scholarly journals Monosynaptic inhibition of phrenic motoneurons: a long descending projection from Botzinger neurons

1984 ◽  
Vol 4 (9) ◽  
pp. 2350-2353 ◽  
Author(s):  
EG Merrill ◽  
L Fedorko
Keyword(s):  
Phrenic Motoneurons ◽  
Monosynaptic Inhibition

Some effects of superior laryngeal nerve stimulation on sympathetic preganglionic neuron firing

1979 ◽  
Vol 57 (10) ◽  
pp. 1073-1081 ◽  
Author(s):  
Urs Gerber ◽  
Canio Polosa
Keyword(s):  
Firing Pattern ◽  
Superior Laryngeal Nerve ◽  
Inhibitory Effect ◽  
Laryngeal Nerve ◽  
Depressant Effect ◽  
Excitatory Effect ◽  
Sympathetic Preganglionic Neurons ◽  
Preganglionic Neurons ◽  
Phrenic Motoneurons ◽  
Frequency Of Stimulation

Repetitive electrical stimulation of afferent fibers in the superior laryngeal nerve (SLN) evoked depressant or excitatory effects on sympathetic preganglionic neurons of the cervical trunk in Nembutal-anesthetized, paralyzed, artificially ventilated cats. The depressant effect, which consisted of suppression of the inspiration-synchronous discharge of units with such firing pattern, was obtained at low strength and frequency of stimulation (e.g. 600 mV, 30 Hz) and was absent at end-tidal CO2 values below threshold for phrenic nerve activity. The excitatory effect required higher intensity and frequency of stimulation and was CO2 independent. The depressant effect on sympathetic preganglionic neurons with inspiratory firing pattern seemed a replica of the inspiration-inhibitory effect observed on phrenic motoneurons. Hence, it could be attributed to the known inhibition by the SLN of central inspiratory activity, if it is assumed that this is a common driver for phrenic motoneurons and some sympathetic preganglionic neurons. The excitatory effect, on the other hand, appears to be due to connections of SLN afferents with sympathetic preganglionic neurons, independent of the respiratory center.

Phrenic afferents and ventilatory control at increased end-expiratory lung volumes in cats

1989 ◽  
Vol 66 (3) ◽  
pp. 1297-1303 ◽  
Author(s):  
S. Iscoe
Keyword(s):  
Steady State ◽  
Independent Effect ◽  
Respiratory Drive ◽  
Phrenic Motoneurons ◽  
Partial Pressure Of Co2 ◽  
Before And After ◽  
Steady State Responses ◽  
Spontaneously Breathing ◽  
State Responses

The role of phrenic afferents in controlling inspiratory duration (TI) at elevated end-expiratory lung volume (EEV) has been studied in pentobarbital-anesthetized, spontaneously breathing cats with intact vagi. Responses to increases in EEV, induced by imposition of an expiratory threshold load (ETL) of 10 cmH2O, were monitored before and after section of cervical dorsal roots C3-C7. The immediate (first-breath) effect of application of ETL was a prolongation of both TI and expiratory duration (TE). After 10 min of breathing against the ETL, average TI returned to control values but TE remained prolonged. Abolishing feedback from the diaphragm did not affect these responses. When steady-state responses to ETL were compared with those elicited by inhalation of 5–6% CO2 in O2, changes in EEV had, on average, no independent effect on respiratory drive (rate of rise of integrated phrenic activity), although phrenic activity increased greatly in some cats despite little or no change in arterial partial pressure of CO2. These data indicate that diaphragmatic receptors do not contribute to either the immediate (first-breath) or steady-state responses of phrenic motoneurons to increases in EEV in intact cats.

Phrenic and external intercostal motoneuron activity during progressive asphyxia

1987 ◽  
Vol 63 (4) ◽  
pp. 1413-1420 ◽  
Author(s):  
G. Macefield ◽  
B. Nail
Keyword(s):  
Duty Cycle ◽  
Instantaneous Frequency ◽  
Phrenic Nerve ◽  
Artificial Ventilation ◽  
Phrenic Motoneurons ◽  
Inspiratory Activity ◽  
Motoneuron Activity ◽  
Intercostal Nerves

Phrenic and external intercostal motoneuron activities were compared during progressive asphyxia induced by the interruption of artificial ventilation in the pentobarbital-urethan-anesthetized, gallamine-paralysed rabbit. The relative augmentation of inspiratory activity of the T1-T4 external intercostal nerves was significantly greater than that of the phrenic nerve during asphyxic hyperpnea. This was associated with a greater recruitment of intercostal than of phrenic motoneurons, particularly late in the hyperpneic phase immediately before the period of asphyxic apnea. However, peak and average discharge frequencies developed by intercostal motoneurons (n = 20) were only approximately 60% of those of the phrenic motoneurons (n = 28). Gasping respiration terminated the apneic period and was associated with a further intense recruitment of intercostal though not of phrenic motoneurons, but discharge frequencies developed by the intercostal motoneurons remained approximately 60% of those of the phrenic motoneurons. The instantaneous frequency profiles generated by the motoneurons often exhibited progressive changes during the terminal stages of hyperpnea (reduction in inspiratory duration and duty cycle and increases in inspiratory slope and discharge frequencies) such that much of the character of gasping respiration became evident before the apnea. Such smooth transitional sequences do not obviate the existence of an “independent gasping center” but do require that such a proposed center at least possess the capacity for interaction with those sites responsible for the generation of eupneic and hyperpneic respiration.

Excitatory connections between upper cervical inspiratory neurons and phrenic motoneurons in cats

1994 ◽  
Vol 77 (2) ◽  
pp. 679-683 ◽  
Author(s):  
Y. Nakazono ◽  
M. Aoki
Keyword(s):  
Phrenic Nerve ◽  
Respiratory Neurons ◽  
Transmission Delays ◽  
Phrenic Motoneurons ◽  
Inspiratory Neurons ◽  
Upper Cervical ◽  
Cervical Segment ◽  
Focal Cooling ◽  
Descending Influences ◽  
Phrenic Motoneuron

This study aimed to determine whether upper cervical inspiratory neurons (UCINs), which are localized in the intermediolateral part of the gray matter of the upper cervical segments, have propriospinal connections to phrenic motoneurons of the ipsilateral lower cervical segment in anesthetized cats. Unit action potentials of UCINs were extracellularly recorded simultaneously with ipsilateral phrenic nerve activity. To eliminate the descending influences from medullary respiratory neurons to phrenic motoneurons, bulbospinal conduction paths were temporarily blocked by focal cooling applied to the ventral caudal medulla at the pyramidal decussation level by means of a cooling thermode (1 mm tip diam). By using a spike-triggered method, during cooling phrenic nerve activities were evoked by UCIN spikes that were elicited by microinjection of L-glutamate for 20 of the 55 (36%) UCIN units examined. The onset latencies of these phrenic motoneuron responses ranged from 1.5 to 7.1 ms (mean 3.6 ms), depending on synaptic transmission delays. These results clearly demonstrate that UCINs have, at least in part, excitatory mono- and paucisynaptic connections with ipsilateral phrenic motoneurons.

Neural Organization of the Pathways From the Superior Colliculus to Trochlear Motoneurons

2007 ◽  
Vol 97 (5) ◽  
pp. 3696-3712 ◽  
Author(s):  
Yoshiko Izawa ◽  
Yuriko Sugiuchi ◽  
Yoshikazu Shinoda
Keyword(s):  
Superior Colliculus ◽  
Interstitial Nucleus Of Cajal ◽  
Saccadic System ◽  
Neural Organization ◽  
Premotor Neurons ◽  
Monosynaptic Inhibition ◽  
Disynaptic Inhibition ◽  
Forel's Field H ◽  
Stimulation Of ◽  
Monosynaptic Excitation

The neural organization of the pathways from the superior colliculus (SC) to trochlear motoneurons was analyzed in anesthetized cats using intracellular recording and transneuronal labeling techniques. Stimulation of the ipsilateral or contralateral SC evoked excitation and inhibition in trochlear motoneurons with latencies of 1.1–2.3 and 1.1–3.8 ms, respectively, suggesting that the earliest components of excitation and inhibition were disynaptic. A midline section between the two SCs revealed that ipsi- and contralateral SC stimulation evoked disynaptic excitation and inhibition in trochlear motoneurons, respectively. Premotor neurons labeled transneuronally after application of wheat germ agglutinin-conjugated horseradish peroxidase into the trochlear nerve were mainly distributed ipsilaterally in the Forel's field H (FFH) and bilaterally in the interstitial nucleus of Cajal (INC). Consequently, we investigated these two likely intermediaries between the SC and trochlear nucleus electrophysiologically. Stimulation of the FFH evoked ipsilateral mono- and disynaptic excitation and contralateral disynaptic inhibition in trochlear motoneurons. Preconditioning stimulation of the ipsilateral SC facilitated FFH-evoked monosynaptic excitation. Stimulation of the INC evoked ipsilateral monosynaptic excitation and inhibition, and contralateral monosynaptic inhibition in trochlear motoneurons. Preconditioning stimulation of the contralateral SC facilitated contralateral INC-evoked monosynaptic inhibition. These results revealed a reciprocal input pattern from the SCs to vertical ocular motoneurons in the saccadic system; trochlear motoneurons received disynaptic excitation from the ipsilateral SC via ipsilateral FFH neurons and disynaptic inhibition from the contralateral SC via contralateral INC neurons. These inhibitory INC neurons were considered to be a counterpart of inhibitory burst neurons in the horizontal saccadic system.

Physiological Characterization of Synaptic Inputs to Inhibitory Burst Neurons From the Rostral and Caudal Superior Colliculus

2005 ◽  
Vol 93 (2) ◽  
pp. 697-712 ◽  
Author(s):  
Y. Sugiuchi ◽  
Y. Izawa ◽  
M. Takahashi ◽  
J. Na ◽  
Y. Shinoda
Keyword(s):  
Superior Colliculus ◽  
Abducens Nucleus ◽  
Antidromic Activation ◽  
Synaptic Inputs ◽  
Burst Neurons ◽  
Physiological Characterization ◽  
Monosynaptic Inhibition ◽  
Disynaptic Inhibition ◽  
Stimulation Of

The caudal superior colliculus (SC) contains movement neurons that fire during saccades and the rostral SC contains fixation neurons that fire during visual fixation, suggesting potentially different functions for these 2 regions. To study whether these areas might have different projections, we characterized synaptic inputs from the rostral and caudal SC to inhibitory burst neurons (IBNs) in anesthetized cats. We recorded intracellular potentials from neurons in the IBN region and identified them as IBNs based on their antidromic activation from the contralateral abducens nucleus and short-latency excitation from the contralateral caudal SC and/or single-cell morphology. IBNs received disynaptic inhibition from the ipsilateral caudal SC and disynaptic inhibition from the rostral SC on both sides. Stimulation of the contralateral IBN region evoked monosynaptic inhibition in IBNs, which was enhanced by preconditioning stimulation of the ipsilateral caudal SC. A midline section between the IBN regions eliminated inhibition from the ipsilateral caudal SC, but inhibition from the rostral SC remained unaffected, indicating that the latter inhibition was mediated by inhibitory interneurons other than IBNs. A transverse section of the brain stem rostral to the pause neuron (PN) region eliminated inhibition from the rostral SC, suggesting that this inhibition is mediated by PNs. These results indicate that the most rostral SC inhibits bilateral IBNs, most likely via PNs, and the more caudal SC exerts monosynaptic excitation on contralateral IBNs and antagonistic inhibition on ipsilateral IBNs via contralateral IBNs. The most rostral SC may play roles in maintaining fixation by inhibition of burst neurons and facilitating saccadic initiation by releasing their inhibition.

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