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      Strain Differences for Preoptic Stimulation of Ovulation in Cyclic, Spontaneously Persistent-Estrous, and Androgen-Sterilized Rats

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          Abstract

          The CD (Charles River) strain of rats differs in several important respects from our inbred Osborne Mendel (O-M) strain. The critical period for the ovulatory surge of gonadotropin in proestrus is less sharply limited in CD rats. They are much more refractory to preoptic (POA) electrochemical stimulation for ovulation, not only in normally cycling females, but strikingly so in androgen-sterilized (TP) females, as well as in rats having spontaneous persistent estrus (PE). In proestrous 4-day cyclic CD females ‘blocked’ with pentobarbital, a much larger stimulus (100 µA × 30 sec = 3000 µcoulombs) was required to fully ovulate all subjects than was needed in similar O-M rats (10 µA × 20 sec = 200 µcoulombs). While 5/6 O-M PE rats ovulated in response to massive unilateral POA stimulation (3000 µcoulombs), all of 6 CD PE rats failed to ovulate. Even bilateral POA stimulation with these parameters induced ovulation in only 3/10 rats. O-M TP rats had low POA thresholds close to those of cyclic O-M females, while only 1/6 CD TP rats gave even a partial response (5 tubal ova) to massive bilateral stimulation. CD TP rats also differed from O-M TP rats by secreting abundant prolactin in spite of the constant estrus. This was shown by prominent milk cysts in the mammary glands at 8–9 months of age and by spontaneous pseudopregnancy after corpora lutea were induced by LH injection. O-M TP rats had no mammary development and experienced only a short diestrus after LH injection. Whether there is a common basis for these strain differences remains uncertain.

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          Author and article information

          Journal
          NEN
          Neuroendocrinology
          10.1159/issn.0028-3835
          Neuroendocrinology
          S. Karger AG
          0028-3835
          1423-0194
          1970
          1970
          19 March 2008
          : 6
          : 2
          : 98-108
          Affiliations
          Department of Anatomy, Duke University School of Medicine, Durham, North Carolina, USA
          Article
          121912 Neuroendocrinology 1970;6:98–108
          10.1159/000121912
          4910153
          © 1970 S. Karger AG, Basel

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          Page count
          Pages: 11
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