Kenneth M. Hoff

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.

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

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 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.

Rates of indoleamine synthesis in maturing mouse brain

1. 1. Rates of 5-hydroxytryptamine (5-HT) synthesis in hemispheres and brainstem of maturing mouse brain have been made. Inhibitor methods with precursor assay have been employed. 2. 2. Rates of 5-HT synthesis are higher in neonatal brain than in vitro enzyme analysis might suggest. Changes in synthetic rate are more conservative in the hemispheres. The lowest synthetic rates are generally at 1 week of age. 3. 3. The possible general significance of maturational rate patterns for 5-HT synthesis are discussed.

Monoamine oxidase inhibition and recovery in the mouse brain at various ages after birth.

Mice between the ages of 1 day postpartum and adulthood were exposed to the monoamine oxidase inhibitors tranylcypromine and pargyline. The mice were killed at seven different times following drug injection and assayed in vitro for monoamine oxidase activity in four brain regions. Inhibition and recovery of monoamine oxidase activity varied by age, and with the two inhibitors used. During the early maturational period, the potential for new monoamine oxidase synthesis was greater than normal maturational patterns of increase would suggest; and during later maturation either the proportions of various monoamine oxidase forms or their rates of synthesis are different.

Effects of parachlorophenylalanine on indoleamines in maturing mouse brain.

Abstract 1. 1. The effects of parachlorophenylalanine (PCPA), the tryptophan-5-hydroxylase (T5-H) inhibitor, on the maturation of 5-hydroxytryptamine (5-HT) and 5-hydroxy-indole acetic acid (5-HIAA) have been studied in regions of the maturing mouse brain. 2. 2. PCPA does not affect 5-HT levels in 1-day old mice treated on the day of birth, but does decrease it at all subsequent stages studied after 24 hr exposure. 3. 3. 5-HIAA level was unchanged in 1-day old and adult mice treated 24 hr earlier but was lower in almost all brain regions at other stages studied. 4. 4. The results lend support to the hypothesis that the newborn brain is able to synthesize more indoleamine than previously suspected but is unable to store it during the stages of neuronal outgrowth and terminalization.