Peter C. Baker

The maturation of monoamine oxidase and 5-hydroxyindole acetic acid in regions of the mouse brain

Abstract Monoamine oxidase (MAO) activity and 5-hydroxyindole acetic acid (5-HIAA) amount have been measured in 4 subdivisions of the mouse brain during various stages of postnatal maturation. Each region and each indoleamine pathway component (MAO and 5-HIAA) demonstrated an individual pattern of maturation. MAO increased rapidly from day 1 postpartum and reached adult-like specific activitity by 2 weeks postpartum except in the cerebellum where increase continued after week 6. 5-HIAA levels exceeded adult-like levels by day 3 postpartum, continued to rise during the first week and reached adult level by week 6. Comparison of these data to previously reported maturational patterns of 5-hydroxytryptamine (5-HT) and 5-hydroxytryptophan decar☐ylase (5-HTPD), measured upon a similar regional basis, indicate that the components of the indoleamine pathway in the brain do not mature in a harmonious way.

Melatonin localization in the eyes of larval Xenopus

Abstract 1. 1. The larvae of Xenopus laevis, the South African clawed toad, have been assayed for melatonin levels in the lateral eyes, the whole larva and the larva minus eyes. 2. 2. Lateral eyes were found to contain somewhere between 75 to 90 per cent of the total larval melatonin.

The maturation of indoleamine metabolism in the lateral eye of the mouse.

Abstract 1. 1. The eyes of CFW albino strain mice were measured in vitro for the enzyme tryptophan 5-hydroxylase (T5-H) using a 14 C precursor; the intermediates, 5-hydroxytryptamine (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA), were isolated by differential extraction methods. 2. 2. No detectable T5-H could be measured throughout the maturational period. 3. 3. S-HT and 5-HIAA showed radical and characteristic changes during the first postnatal week; generally by the end of week 1, there is a levelling off. 4. 4. In spite of being an outgrowth of the brain, the eye has a separate, distinctly different pattern of indoleamine metabolism. 5. 5. In the mouse eye, T5-H does not appear to be the controlling factor in pathway maturation.

Effect of lithium on reproduction and postnatal growth of mice.

Mating pairs of mice were maintained continuously on drinking water containing 50 mEq/l LiCl and its effects on reproduction and postnatal development were monitored. In mating pairs put on lithium at 6-8 weeks of age, the lithium does not appear to reduce litter size at birth but it does increase postnatal mortality and the length of time between litters, and reduces the total number of litters a mating pair may have. In mating pairs put on lithium at 3 weeks of age, it severely delays postnatal growth and development of all pups in the litter. With the exception of the liver, this delayed growth and development does not appear to affect internal organs as severely as somatic body parts. This delayed growth may be the result of some effect lithium may have on certain hormones such as prolactin, thyroxine and growth hormone.

The maturation of 5-hydroxytryptophan decar☐ylase in regions of the mouse brain

Summary 5-Hydroxytryptophan decar☐ylase (5-HTPD) activity has been measured in 4 subdivisions of the mouse brain during various stages of postnatal maturation. Each region demonstrated a different pattern of maturation. During the first few days post-partum increases in enzyme activity are slower than increases in tissue weight for all regions studied. However, by the end of the first week all regions are undergoing rapid increases in enzyme activity. Maturation of the enzyme proceeds in a caudal rostral direction, with cerebellum and medulla-pons reaching adult-like status by 2 weeks, mesencephalon-diencephalon by 4 weeks and cerebral hemispheres sometime after 6 weeks. Comparisons of these enzyme data to previously reported data for 5-hydroxytryptamine (5-HT) maturation, measured upon a similar basis, indicate that the enzyme (5-HTPD) and its product (5-HT) mature differently in all regions.

Tryptophan-5-hydroxylase maturation in regions of the mouse brain.

Trytophan-5-hydroxylase (T5-H) has been measured in four subdivisions of the mouse brain during various stages of postnatal maturation. Patterns of T5-H maturation are very similar to previously measu

The effects of the specific uptake inhibitor Lu 10-171 (citalopram) upon brain indoleamine stores in the maturing mouse.

1. The specific 5-HT uptake inhibitor Lu 10-171 (Citalopram) was used to test uptake inhibition and reduced turnover in maturing mouse brain. 2. All ages showed 5-hydroxyindole acetic acid (5-HIAA) elevation indicative of inhibition and reduced turnover. Enzymatic blockade in conjunction with Lu 10-171 supported the evidence for reduced turnover. 3. The significance of early serotonergic maturation is discussed.

Precursor and End Product Effects upon Indoleamine Maturation in Mouse Brain

The effects of tryptophan loading and the acid transport inhibitor, probenecid, on the maturation of 5-hydroxytryptamine (5-HT) and 5-hydroxyindole acetic acid (5-HIAA) have been studied in the maturing mouse brain. Tryptophan loading elevates already high endogenous tryptophan at all stages studied. It does not alter 5-HT or 5-HIAA at day 1 but does elevate levels of both at later stages. Probenecid does not affect 5-HT at any age or 5-HIAA at day 1, but does cause increasingly greater elevations of 5-HIAA at later stages. The results indicate that tryptophan-5-hydroxylase is substrate saturated in early postnatal stages but not later, and that the early postnatal brain lacks an acid transport mechanism for 5-HIAA egress but develops this at later stages.

The maturation of melatonin synthesis in the lateral eyes of the mouse

Abstract 1. Melatonin and its formative enzyme, hydroxyindole- O -methyltransferase (HIOMT) were assayed in the mouse eye between one-day postpartum and adult. 2. Melatonin was not detectable in any stage of eye maturation, nor in the adult eye. 3. HIOMT activity peaked during the first week postpartum and elevated to adult values in the weeks following. 4. It is suggested that the pattern of HIOMT maturation found is a reflection of 5-hydroxyindole maturation in general in the eye.

The effect of light and dark background upon melatonin levels in larval Xenopus

Abstract 1. 1. Body melanophore numbers and spectrophotofluorometric determinations of melatonin and 5-hydroxytryptamine were made on whole Xenopus laevis larvae reared in aquaria with light and dark surfaces. 2. 2. Light background reared larvae had lower melatonin concentrations and fewer melanophores. 3. 3. Dark background reared larvae had higher melatonin concentrations and more melanophores. 4. 4. 5-Hydroxytryptamine concentrations were not significantly different in the two groups.