Table 2

Potency of RTX relative to capsaicin in selected assays in the rat

AssayRelative Potency
In vitro experiments
 Inhibition of [3H]RTX binding to DRG neurons (1)100,000
 Induction of 45Ca2+ uptake by DRG neurons (1)300
 Activation of single channels in patch-clamped DRG neurons (2)500
 Evoking currents via cloned VR1 expressed in oocytes (3)20
 Twitch inhibition in vas deferens (4)10,000
 Desensitization of urinary bladder to subsequent challange (4)1,000
 Induction of cGMP in DRG neurons (5)660
 Contractions of isolated urinary bladder (4)1
In vivo experiments
 Inhibition of xylene-induced Evans’ blue extravasation (6)20,000
 Induction of hypothermia (6)7,000
 Pungency (eye-wipings) (6)10
 Activation of pulmonary chemoreflex (7, 8)RTX inactive
 Desensitization of pulmonary chemoreflex (7)Capsaicin inactive
  • References indicated in parentheses: (1) Ács et al., 1996b; (2) Oh et al., 1996; (3) Caterina et al., 1997; (4) Maggi et al., 1990; (5) Winter et al., 1990; (6) Szallasi and Blumberg, 1989a; (7)Szolcsányi et al., 1990; and (8) Szolcsányi et al., 1991.