**TxA2 antagonists**

TxA2 is one of the the most potent vasoconstrictors known and it is very potent in IMA as well [10,13]. Inasmuch as its importance in thrombosis together with its elevated plas‐ ma concentrations during cardiopulmonary bypass, specific TxA2 antagonists may be use‐ ful in the antispastic therapy of IMA. Accordingly, specific TxA2 antagonist GR30191 is a potent vasodilator for TxA2-mediated contraction in IMA [86]. However, to date, no clini‐ cal data are available.

#### **5-HT receptor antagonists**

Studies on human IMA have shown that 5-HT directly contracts IMA through 5-HT1D and 5-HT2 receptors [33,108-110]. In IMA, 5-HT receptor mediated contractions are un‐ masked when endothelium is denuded [13,42]. Additionally, studies have shown 5-HT may interact synergistically with other vasoconstrictor substances, such as TxA2 released from platelets during thrombus formation, and 5-HT receptor mediated contractions may be unmasked or amplified [33,108-110]. 5-HT2A receptor antagonist ketanserin has antihy‐ pertensive properties and it's recently used to reduce the severity and frequency of the vasospasm in Raynaud's phenomenon [111]. Therefore, it may have potential to over‐ come IMA spasm when it's applied topically.

#### **Testosterone**

Testosterone may exert vasorelaxant effects on several vascular tissues [112-119]. We have studied effects of testosterone in the human IMA and found that vasorelaxant re‐ sponse to testosterone may occur in via large-conductance Ca2+-activated K+ channelopening action [112]. Clinical studies of testosterone therapy in male patients with coronary artery disease raised promising results. Therefore, the use of testosterone, i.e. direct topical administration on adventitia, as a vasorelaxant agent may be considered for antispastic therapy in arterial grafts.

#### **Iloprost and botilinum toxin**

It has been demonstrated that botilinum toxin may prevent arterial spasm in vitro [120]. Iloprost, a PGI2 analogue, may be considered as an alternative antispastic agent in arteri‐ al grafts [121].
