Effects of intrathecal administration of adrenergic agonists on the frequency of copulatory pelvic thrusting of the male rat

The effects of the intrathecal perispinal administration of adregergic agonists on the characteristic of frequency, duration, and vigor of pelvic thrusting displayed by male rats during copulation was assessed by an accelerometric technique. A different dose of one drug (noradrenaline, clonidine or isoproterenol) and saline as control was administered at the lumbosacral level of the spinal cord to sexually active male rats in tests of sexual behavior performed at weekly intervals. The intrathecal administration of noradrenaline (alpha-adrenoceptor agonist) increased the frequency of pelvic thrusting in mount and intromission responses, whereas both the alpha2-adrenoceptor agonist clinidine (25 µg) and the ß-adrenoceptor agonist isoproterenol ( 40 µg) reduced the frequency of pelvic thrusting in these responses as compared to values obtained under the intrathecal administration of saline. On the other hand, the duration of the thrusting trains and the potency or vigor of pelvic thrusting in mounts and intromissions did not differ from values obtained under saline treatment. These findings indicate a possible participation of noradrenaline in the modulation of the spinal mechanisms involved in the generation of rhytmic pelvic thrustint performed by the male rat during copulation