Nicotine shown to have half the constrictive properties on veins as alcohol, and marijuana actually will make them bigger (with vasorelaxatory properties identified in THC)!

Nicotine and vein constriction:

"Smoking was associated with significant changes in the aortic pressure-diameter relation that denote deterioration of the elastic properties and were maintained during the whole study period: the slope of the pressure-diameter loop became steeper (baseline, 35.43±1.38; minute 1, 45.26±1.65; peak at minute 10, 46.36±1.69 mm Hg/mm; P<.001) and aortic distensibility decreased (baseline, 2.08±0.12; minute 1, 1.60±0.08; nadir at minute 5, 1.54±0.07×10⁻⁶ cm²·dyne⁻¹; P<.001). In contrast, no changes in aortic elasticity indexes were observed with sham smoking."

http://circ.ahajournals.org/content/95/1/31.short

Alcohol and vein constriction:

"Blood ethanol levels achieved at 60, 120, and 180 minutes were 649+-48, 1,285±81, and 2,546+-130jug/ml, respectively. LAD cross-sectional area was reduced significantly from control at the end of each of the three dosing periods (-24± 5%, -40± 3%, and -53±.3%; p<0.004). a-Adrenergic blockade had no effecton LAD cross-sectional area, while nicardipine partially reversed the ethanol-induced vasoconstriction. No significant change in vessel cross-sectional area took place in control dogs."

 http://circ.ahajournals.org/content/78/1/165.full.pdf

Marijuana and vein relaxation:

"The present results provide strong evidence that THC is a PPARγ ligand, stimulation of which causes time-dependent vasorelaxation"
This results in a lower blood pressure and better athletic performance.

http://www.sciencedirect.com/science/article/pii/S0006291X05021352