Localization of tyrosine hydroxylase immunoreactive neurons in the forebrain of the guppy Poecilia reticulata.

The current study reports for the first time the distribution of tyrosine hydroxylase immunoreactive (TH-ir) neurons in the forebrain of the guppy Poecilia reticulata. Numerous small TH-ir neurons were observed in the olfactory bulbs, located mainly in the periphery of the bulbs. The TH-ir telencephalic neurons are localized in the ventral telencephalic area where they are grouped in three distinct nuclei (Vv,Vd and Vp) composed of a small number of cells forming a continuous strip. The largest number of forebrain TH-ir neurons was observed in the diencephalon where both small and larger neurons are present. Diencephalic TH-ir neurons are subdivided in large nuclei located in the preoptic region (nSC, nPOp and nPOm), the thalamus (nDM), the pretectal region (nPPv and nAP), the hypothalamus (nPP and nRP) and the posterior tuberculum (nPT). Many diencephalic nuclei are distributed in periventricular regions and no TH-ir cells were observed in the paraventricular organ. A comparative analysis indicates that the present observations are consistent with the general pattern of TH-ir neurons distribution reported for the forebrain of other teleosts, but with some interspecies variability present, mainly in the diencephalon. This paper also provides valuable neuroanatomical information for P. reticulata, a teleost frequently used in toxicological tests, for future studies investigating the effects of environmental pollutants on the catecholaminergic system.

Monoamine oxidase activity in embryos of pike (Esox lucius).

1. Mitochondrial MAO specific activity was measured in eggs and early embryos of the teleostean fish Esox lucius using tryptamine, 5-hydroxytryptamine (5-HT) and phenylethylamine (PEA) as substrates. 2. Tryptamine is the most readily deaminated substrate in mitochondria isolated from unfertilized eggs and embryos at the stages of cleavage, blastula and gastrula. 3. Monoamine oxidase activity gradually decreases during development and at the gastrula stage it is respectively 80% (tryptamine), 70% (5-HT) and 50% (PEA) of that found in the egg using the corresponding substrate. 4. The inhibition of egg MAO activity by clorgyline and deprenyl measured in E. lucius eggs using tryptamine as substrate, indicates the presence of a single form of MAO not corresponding to the MAO A and MAO B described in terrestrial vertebrates.

Some characteristics of mitochondrial monoamine oxidase activity in eggs of carp (Cyprinus carpio) and rainbow trout (Salmo gairdneri).

1. Monoamine oxidase (MAO) activity towards tryptamine, 5-hydroxytryptamine (5-HT) and phenylethylamine (PEA) has been measured in mitochondria isolated from carp and trout eggs. 2. In carp eggs all the tested substrates are metabolized and the highest affinity is found with tryptamine. In trout eggs a consistent level of MAO activity is obtained using tryptamine. 3. The inhibition dose-response curves of clorgyline and deprenyl indicate that both in carp and trout eggs there is only one form of mitochondrial MAO, distinct from MAO A and B which have been described in vertebrate tissues. 4. Both in carp and trout egg mitochondria a semicarbazide-sensitive amine oxidase is not involved in the deamination of the used substrates. 5. MAO found in carp and trout eggs might be involved in metabolism of some neurotransmitter monoamines during early developmental stages.

Monoamine oxidase and semicarbazide sensitive amine oxidase activities in toad liver mitochondria.

1. The deamination of 5-HT and PEA has been assayed by a radiochemical method in mitochondria isolated from toad liver. 2. Time courses of 5-HT and PEA deamination indicate that when PEA is used as the substrate, higher specific activities are obtained. 3. 5-HT is deaminated by MAO A and partially by a SSAO-like enzyme. 4. PEA is deaminated exclusively by SSAO and, MAO B activity, at least under the adopted experimental conditions, is not detectable.

Changes in monoamine oxidase activity by mitochondria isolated from late embryos of Bufo bufo.

1. Monoamine oxidase activity has been assayed in mitochondria isolated from post-neural embryos (stages 14-25) of Bufo bufo, using 5-HT and PEA as substrates. 2. Mitochondria isolated from stages 19 to 25 show an increasing ability in deaminating monoamines, PEA being metabolized at a higher level with respect to 5-HT. 3. At all the examined stages 5-HT is metabolized by an enzyme corresponding to MAO A, while PEA, from stage 19, is largely deaminated by a semicarbazide-sensitive amine oxidase (SSAO). 4. The effect of Triton X-100 on MAO A activity appears remarkably different in mitochondria isolated from embryos at stages 14 and 25 respectively.

Mitochondrial monoamine oxidase activity during preneural developmental stages of Bufo bufo.

Monoamine oxidase specific activities against PEA and 5-HT have been measured in mitochondria isolated from early embryos of Bufo bufo. During the early development up to the neural fold stage, MAO activity undergoes a continuous decrease that is more evident when PEA is used as the substrate. The inhibition patterns of deprenyl and clorgyline demonstrate that, at the neural fold stage, both type A and B MAO are present. Both in eggs and embryos MAO type A activity appears slightly more sensitive to the inhibitory effect of various concentrations (0.1-2 M) of the denaturing agent urea.

Occurrence of type A and type B monoamine oxidase activities in toad egg mitochondria.

Monoamine oxidase activity has been assayed radiochemically in mitochondria from Bufo bufo eggs. Time courses of MAO activity towards PEA and 5-HT indicate that when PEA is used as a substrate higher specific activities are obtained. The inhibition patterns by clorgyline and deprenyl demonstrate that both type A and type B MAO are present. Type A activity is more sensitive than type B to the inhibitory effect of Triton X-100. Low concentrations of 2-mercaptoethanol cause a slight stimulation of type A and B activities. Increasing concentrations result in a decrease of activity.