Which of these mediate the precapillary sphincter relaxation:

A i.e. Local hormonesPrecapillary sphincters are layer of smooth muscle fibres present just at the point where a metaeriole.There is no innervation on precapillary sphincter.Q- Their dilatation or constriction (to control the blood flow) depends on local hormones.Q , product of metabolism, hydrogen ions etc.Catecholamines causes sphincter constriction.Factors affecting the caliber of aeriole- Decreased local temperature - Autoregulation- Endothelin-1- Platelet serotonin- Thromboxane A2Epinephrin (except in skeletal muscle & liver)- Norepinephrin- AVP- Angiotensin II- Neuropeptide YDilatationIncreased K+, adenosine.- Increased CO2- Decreased 02- Decreased local pH- Decreased local temperature- NO- Prostacyclin- Kinins- Epinephrin in skeletal muscle & liver Q- Substance P Q- Histamine Q- ANP- VIP