First Advisor

Leonard Simpson

Date of Publication


Document Type


Degree Name

Master of Science (M.S.) in Biology




Tryptophan, Progesterone, Estrogen, Mesencephalon, Guinea pigs -- Physiology



Physical Description

1 online resource (2, vii, 64 p.)


Progesterone stimulates prolactin secretion in estrogen ( estradiol-17-~)primed monkeys and guinea pigs. It is hypothesized that the serotonin neural system plays a pivotol role in mediating the effect of progesterone on prolactin secretion. Indeed, progesterone, but not estrogen, increases serotonin levels in the midbrain raphe in guinea pigs. However, estrogen alone stimulates gene expression of the rate-limiting enzyme for serotonin synthesis, tryptophan hydroxylase (TPH), and progesterone supplement to the estrogen regimen has no additive effect, as indicated by TPH mRNA levels in monkeys. The discrepancy between ovarian steroid effects on the TPH mRNA level and the serotonin level might be due to actions of progesterone on post-transcripitonal processing of the TPH gene. In this experiment, TPH protein levels were measured in the midbrain raphe in guinea pigs. Guinea pigs were ovariectomized (OVX; n=5), estrogen-treated (28 d; n=6), and estrogen plus progesterone-treated (14 d of estrogen and 14 day of estrogen plus progesterone; n=5). Western analysis by chemiluminescence with densitometric analysis was performed to detect and measure TPH protein levels. Hypothalamic levels of neurotransmitters were also measured with high performance liquid chromatography. The results showed that estrogen increased the TPH protein level significantly compared to the OVX group (p


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