Postjunctional alpha 2-adrenoceptors mediate vasoconstriction in human subcutaneous resistance vessels

Area of Science:

• Pharmacology
• Vascular Biology
• Adrenoceptor Research

Background:

• Alpha 2-adrenoceptors play a role in regulating vascular tone.
• Previous research has not clearly defined the presence and function of alpha 2-adrenoceptors in human resistance arteries.

Purpose of the Study:

• To investigate the presence and function of postjunctional alpha 2-adrenoceptors in human subcutaneous resistance arteries.
• To compare the response of resistance arteries with medium-sized muscular arteries to alpha 2-agonists.

Main Methods:

• In vitro organ bath studies on human medium-sized muscular arteries (1-4 mm internal diameter).
• Microvascular myography on human subcutaneous resistance arteries (103-626 microns internal diameter).
• Concentration-response curves were generated for alpha 2-agonists (B-HT 933, UK 14304) and antagonist (yohimbine).

Main Results:

• Medium-sized muscular arteries showed no response to alpha 2-agonists.
• Subcutaneous resistance arteries exhibited concentration-dependent contractions to B-HT 933 (pD2 = 5.11 ± 0.09).
• Yohimbine (alpha 2-antagonist) shifted the B-HT 933 curve rightward (pA2 = 7.86 ± 0.12), confirming receptor interaction.
• A negative correlation was observed between vessel calibre and maximal response to B-HT 933.

Conclusions:

• Human subcutaneous resistance arteries possess functional postjunctional alpha 2-adrenoceptors.
• These receptors are absent or non-functional in medium-sized human muscular arteries.
• The findings highlight regional differences in alpha 2-adrenoceptor distribution and function within the human vasculature.