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This Article Full Text Full Text (PDF) All Versions of this Article: 89/3/303    most recent expphysiol.2004.027201v1 Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Fellet, A. L. Articles by Balaszczuk, A. M. Search for Related Content PubMed PubMed Citation Articles by Fellet, A. L. Articles by Balaszczuk, A. M. Related Collections Cardiovascular control

Department of Physiology, School of Pharmacy and Biochemistry, University of Buenos Aires, IQUIMEFA-CONICET, Argentina.

We have previously reported that acute administration of N^G-nitro-L-arginine methyl ester (L-NAME) increases the mean arterial pressure (MAP) and heart rate (HR) in autonomic-blocked (CAB) anaesthetized rats. In the present study we examined whether thyroid and adrenal glands are involved in these pressor and chronotropic responses. Sprague-Dawley rats were studied after bilateral vagotomy and ganglionic blockade with hexamethonium (10 mg kg^–1), and stabilization of MAP with infusion of phenylephrine (PE) (6 µg kg^–1 min^–1). The rats were divided into groups: L, CAB; PE, CAB + PE bolus (6 µg kg^–1); L-TX, thyroidectomy + CAB; L-AX, adrenalectomy + CAB; TX, only thyroidectomy; C, CAB. L, L-AX and L-TX groups received a bolus of L-NAME (7.5 mg kg^–1). Triiodothyronine (T3), thyroxin (T4) and thyrotropin (TSH) levels were measured in L and L-TX rats before and after L-NAME administration. Reduced nicotamide adenine dinucleotide (NADPH) diaphorase activity was determined in heart and aorta of the TX group. The pressor response induced by L-NAME was similar in all groups. L-NAME-induced-tachycardia was associated with this rise in MAP. Adrenalectomy did not modify this chronotropic response, but it was attenuated by thyroidectomy. Thyroidectomy by itself decreased the circulating levels of T3 but it had no effect on the plasma levels of T4 and TSH. L and L-TX groups showed similar levels of circulating T4 and TSH, meanwhile the plasma level of T3 decreased in the L group. Nitric oxide synthase (NOS) activity in atria as well as in aorta was greater in the TX group compared with C. When autonomic influences are removed, the thyroid gland modulates intrinsic heart rate via a mechanism that involves, at least in part, the nitric oxide pathway.

(Received 15 January 2004; accepted after revision 26 February 2004; first published online 16 March 2004)
Corresponding author A. L. Fellet Department of Physiology, school of Pharmacy and Biochemistry, University of Buenos Aires, (1113) Jun'n 956, 7° Piso Buenos Aires, Argentina. Email: afellet{at}huemul.ffyb.uba.ar

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