“There was, however, an enhanced … the NA sensitivity with cocaine (an inhibitor of the …) in vessels from the hypertensives [pD2(+cocaine) and pD2(-cocaine) were 0.185 +/- 0.53) and 0.040 +/- 0.044, …, respectively, p less than 0.05] suggesting an abnormality of presynaptic function in essential hypertension.”