Activation of Lordotic Responding in Female Rats by Suppression of Serotonergic Activity

Abstract

After systemic administration of several serotonergic antagonists, female rats that had been ovariectomized, adrenalectomized, and estrogen-primed showed lordotic responding. Lordosis could also be elicited after direct placement of serotonergic receptor blockers into hypothalamic sites known to contain serotonergic terminals. None of the treatments activated the soliciting component of the estrous behavior pattern of the female rat. It is postulated that the hypothalamus contains serotonergic terminals which suppress lordotic responding.

Forebrain lordosis inhibiting system and serotonin neuron in female rats: Effect of P-chloroamphetamine.

“…Treatment with serotonin agonists suppressed lordosis in estrogen-progesterone primed ovariectomized rats (Everitt et al, 1974;Zemlan et al, 1977;; conversely, serotonin antagonists facilitated lordosis behavior (Zemlan et al, 1973). From neuroanatomical evidence, most of the cell bodies of serotonergic neurons are found to be located in the lower brainstem (Dahlstrom & Fuxe, 1964;Parent et al, 1981).…”

Effects of Highly or Relatively Selective 5-HT1AReceptor Agonists on Lordosis in Female Rats

“…Since lordosis is enhanced by treatment with the serotonin (5-HT) synthesis inhibitor, p-chlorophenylalanine (PCPA) (Zemlan et al , 1973), but is not enhanced in rats with a DRN lesion (Kakeyama and Yamanouchi, 1993), it appears that serotonergic neurons in the DRN play an inhibitory role in lordosis-regulation. The axons of serotonergic neurons in the DRN extend to the lordosis regulating mechanisms in the hypothalamus, including the VMH and the POA (Parent et al , 1981;Törk, 1985).…”

Concentration and Metabolism of Serotonin in Selected Brain Areas during Pregnancy and Lactation in the Rat

“…Or it may be that this reduction in serotonergic activity is a precondition for the expression of postpartum estrus behavior. It is known that serotonergic inhibition fa cilitates lordosis in the ovariectomized, estrogen-treated rat [Zemlan et al, 1973;W ard et al, 1975;E veritt et al, 1975]. Perhaps a similar relationship exists between 5-HT and the display of lordosis in the postpartum rat.…”