclei (NTS) stages S1, S2 are dominant. In more advanced stages of development of newborns (premature), in DMNV stages S3 and S4 are seen and in NTS stages S2 and S3 are dominant. In mature phase of newborns (maturity) in vagal nucleus DMNV stages S5 and S6 are dominant, while in sensory nucleus NTS stages S4 and S5 are dominant. These data suggest that neuron population in dorsal motor nucleus of the vagus (DMNV) are more advanced in neuronal maturity in comparison with sensory neuron population of vagal sensory nucleus NTS. This occurrence shows that phylogenetic development of motor complex is more advanced than the sensory one, which is expected to take new information's from the extra uterine life after birth (extra uterine vagal phenotype).

Morphological aspect of tracheal preparations and pulmonary tissue was studied in vitro. The material was obtained from autopsy of newborns that died from different causes. Examinations were made in different gestational periods (immature 23-29 weeks; premature 30-37 weeks; mature >38 weeks). Material for examination was obtained up to 6 hours after death. Pulmonary and tracheal tissue was incubated for fixation in buffered formalin (10%). Special histochemical and histoenzymatic methods were used for coloring of pulmonary and tracheal tissue and the activity of ATP-ase and dopaoxidase was monitored. Cut out models were made in series of 7μ, 10 μ and 20 μ. In peripheral axons of tracheobronchial pathways, degenerative alterations of adrenergic nerve endings in lung inflammatory processes were documented. These morphologic neuronal changes were described: Walerians degeneration, neuro-axonal degeneration and segment demyelinisation. These changes are well seen with argentafine coloring (Sevier-Munger modification for nerve endings) and with dopaoxidase reaction. In mature newborns that died from respiratory distress syndrome, we found different forms of metabolic and toxic degenerative damage in peripheral axons, such as: segment demyelinisation, neurotubular fragmentation, Schwan cell proliferation, fragmentation and bulging out of axonal neurotubules and neurofilaments. In tracheo-bronchial tissue, chromafine granules are homogenously distributed on Lamina propria layer and through glandular structures. This gives as a contradiction, according to some authors, that adrenergic nerve fibers for muscle tissue are absent and that adrenaline and noradrenalin diffuse in muscle tissue from interstice.

Morphological aspect of tracheal preparations and pulmonary tissue was studied in vitro. The material was obtained from autopsy of newborns that died from different causes. Examinations were made in different gestational periods (immature 23-29 weeks; premature 30-37 weeks; mature >38 weeks). Material for examination was obtained up to 6 hours after death. Pulmonary and tracheal tissue was incubated for fixation in buffered formalin (10%). Special histochemical and histoenzymatic methods were used for coloring of pulmonary and tracheal tissue and the activity of ATP-ase and dopaoxidase was monitored. Cut out models were made in series of 7 micro, 10 micro and 20 micro. In peripheral axons of tracheobronchial pathways, degenerative alterations of adrenergic nerve endings in lung inflammatory processes were documented. These morphologic neuronal changes were described: Walerians degeneration, neuro-axonal degeneration and segment demyelinisation. These changes are well seen with argentafine coloring (Sevier-Munger modification for nerve endings) and with dopaoxidase reaction. In mature newborns that died from respiratory distress syndrome, we found different forms of metabolic and toxic degenerative damage in peripheral axons, such as: segment demyelinisation, neurotubular fragmentation, Schwann cell proliferation, fragmentation and bulging out of axonal neurotubules and neurofilaments. In tracheo-bronchial tissue, chromafine granules are homogeneously distributed on Lamina propria layer and through glandular structures. This gives as a contradiction, according to some authors, that adrenergic nerve fibers for muscle tissue are absent and that adrenaline and noradrenaline diffuse in muscle tissue from interstice.

Research was done on pharmacological-physiological development of the bronchial receptor system on the smooth muscles of trachea in the newborn children, alive-born and stillborn children. Monitored was the response on: acetylcholine, dopamine, histamine and serotonin in different molar concentrations 10(-4), 10(-3), 10(-2), 10 mol/dm(-3), micromol/dm(-3)). Research was done on tonus of tracheal smooth muscles of 23 tracheal preparations taken by autopsy after death from different factors. Based on pharmacological-physiological research on the preparations of human isolated trachea it was find out that: acetylcholine stimulation effect is significant (p>0,01) in 38-41 weeks of pregnancy comparing with that in 30-37 weeks of pregnancy (p>0,01), while dopamine stimulation effect is significant (p>0,05) in 30-37 pregnancy weeks comparing with the effect of acetylcholine and dopamine on the still-born infants of the same pregnancy period (p<0,01). Histaminic receptors were developed during intrauterine life after 38 weeks of pregnancy (p>0,025). Serotonin has caused contraction of the bronchial smooth muscles after 30 pregnancy weeks, but response was not significant (p<0,01). This suggests that cholinergic and adrenergic system of the airways in alive newborn infants develops in parallel intrauterine, contrary to other systems which develop in certain extrauterine life phases.

Morphologic growth of cholinergic bronchial respiratory system was examined at live and dead newborns. Tracheal smooth musculature was examined at 18 experimental preparations taken by the autopsy after exiting from different factors. Samples were divided into three groups based on gestational weeks. First group: from 23-29 gestational weeks (immature, N=5); second group: from 30-37 gestational weeks (premature, N=7); third group: from 38-41 gestational weeks (mature, N=6). Based on morphological examination of isolated preparations human trachea fingings are the following: in 23-29 week are found nerve endings with axo-axonal synapses mainly at ramification phase of lungs blood vessels net, without trachea bronchial innervations with axo-axonal synapses, and with perichondrial localization. In 30-37 gestational weeks axo-xonal synapses are found in between glands acinus's and vessels net, and also emphatic choline reactivity at lung ganglions: this suggests existing of cholinergic system at alive newborns. At 38-41 gestational weeks exists a wealthy nerve neuromuscular net in smooth tracheal musculature with different vesicles. Choline reactivity is emphasized peri and intrachondrial at lamina propria, at most around sensory glands and in smooth musculature. This suggests that there is no choline reactivity at epithelium and of existence of cholinergic system in tracheal bronchial smooth musculature.