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Control of cardiac rate, contractility, and atrioventricular conduction by medullary raphe neurons in anesthetized rats.
. 2009 Feb; 296(2):H318-24.

Abstract

The sympathetic actions of medullary raphé neurons on heart rate (HR), atrioventricular conduction, ventricular contractility, and rate of relaxation were examined in nine urethane-anesthetized (1-1.5 g/kg iv), artificially ventilated rats that had been adrenalectomized and given atropine methylnitrate (1 mg/kg iv). Mean arterial pressure (MAP), ECG, and left ventricular pressure were recorded. The peak rates of rise and fall in the first derivative of left ventricular (LV) pressure (dP/dtmax and dP/dtmin, respectively) and the stimulus-R ($-R) interval were measured during brief periods of atrial pacing at 8.5 Hz before and after ventral medullary raphé neurons were activated by dl-homocysteic acid (DLH, 0.1 M) or inhibited by GABA (0.3 M) in local microinjections (90 nl). LV dP/dtmax values were corrected for the confounding effect of MAP, determined at the end of the experiments after giving propranolol (1 mg/kg iv) to block sympathetic actions on the heart. DLH microinjections into the ventral medullary raphé region increased HR by 44 +/- 2 beats/min, LV dP/dtmax by 1,055 +/- 156 mmHg/s, and the negative value of LV dP/dtmin by 729 +/- 204 mmHg/s (all, P < 0.001) while shortening the $-R interval by 2.8 +/- 0.8 ms (P < 0.01). GABA microinjections caused no significant change in HR, LV dP/dtmax, or $-R interval but reduced LV dP/dtmin from -5,974 +/- 93 to -5,548 +/- 171 mmHg/s and MAP from 115 +/- 4 to 105 +/- 5 mmHg (both, P < 0.01). Rises in tail skin temperature confirmed that GABA injections effectively inhibited raphé neurons. When activated, the neurons in the ventral medullary raphé region thus enhance atrioventricular conduction, ventricular contractility, and relaxation in parallel with HR, but they provide little or no tonic sympathetic drive to the heart.

Authors+Show Affiliations

Howard Florey Institute, University of Melbourne, Victoria, Australia.No affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Comparative Study
Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

19074673

Citation

Salo, Lauren M., et al. "Control of Cardiac Rate, Contractility, and Atrioventricular Conduction By Medullary Raphe Neurons in Anesthetized Rats." American Journal of Physiology. Heart and Circulatory Physiology, vol. 296, no. 2, 2009, pp. H318-24.
Salo LM, Nalivaiko E, Anderson CR, et al. Control of cardiac rate, contractility, and atrioventricular conduction by medullary raphe neurons in anesthetized rats. Am J Physiol Heart Circ Physiol. 2009;296(2):H318-24.
Salo, L. M., Nalivaiko, E., Anderson, C. R., & McAllen, R. M. (2009). Control of cardiac rate, contractility, and atrioventricular conduction by medullary raphe neurons in anesthetized rats. American Journal of Physiology. Heart and Circulatory Physiology, 296(2), H318-24. https://doi.org/10.1152/ajpheart.00951.2008
Salo LM, et al. Control of Cardiac Rate, Contractility, and Atrioventricular Conduction By Medullary Raphe Neurons in Anesthetized Rats. Am J Physiol Heart Circ Physiol. 2009;296(2):H318-24. PubMed PMID: 19074673.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Control of cardiac rate, contractility, and atrioventricular conduction by medullary raphe neurons in anesthetized rats. AU - Salo,Lauren M, AU - Nalivaiko,Eugene, AU - Anderson,Colin R, AU - McAllen,Robin M, Y1 - 2008/12/12/ PY - 2008/12/17/entrez PY - 2008/12/17/pubmed PY - 2009/3/13/medline SP - H318 EP - 24 JF - American journal of physiology. Heart and circulatory physiology JO - Am. J. Physiol. Heart Circ. Physiol. VL - 296 IS - 2 N2 - The sympathetic actions of medullary raphé neurons on heart rate (HR), atrioventricular conduction, ventricular contractility, and rate of relaxation were examined in nine urethane-anesthetized (1-1.5 g/kg iv), artificially ventilated rats that had been adrenalectomized and given atropine methylnitrate (1 mg/kg iv). Mean arterial pressure (MAP), ECG, and left ventricular pressure were recorded. The peak rates of rise and fall in the first derivative of left ventricular (LV) pressure (dP/dtmax and dP/dtmin, respectively) and the stimulus-R ($-R) interval were measured during brief periods of atrial pacing at 8.5 Hz before and after ventral medullary raphé neurons were activated by dl-homocysteic acid (DLH, 0.1 M) or inhibited by GABA (0.3 M) in local microinjections (90 nl). LV dP/dtmax values were corrected for the confounding effect of MAP, determined at the end of the experiments after giving propranolol (1 mg/kg iv) to block sympathetic actions on the heart. DLH microinjections into the ventral medullary raphé region increased HR by 44 +/- 2 beats/min, LV dP/dtmax by 1,055 +/- 156 mmHg/s, and the negative value of LV dP/dtmin by 729 +/- 204 mmHg/s (all, P < 0.001) while shortening the $-R interval by 2.8 +/- 0.8 ms (P < 0.01). GABA microinjections caused no significant change in HR, LV dP/dtmax, or $-R interval but reduced LV dP/dtmin from -5,974 +/- 93 to -5,548 +/- 171 mmHg/s and MAP from 115 +/- 4 to 105 +/- 5 mmHg (both, P < 0.01). Rises in tail skin temperature confirmed that GABA injections effectively inhibited raphé neurons. When activated, the neurons in the ventral medullary raphé region thus enhance atrioventricular conduction, ventricular contractility, and relaxation in parallel with HR, but they provide little or no tonic sympathetic drive to the heart. SN - 0363-6135 UR - https://www.unboundmedicine.com/medline/citation/19074673/Control_of_cardiac_rate_contractility_and_atrioventricular_conduction_by_medullary_raphe_neurons_in_anesthetized_rats_ L2 - https://journals.physiology.org/doi/10.1152/ajpheart.00951.2008?url_ver=Z39.88-2003&amp;rfr_id=ori:rid:crossref.org&amp;rfr_dat=cr_pub=pubmed DB - PRIME DP - Unbound Medicine ER -