The phrenic nucleus of the albino rat: A correlative HRP and Golgi study

Abstract

The phrenic nucleus of the adult albino rat was studied by utilizing the O-dianisidine method for the retrograde transport of horseradish peroxidase in conjunction with the zinc chromate modification of the Golgi technique. Application of HRP to the transected phrenic nerve in the neck labeled a column of phrenic motor neurons from C3 to C5 in the ipsilateral spinal cord. However, when HRP was applied to the phrenic nerve intrathoracically, labeled neurons were found from C3 to C6. The long axis of the column of phrenic neurons was oriented tangentially from rostral to caudal poles. There was a gradual shift of the column from posterior to anterior and from lateral to medial positions in the ventral horn. The peroxidase material was also used to localize impregnated phrenic motor neurons in the Golgi sections and to provide quantitative data on phrenic motor neurons. In Golgi-impregnated material two types of phrenic neurons were distinguished on the basis of dendritic morphology and orientation. These neurons were designated (1) large neurons with smooth, radially oriented dendrites, and (2) smaller neurons with varicose, tangentially oriented dendrites. Both types of neurons had a small number of spines and bulbous appendages issuing from the dendritic trunks and branches. The dendritic fields of adjacent phrenic neurons overlapped extensively with one another and with dendrites of more distally placed ventral horn motor neurons. In peroxidase-labeled sagittal sections the dendrites of phrenic neurons were primarily oriented in the rostrocaudal plane. The mean total number of peroxidase-labeled neurons in the phrenic nucleus was 415.75 +/- 18.36 cells. In sagittal sections the mean long axis diameter of phrenic cell bodies was 34.5 micrometers. In frontal sections the mean long axis diameter of phrenic cell bodies was 22.5 micrometers. Thus, from direct measurement, the phrenic neurons were 34% longer in the sagittal plane than in the frontal plane. In the present study each phrenic nucleus contributed fibers only to the ipsilateral phrenic nerve, and no evidence for peripheral crossing of fibers was found.

Okadaic Acid-Sensitive Protein Phosphatases Constrain Phrenic Long-Term Facilitation after Sustained Hypoxia

“…All images received equivalent adjustments to tone scale, gamma, and sharpness. Putative phrenic motor neurons were determined based on size (Ͼ30 m) and location within the ventral horn (Goshgarian and Rafols, 1981).…”

The Therapeutic Effectiveness of Delayed Fetal Spinal Cord Tissue Transplantation on Respiratory Function Following Mid-Cervical Spinal Cord Injury

“…The animal was mechanically ventilated with an oxygen/nitrogen mixture (50% O 2 , balance N 2 ) using a ventilator (volume = 7 ml/kg; frequency = 60-70/min, KDS 35; KD Scientific, Holliston, MA, USA). The partial pressure of end-tidal CO 2 (P ET CO 2 ) was monitored by connecting a CO 2 Capnogard sensor (Novametrix Medical Systems, Madison, WI, USA) to the expiratory line of the ventilator. The P ET CO 2 was maintained at 45 mmHg by adjusting the inspired CO 2 and the ventilator frequency.…”

“…The transverse section with the largest GFPpositive tissue in each animal (n = 31) was selected to quantify the area of uninjured side host tissue, injured side spared host tissue, and GFP-positive tissue using ImageJ software (National Institutes of Health, Bethesda, MD, USA). The data were expressed as the absolute value (i.e., mm 2 ) and a percentage of the uninjured side host tissue.…”

“…Inspiration is generated by contraction of the diaphragm, the primary inspiratory muscle, which is innervated by the phrenic nucleus located at the third to sixth segments of the cervical spinal cord [1,2]. Phrenic motoneurons receive inspiratory impulses from the rostral ventral respiratory group in the brainstem [3][4][5]; therefore, mid-cervical spinal cord injury (SCI) would interrupt this bulbospinal respiratory pathway and directly compromise the phrenic motoneurons.…”

Excitatory amino acid‐mediated chemoreflex excitation of respiratory neurones in rostral ventrolateral medulla in rats.

“…In this study, we have therefore investigated whether the RVL respiratory neurones mediate the expression of the respiratory chemoreflex; whether they, like the local vasomotor neurones, are excited by glutamatergic inputs during the chemoreflexes; and whether they might be a major medullary respiratory centre, directly and/or indirectly affecting activities of the diaphragmatic motoneurones of the phrenic motor nucleus in the C4-C5 segments of the cervical spinal cord (Goshgarian & Rafols, 1981 …”