The administration of the putative 5-hydroxytryptamine1 (5-HT1) agonist 8-hydroxy-2(di-n-propylamino)
tetralin (8-OH-DPAT) (0.0625-1.0 mg X kg-1) suppresses
lordosis behaviour induced in ovariectomized female rats by daily treatment for 3-5 days with
estradiol benzoate (1.25 micrograms/rat). A similar suppressive effect on the
lordosis behaviour can be obtained by administration of the
dopamine/
serotonin agonist,
lisuride (0.1-0.4 mg X kg-1), or after the administration of the
dopamine (DA) agonists,
apomorphine (0.2-0.8 mg X kg-1) or
quinpirole (0.75-2.50 mg X kg-1). The suppressive effects on the
lordosis behaviour by
8-OH-DPAT cannot be antagonized by the DA receptor antagonist
haloperidol (0.2 mg X kg-1) neither with methiotepin (0.5 mg X kg-1), which is assumed to be a non-selective
5-HT receptor blocking agent, nor with
pirenperone (0.25 mg X kg-1) which is assumed to be a 5-HT2 receptor blocking agent. However, a partial blockade of the
lordosis suppressive effects of
8-OH-DPAT was obtained by treatment with (-)-
pindolol, which is thought to be a partial 5-HT1 blocking agent, suggesting that
8-OH-DPAT exerts its suppressive effects on the
lordosis behaviour through the
5-HT system.
Haloperidol causes a complete blockade of the suppressive effects of
apomorphine and
quinpirole suggesting that these drugs exert their inhibitory effects on the
lordosis behaviour by activating the DA system.(ABSTRACT TRUNCATED AT 250 WORDS)