Korean J Anesthesiol.  2004 Feb;46(2):225-231. 10.4097/kjae.2004.46.2.225.

Effects of Bupivacaine on Strips of Rat Thoracic Aortic Rings

• Lee DM
• Yoon SH
• Lee JU

• KMID: 2039725
• DOI: http://doi.org/10.4097/kjae.2004.46.2.225

Abstract

BACKGROUND
Local anesthetics depress smooth muscle contractions in the intact bowel and in strips of isolated intestine, and also relax bronchial smooth muscle. Following systemic absorption, local anesthetics act on the cardiovascular system. Their primary site of action is the myocardium, where decreases in electrical excitability, conduction rates, and contraction force occur. In addition, most local anesthetics cause arteriolar dilation.
METHODS
The ability of bupivacaine to elicit a direct relaxant effect on vascular smooth muscle was studied using isolated rat thoracic aortic rings contracted by phenylephrine (PE). Each thoracic aorta ring was suspended on wire supports in a 20 ml tissue bath under 2 g of resting tension. All tissues were bathed in Tris Tyrode solution at 37 degrees C and 100% oxygen was supplied.
RESULTS
1. Bupivacaine (10(-5) M) inhibited PE induced contractions of aortic rings significantly (P < 0.05). 2. Relaxation of aortic rings by bupivacaine (10(-5) M) was reversed by L-NAME pretreatment. 3. Relaxation of aortic rings by bupivacaine (10(-5) M) was not recovered by methylene blue. 4. Indomethacine enhanced the contraction of aortic rings by bupivacaine (10(-5) M). 5. Bupivacaine (10(-5) M) inhibited both the influx of extracellular Ca+2 and intracellular Ca+2 release. 6. Relaxation of aortic rings by bupivacaine 10(-5) M was recovered by tetraethylammonium.
CONCLUSIONS
From the results obtained, it is concluded that the relaxation effects of bupivacaine are related with endothelium dependent, and that cyclooxygenase and not guanylate cyclase participates in this relaxation. Bupivacaine inhibited both intracellular calcium release and extracelluar calcium influx. In addition, the potassium channel was also found to be related to this relaxation effect.

Keyword

bupivacaine; smooth muscle; phenylephrine; rat

MeSH Terms

Absorption
Anesthetics, Local
Animals
Aorta, Thoracic
Baths
Bupivacaine*
Calcium
Cardiovascular System
Endothelium
Guanylate Cyclase
Indomethacin
Intestines
Methylene Blue
Muscle, Smooth
Muscle, Smooth, Vascular
Myocardium
NG-Nitroarginine Methyl Ester
Oxygen
Phenylephrine
Potassium Channels
Prostaglandin-Endoperoxide Synthases
Rats*
Relaxation
Tetraethylammonium
Anesthetics, Local
Bupivacaine
Calcium
Guanylate Cyclase
Indomethacin
Methylene Blue
NG-Nitroarginine Methyl Ester
Oxygen
Phenylephrine
Potassium Channels
Prostaglandin-Endoperoxide Synthases
Tetraethylammonium