TY - JOUR
T1 - Barosensitive neurons in the rostral ventrolateral medulla of the rat in vivo
T2 - Morphological properties and relationship to C1 adrenergic neurons
AU - Lipski, J.
AU - Kanjhan, R.
AU - Kruszewska, B.
AU - Smith, M.
N1 - Funding Information:
Acknowledgements This study was supported by grants from the New Zealand Health Research Council and the New Zealand Lottery Grants Board. We thank Lisa Christmas for secretarial assistance.
PY - 1995/11
Y1 - 1995/11
N2 - The aim of this study, conducted in anaesthetized rats, was to examine the morphology of barosensitive neurons in the rostral ventrolateral medulla and their immunoreactivity for a catecholamine synthesizing enzyme, tyrosine hydroxylase. Thirty neurons displaying inhibitory postsynyptic potentials following stimulation of the aortic depressor nerve were intracellularly labelled with Lucifer Yellow or Neurobiotin. Some of these neurons could be excited antidromically from the second thoracic segment of the spinal cord, with conduction velocities of spinal axons ranging from 1.9 to 7.2 m/s. The filled somas were found immediately caudal to the facial nucleus and ventral or ventromedial to compact formation of the nucleus ambiguus. Some dendrites reached the ventral medullary surface. Axons usually projected dorsomedially and then made a sharp rostral and/or caudal turn. The caudally projecting axon could, in some cases, be followed to the first cervical segment of the spinal cord. Seven cells issued fine axon collaterals on the ipsilateral side. These were identified mainly in two areas: in the rostral ventrolateral medulla (or immediately dorsomedial to that region), and within the dorsal vagal complex. Seven of 27 examined cells (26%) were tyrosine hydroxylase-immunoreactivee and were classified as C1 adrenergic neurons. No clear relationship was found between the presence or absence of adrenergic phenotype and the morphology of filled cells. However, the amplitude of aortic nerve-evoked inhibitory postsynaptic potentials was significantly larger in tyrosine hydroxylase-positive neurons. Possible reasons for the low percentage of barosensitive cells with tyrosine hydroxylase immunoreactivity found in this study, in comparison with previously published estimates, are discussed. This is the first study describing the morphology of neurons in this part of the medulla identified as barosensitive in vivo, and directly demonstrating adrenergic phenotype in a subset of these neurons.
AB - The aim of this study, conducted in anaesthetized rats, was to examine the morphology of barosensitive neurons in the rostral ventrolateral medulla and their immunoreactivity for a catecholamine synthesizing enzyme, tyrosine hydroxylase. Thirty neurons displaying inhibitory postsynyptic potentials following stimulation of the aortic depressor nerve were intracellularly labelled with Lucifer Yellow or Neurobiotin. Some of these neurons could be excited antidromically from the second thoracic segment of the spinal cord, with conduction velocities of spinal axons ranging from 1.9 to 7.2 m/s. The filled somas were found immediately caudal to the facial nucleus and ventral or ventromedial to compact formation of the nucleus ambiguus. Some dendrites reached the ventral medullary surface. Axons usually projected dorsomedially and then made a sharp rostral and/or caudal turn. The caudally projecting axon could, in some cases, be followed to the first cervical segment of the spinal cord. Seven cells issued fine axon collaterals on the ipsilateral side. These were identified mainly in two areas: in the rostral ventrolateral medulla (or immediately dorsomedial to that region), and within the dorsal vagal complex. Seven of 27 examined cells (26%) were tyrosine hydroxylase-immunoreactivee and were classified as C1 adrenergic neurons. No clear relationship was found between the presence or absence of adrenergic phenotype and the morphology of filled cells. However, the amplitude of aortic nerve-evoked inhibitory postsynaptic potentials was significantly larger in tyrosine hydroxylase-positive neurons. Possible reasons for the low percentage of barosensitive cells with tyrosine hydroxylase immunoreactivity found in this study, in comparison with previously published estimates, are discussed. This is the first study describing the morphology of neurons in this part of the medulla identified as barosensitive in vivo, and directly demonstrating adrenergic phenotype in a subset of these neurons.
KW - 3,3′-diaminobenzidine tetrahydrochloride
KW - DAB
KW - EPSP
KW - FITC
KW - IPSP
KW - PNMT
KW - RVLM
KW - TH
KW - central cardiovascular control
KW - excitatory postsynaptic potential
KW - fluorescein isothiocyanate
KW - inhibitory postsynaptic potential
KW - intracellular recording and labelling
KW - phenylethanolamine-N-methyltransferase
KW - presympathetic (sympathoexcitatory) neurons
KW - rostral ventrolateral medulla
KW - tyrosine hydroxylase
UR - http://www.scopus.com/inward/record.url?scp=0028832479&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0028832479&partnerID=8YFLogxK
U2 - 10.1016/0306-4522(95)92652-Z
DO - 10.1016/0306-4522(95)92652-Z
M3 - Article
C2 - 8552253
AN - SCOPUS:0028832479
SN - 0306-4522
VL - 69
SP - 601
EP - 618
JO - Neuroscience
JF - Neuroscience
IS - 2
ER -