Search

Delayed or direct pseudopregnancieswere induced by electrical stimulation of the cervixat 1400 h on diestrus day 2 (D-2) or on estrus,respectively. Blood samples for measurement ofprolactin and LH by radioimmunoassay were collectedby rapid decapitation at 5, 15, 30, 45 or 60min after cervical stimulation or thereafter at 3-hintervals throughout the first 6 days of leukocyticvaginal smears of pseudopregnancy (PSP L-l toL-6). For comparison, untreated animals were decapitatedat the same 3-h intervals throughout the4-day cycle. Serum LH concentrations in all the experimentalanimals did not vary from those measured in thecyclic controls. Compared with the normal cycle, prolactin (PRL)levels were not different until 10 h after cervicalstimulation during estrus. After stimulation on D-2,PRL secretion did not differ from that in the normalcycle until approximately 37 h later, when there wasa short rise following the usual proestrus surge. In both direct and delayed pseudopregnancy,twice-daily PRL surges appeared...

Delayed or direct pseudopregnancies were induced by electrical stimulation of the cervix at 1400 h on diestrus day 2 (D-2) or on estrus, respectively. Blood samples for measurement of prolactin and LH by radioimmunoassay were collected by rapid decapitation at 5, 15, 30, 45 or 60 min after cervical stimulation or thereafter at 3-h intervals throughout the first 6 days of leukocytic vaginal smears of pseudopregnancy (PSP L-1 to L-6). For comparison, untreated animals were decapitated at the same 3-h intervals throughout the 4-day cycle. Serum LH concentrations in all the experimental animals did not vary from those measured in the cyclic controls. Compared with the normal cycle, prolactin (PRL) levels were not different until 10 h after cervical stimulation during estrus. After stimulation on D-2, PRL secretion did not differ from that in the normal cycle until approximately 37 h later, when there was a short rise following the usual proestrus surge. In both direct and delayed pseudopregnancy, twice-daily PRL surges appeared on L-1 and, except for a missing nocturnal surge on L-2 in delayed PSP, continued regularly through L-6. The absence of any immediate increase of PRL following the D-2 stimulus strongly supports the view that information from the stimulus is retained in the central nervous system to be expressed later after a set of new, competent corpora lutea has been formed.

Delayed pseudopregnancy (PSP) was induced by electrical stimulation of the dorsomedial-ventromedial hypothalamus under two different experimental conditions. To induce long delay PSP, 4-day cycling rats were stimulated on the third day of pentobarbital blockade of ovulation. A similar stimulus on the afternoon of diestrus day 2 under pentobarbital resulted in short delay PSP. The parameters of electrical stimulation were as follows: biphasic 1-msec pulse pairs, 100 Hz, 200 μA peak to peak, 30/60 sec for 30 min. In animals stimulated on the third day of ovulation blockade, blood samples (