Identification of different types of respiratory neurones in the dorsal brainstem nucleus tractus solitarius of the rat.
In Nembutal anaesthetised, spontaneously breathing rats, stereotaxic mapping of the nucleus tractus solitarius (NTS) for respiratory neuronal activity was undertaken. Eight different types of respiratory cells were found between 0.25 and 1.5 mm lateral to midline, extending 0.5 mm caudal to 1.5 mm rostral to obex, and 0.4-1.5 mm below the dorsal surface. A study of the respiratory motor (diaphragm EMG) and neuronal responses to excitatory amino acid (EAA) stimulation of the NTS areas was undertaken. Electrical stimulation of the vagus nerve was employed to study the NTS cellular responses to activation of pulmonary afferents. The effects of chemical activation of the midbrain periaqueductal grey (PAG) on NTS respiratory neuronal activity were investigated. EAA microinjections into the ventrolateral NTS rostral to the obex resulted in an increase in respiratory motor frequency along with increases to inspiratory cell discharge, whilst microinjections into the medial NTS caudal to the obex caused respiratory depression. EAA stimulation of calamus scriptorius produced apnea. NTS inspiratory neurones were inhibited following stimulation of ipsilateral vagus nerve, suggesting their involvement in the Hering-Breuer reflex pathway. PAG stimulation caused excitation of the NTS inspiratory cells indicating the presence of an excitatory respiratory pathway between the two nuclei. Following beta-adrenergic antagonist pre-treatment of ventrolateral NTS, EAA microinjections into PAG did not evoke a cardiorespiratory effect. Based on the various findings the role of NTS in organising respiration in the rat is discussed.
Subramanian
Hari H
HH
School of Biomedical Sciences, Faculty of Health Sciences, University of Sydney, East Street, PO Box 170 Lidcombe, NSW 1825, Australia. Hari.Subramanian@ki.se
Chow
Chin Moi
CM
Balnave
Ron J
RJ
D000200:Action Potentials / Q000187:drug effects; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D001931:Brain Mapping; D004558:Electric Stimulation / Q000379:methods; D004576:Electromyography / Q000379:methods; D018846:Excitatory Amino Acids / Q000494:pharmacology; D005260:Female; D008297:Male; D009474:Neurons / Q000145:classification* / Q000187:drug effects / Q000502:physiology*; D011433:Propranolol / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012119:Respiration / Q000187:drug effects; D017552:Solitary Nucleus / Q000166:cytology*; D014630:Vagus Nerve / Q000502:physiology / Q000528:radiation effects
D000319:Adrenergic beta-Antagonists; D018846:Excitatory Amino Acids; D011433:Propranolol