Progesterone Enhancement of Lysergic Acid Diethylamide and Levo-5-Hydroxytryptophan Stimulation of the Copulatory Response in the Female Rat
Anni Sietnieks, Bengt J. Meyerson
Neuroendocrinology March 26, 2008 Peer reviewed DOI: 10.1159/000123499
Summary
The study investigates how different hormone treatments affect the lordosis response (LR) in ovariectomized rats, particularly focusing on the influence of estrogen and progesterone alongside LSD and L-5-HTP. It was found that a dose of LSD (10 μg/kg) increased LR when activated by estradiol benzoate (EB), while lower doses of LSD had no effect without additional hormones. Small doses of L-5-HTP similarly stimulated LR, with progesterone enhancing these effects.
Study at a glance
| Population | ovariectomized rats |
|---|---|
| Key finding | LSD at a dose of 10 μg/kg increased lordosis response when activated by estradiol benzoate, while lower doses were ineffective without additional hormone treatment. |
Abstract
Copulatory behavior in the ovariectomized rat, i.e. the lordosis response (LR) on being mounted by a male, can be induced by administration of either estrogen alone or estrogen followed by progesterone. LR has been shown to be inhibited by lysergic acid diethylamide (LSD) in certain doses (≥50 μg/kg) and by Levo-5-hydroxytryptophan (L-5-HTP) (≥2.5 mg/kg). This effect was recently found to be enhanced by increasing doses of progesterone. In contrast, small doses of LSD (5–30 μg/kg) have been shown to increase LR activated by estrogen alone. The effects of various hormone treatments on the stimulatory action of LSD were tested in the present study. When the lordosis behavior was activated by estradiol benzoate (EB) alone (25 or 7 × 2 μg/kg), LR increased 10 min after injection of LSD in a dose of 10 μg/kg. There were no detectable effects in animals treated with estrogen alone when the dose of LSD was lowered to 1 μg/kg. LSD in the latter dose gave an increased response, however, when LR was activated by EB (5 μg/kg) in combination with progesterone (4.0 mg/rat). An analogous study was conducted with L-5-HTP, after pretreatment with pargyline and R04–4602. Small doses of L-5-HTP (0.25 and 0.05 mg/kg) stimulated the LR and the influence of progesterone was the same as for small doses of LSD. Possible mechanisms underlying the observed influence of progesterone on serotonergic mechanisms involved in the lordosis behavior are discussed.