Ca2+/calmodulin system: Participation in the progesterone-induced facilitation of lordosis behavior in the ovariectomized estrogen-primed rat

We studied the effect some drugs that participate in the Ca2+/calmodulin system have on the progesterone (P) facilitation of lordosis behavior in ovariectomized estradiol (E(2)) primed rats. We injected rats 44 h after E(2) priming with 2 mg P together with various dosages of one of the following compounds: pentobarbital, trifluoperazine (TPZ), promethazine (PMZ), Chlorpromarine (CPZ), haloperidol (HAL), pimozide (PIM), and verapamil (VER). Then 4 h after treatment, animals were tested for sexual behavior, expressed as the lordosis quotient (LQ). All drugs at 4 mg/kg or higher inhibited lordosis, but only HAL, PIM, and VER were active at 1 mg/kg. The maximum level of activity was shown by PIM, although al the dose of 8 mg/kg no statistical differences were found between this compound and TPZ or HAL. Pentobarbital (25 mg/kg) showed no significant difference from saline-treated controls. The activity of the tested drugs on the facilitation of sexual behavior appears to be related to their efficiency as inhibitors of calmodulin (CaM)-dependent phosphodiesterase and as ligands for the Ca2+-CaM complex.