Research paperIdentification and characterization of two functionally distinct groups of spinal cord-projecting paraventricular nucleus neurons with sympathetic-related activity
Section snippets
General procedures
Experiments were performed in male Sprague–Dawley rats (Charles River Laboratories, Wilmington, MA, USA) weighing 350–500 g. Rats were anesthetized by i.p. injection of urethane (800 mg/kg) and α-chloralose (80 mg/kg) (Sigma, St. Louis, MO, USA). Catheters were placed in a femoral artery and vein to measure arterial pressure and to administer drugs, respectively. Following tracheal cannulation, rats were artificially ventilated with oxygen-enriched room air and paralyzed with gallamine
Identification of PVN spinal neurons
Experiments were performed in 41 male Sprague–Dawley rats. Antidromic activity was evoked by spinal cord stimulation in a total of 53 neurons without apparent influence from orthodromic inputs. Of these, 25 were identified by stimulating spinal segments T1–3 and 28 by stimulation at segments T10–12. To avoid mechanical instability and to prolong the viability of each surgical preparation, no attempt was made here to determine if individual neurons could be antidromically identified from both
Discussion
The present data demonstrate for the first time that two functionally distinct groups of neurons are present within the PVN spinal pathway of the rat. Ongoing discharge among cells in both groups was correlated with renal SNA, suggesting that both may subserve sympathetic–regulatory functions. A possible role for Group I neurons in cardiovascular control appears consistent with data showing that their discharge is arterial pulse rhythmic and sensitive to changes in arterial pressure. The lack
Acknowledgements
The authors thank Matthew Cato for excellent technical assistance and Drs. L. C. Daws, S. D. Stocker and J. R. Haywood for constructive comments on the manuscript. This research was supported by National Heart, Lung, and Blood Institute grants HL-56834 and was conducted during the tenure of an American Heart Association Established Investigator Award (G. M. Toney).
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