Respiratory activity generated by semi-isolated medullo-spinal preparation and recorded from the phrenic nerve of newborn rats

Marchenko, Vitaliy; Fenik, Victor B.; Preobrazhenskii, N. N.; Seredenko, M. M.

doi:10.1007/bf01081909

Cited by 2 publications

(3 citation statements)

References 17 publications

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“…The most rostral portions of VLM, which projectionally correspond to the chemosensitive M zone, are known to exert a tonic inhibitory effect on respiratory rhythm generated by SIMSP of early postnatal rats; the neurotransmitter basis of this effect still remains unknown [26]. We suppose that in this case there is certain modulation of glutamatergic synaptic transmission with the involvement of NMDA receptors.…”

Section: Discussionmentioning

confidence: 96%

Involvement of NMDA receptors in the control of respiratory rhythm generated by medullo-spinal preparations of early postnatal rats

et al. 1998

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Effects of a non-competetive blocker of glutamate NMDA receptors, ketamine, on respiratory activity recorded from the phrenic nerve were studied in experiments on superfused in situ semi-isolated medullo-spinal preparations (SIMSP) of 3-to 4-day-old rats. The experiments were carried out under conditions where the ventrolateral medullary region (VLM) was left intact, or its rostral portion (projectionally corresponding to the chemosensitive M zone) was separated by transection. Three-rain-long application of 1.0 pM ketamine evoked a slight increase in the duration of inspiratory discharges (1D) and a statistically significant increase in their frequency. After the rostral VLM had been separated, similar ketamine application resulted in significant increases in the duration, amplitude, and integral intensity of ID and some drop in their frequency. An increase to 10 ,uM ketamine concentration in the superfusing solution determined a significant rise of the ID duration, which Indicates the possibility of inhibition of the mechanisms switching inspiration to expiration. Concurrently, the ID frequency significantly dropped, while their amplitude and integral intensity increased. After separation of the ro~tral VLM, the latter ketamine concentration ceased to increase the ID duration, and their frequency and amplitude significantly dropped. Application of ketamine in the concentration of 100/~M resulted in rather profound decreases of all measured ID parameters, and separation of the rostral VLM exerted no influence on the direction of the above modifications. Thus, we obtained evidence of the involvement of NMDA receptors of the VLM in the control of temporal and frequency-amplitude parameters of respiratory activity of early postnatal rats. Possible localization of NMDA receptors and mechanisms of their involvement in inspiration-expiration switching and tonic inhibitory control of respiratory rhythms are discus~d.

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Section: Discussionmentioning

confidence: 96%

Involvement of NMDA receptors in the control of respiratory rhythm generated by medullo-spinal preparations of early postnatal rats

et al. 1998

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“…In these experimental animals, the most rostral VLM portions, which projectionally correspond to the M chemosensitive zone, are known to tonically inhibit functioning of the bulbar respiratory generator [14], yet neurotransmitter mechanisms of this phenomenon are still unknown. The adaptive importance of such inhibitory control is supposed as follows: it prevents aspiration of amniotic fluid during the birth process and just before this event [17 ].…”

Section: Discussionmentioning

confidence: 99%

“…1, 2). In rats during the first postnatal days, transectioning at this level results in an increase of the ID frequency in the phrenic nerve [14]. It is also known [15 ] that there is a tonic inhibitory glutamatergic mechanism in the rostral VLM part, which modulates respiratory reflexes.…”

Section: Methodsmentioning

confidence: 99%

Involvement of nitric oxide in realization of the NMDA influence on the respiratory rhythm generated by medullo-spinal preparations of early postnatal rats

Volgin

1998

Neurophysiology

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The effects of blocking of NO synthase on the dynamics of NMDA-induced changes in the respiratory activity were studied in experiments on semi-isolated in situ medullo-spinal preparations of 3-lo 4-day-old rats. The experiments were carried out with the ventroiateral regions of the medulla (VLMR) left intact or when the rostral portion of this region (corresponding to the chemce, ensitive zone M) had been separated by a transversial transection. Three-rain-long application of 5.0/aM NMDA increased the frequency of inspiratory discharges (ID); the shifts were more intensive after separation of the VLM rostral portion. Superfusion of preparations with a solution containing 10.0 aM of an NO synthase inhibitor, methyl ester of N6-nitro-L-arginine (MENA), increased the frequency and decreased the amplitude and integral intensity of ID generated by the preparations with the intact VIAl, whereas after separation of the rostral VLM portion this inhibitor decreased the ID frequency. Application of 5 #M NMDA against the background of 10-rain-long superfusion with the 10 pM MENA-containing solution resulted in no significant increase in the ID frequency. Mter the rostral VLM portion had been removed, NMDA application after superfnsion with the MENA-containing solution led to frequency shifts, which did not significantly differ from tho~e in the absence of the blockade of NO synthase. Against the MENA influence, NMDA-induced depression of the ID amplitude became significantly more intensive. The experiments showed that during the early postnatal period endogenous NO is involved in realization of the NMDA influence on the parameters of respiratory activity of rats. Possible mechanisms of the influences exerted by activation of NMDA receptors and by the associated NO synthesis on regulation of the respiratory rhythmogenesis and their specificity within the early postnatal period are discussed.

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Respiratory activity generated by semi-isolated medullo-spinal preparation and recorded from the phrenic nerve of newborn rats

Cited by 2 publications

References 17 publications

Involvement of NMDA receptors in the control of respiratory rhythm generated by medullo-spinal preparations of early postnatal rats

Involvement of NMDA receptors in the control of respiratory rhythm generated by medullo-spinal preparations of early postnatal rats

Involvement of nitric oxide in realization of the NMDA influence on the respiratory rhythm generated by medullo-spinal preparations of early postnatal rats

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