Pattern of [14C]2-deoxyglucose concentration associated with potentiation of reproductive behavior by prostaglandin E2.

One indication of receptive behavior of the female leopard frog, Rana pipiens, is absence of a release call during tactile stimulation of the trunk. Prostaglandin E2 (PGE2) inhibits this call. This experiment demonstrates a different pattern of [14C]2-deoxyglucose concentration in brains of 5 receptive females silenced by 1 microgram/g PGE, compared with that in 3 unreceptive, vocalizing controls injected with deionized water. 14C concentrations were measured in areas important for vocalization in frogs, in limbic system structures and in parts of the brain that receive somatosensory input. There was high activity relative to the rest of the brain in the receptive, silent PGE2-treated females in the caudal part of the anterior preoptic nucleus, in the dorsal habenula, and in the dorsal tegmental area of the medulla lateral to the pretrigeminal nucleus.

Egg-oviduct interaction initiates reproductive behavior.

The experiments reported in this paper provide evidence that eggs must pass through the oviducts in order for receptivity to occur after ovulation in the female frog, Rana pipiens. In one experiment, oviductectomized frogs remained unreceptive after ovulation was induced by administration of exogenous pituitary glands, while sham-operates became receptive within 48 hr. Another experiment had four groups of subjects: ovariectomized females, females with oviducts ligated at the ostial end, females with openings in the uteri that prevented eggs from accumulating there, and sham-operated females. Only the last two groups, groups in which eggs could pass through the oviducts, became receptive. In these experiments, receptivity was indicated by absence of the release call during manual clasping of the trunk. Earlier experiments have shown that eggs have to pass through the oviducts in order to become fertilizable. Thus, the passage of eggs through the oviducts provides a mechanism which links the onset of reproductive behavior to the availability of fertilizable gametes.

Hormonal basis for breeding behavior in female frogs: vasotocin inhibits the release call of Rana pipiens.

Inhibition of the release call in gravid female frogs facilitates maintenance of the male's clasp so that oviposition and spawning can occur. Arginine-8 vasotocin inhibits the release call by causing an accumulation of water and internal pressure.

Initiation and inhibition of the release croak of Rana pipiens.

A release croak is emitted by unreceptive female frogs when they are clasped by males; receptive females are silence. This report investigates the sources of stimuli which initiate and inhibit the release croak of Rana pipiens. Experiment 1 demonstrates that manual clasping of the trunk rather than the legs elicits the croak. Experiment 2 shows that denervation of the skin of the trunk prevents the release call in response to manual stimulation. Experiment 3 confirms that artificial distension of the body with fluid inhibits the release croak in response to manual stimulation. Experiment 4 shows that artifically-distended females, who are not in the normal endocrinological state that accompanies mating, are silent and receptive in response to clasping by sexually-active male frogs. The first two experiments imply that stimulation of the skin of the trunk initiates the release croak; Experiments 3 and 4 suggest that an internal afferent source inhibits the release croak and might mediate an important aspect of receptivity in female frogs.