The Durk Pearson & Sandy Shaw®
Life Extension NewsTM
Volume 11 No. 1 • January 2008

Last night I had a nightmare . . . I woke up in a cold sweat, thinking of what Bishop Samuel Wilberforce’s wife reputedly said when confronted with Darwin’s theory: ‘Let us hope it is not true. But if it is, let us hope it does not become widely known.’
— Dan Graur
Dept. of Biology and Biochemistry, University of Houston
(in a letter to Nature)

As a teenager, when I had the chance to meet him in 1946, I was bold enough to ask, ‘Mr. Winston Churchill, sir, to what do you attribute your success in life?’ He replied, instantly: ‘Conservation of effort: never stand up when you can sit down and never sit down when you can lie down.’
— Paul Johnson, historian
Imprimis, December 2007

The improver of natural knowledge absolutely refuses to acknowledge authority, as such. For him, skepticism is the highest of duties, blind faith the one unpardonable sin.
— T. H. Huxley
“On the Advisableness of Improving Natural Knowledge” (1866)

We cannot solve the problems we have created with the same thinking that created them.
— Albert Einstein

Enhancing Learning and Memory and Neurogenesis with Tryptophan-Induced Serotonin Increase

Neurogenesis, the creation of new neurons, is now known to be a lifelong process that takes place in two particular areas of the brain in several species, including rodents, tree shrews, dogs, and humans. Decrease of neurogenesis is thought to be related to cognitive decline with aging. For example, in adult rats, mice, and tree shrews, rates of neurogenesis begin to slow by the age of 1 year, well before the onset of old age.1 A new study1 reports that newly generated cells (in the dentate gyrus of the hippocampus) of marmoset monkeys were significantly lower in older animals and decreased linearly with age. These changes occurred before the onset of old age, “suggesting the possibility that similar alterations occur in the human brain.”

The authors further explained that a factor that may be involved in the age-related decline is the decrease with age of “serotonin, a neurotransmitter that promotes hippocampal neurogenesis through actions at the 5-HT1a receptor [a certain serotonin receptor].” Both serotonin and the 5-HT1a receptor decrease with age, “raising the possibility of a negative effect on neurogenesis.”

Another study2 reported that serotonin-induced increases in neurogenesis in 8-week-old Wistar rats were mediated through different and common 5-HT (serotonin) receptor subtypes in two brain areas, the dentate gyrus and the subventricular zone. The same laboratory had reported in an earlier study that “significant decreases in the number of newborn cells in the SVZ [subventricular zone] and SGL [subgranular layer of the dentate gyrus] are observed following either acute or chronic 5-HT depletion.”

A very recent study3 reports that the enhanced serotonergic neurotransmission in the hippocampus following tryptophan administration improves learning acquisition and memory consolidation in Wistar rats. The rats were given oral doses of 50 mg/kg body weight or 100 mg/kg body weight of tryptophan daily for 6 weeks. Long-term memory in the water maze test was significantly improved by 66.5% at the 50-mg/kg dose and by 72.4% at the 100-mg/kg dose. Short-term memory improved significantly by 54% at the 100-mg/kg dose but did not show any effects at the 50-mg/kg dose. Memory consolidation was tested by determining the retention latency (how long it took the rats to relocate the hidden platform) at 1 hour and 24 hours after training. There was a significant decrease in retention latency at both doses of tryptophan after 24 hours.

Durk & Sandy Tryptophan Formulations

We are both very happy that tryptophan is back on the market after a prolonged and unjustified FDA ban. We have two Serene Tranquility™ tryptophan formulations, one for daytime (with 550 mg tryptophan/tablespoon of powder) and the other for bedtime (also with 550 mg tryptophan/tablespoon of powder, plus melatonin). We also have a day and bedtime 5-hydroxytryptophan formulation. The difference between tryptophan and 5-hydroxytryptophan is that 5-hydroxytryptophan is one step closer to the final product, serotonin. Our tryptophan is purchased exclusively from Ajinomoto, a highly reputable firm with extensive experience in producing amino acids, whose tryptophan was not associated with the EMS (eosinophilic myalgia syndrome) that poisoned about 2000 people in the late 1980s.


  1. Leuner et al. Diminished adult neurogenesis in the marmoset brain precedes old age. Proc Natl Acad Sci USA 104(43):17169-73 (2007).
  2. Banasr et al. Serotonin-induced increases in adult cell proliferation and neurogenesis are mediated through different and common 5-HT receptor subtypes in the dentate gyrus and the subventricular zone. Neuropsychopharmacology 29:450-60 (2004).
  3. Haider et al. Enhanced serotonergic neurotransmission in the hippocampus following tryptophan administration improves learning acquisition and memory consolidation in rats. Pharmacol Rep 59:53-7 (2007).

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