Prevention of progesterone-induced lordosis behavior by alpha or beta adrenergic antagonists in ovariectomized...

The effect of systemic administration of adrenergic alpha (phenoxybenzamine and prazosin) and beta (propranolol) antagonists on the lordosis behavior induced by progesterone (2.0 mg/rat) was studied in ovariectomized estradiol benzoate (4.0 micrograms/rat) primed rats. The effect of these antagonists was also tested on the lordosis behavior induced in ovariectomized rats by estradiol benzoate alone (1.25 micrograms/rat each two days). Phenoxybenzamine (0.8, 4.0 and 20.0 mg/kg), propranolol (0.8, 4.0 and 20.0 mg/kg) and prazosin (0.2 and 1.0 mg/kg) caused a dose-dependent reduction of progesterone induced lordosis. By contrast, phenoxybenzamine (4.0 mg/kg), propranolol (4.0 mg/kg) or prazosin (1.0 mg/kg) did not affect estrogen induced lordosis behavior. Results suggest the following conclusions: (1) blockage of either alpha or beta adrenoreceptors prevents progesterone induced lordosis behavior and (2) the adrenergic neuron involved in progesterone facilitation of lordosis behavior is not a part of the reflex arc for lordosis but probably modulates the activity of this system.