Sexual metabolic differences in the rat limbic brain.

BACKGROUND: There is actually limited evidence about the influence of estrogens on neuronal energy metabolism or functional cerebral asymmetry. In order to evaluate this relationship, eight male and sixteen female adult Wistar rats, divided into estrus and diestrus phase, were used to measure basal neuronal metabolic activity in some of the structures involved in the Papez circuit, using cytochrome c oxidase (C.O.) histochemistry. METHOD: We used C.O. histochemistry because cytochrome oxidase activity can be considered as a reliable endogenous marker of neuronal activity. RESULTS: We found higher C.O. activity levels in diestrus as compared to estrus and male groups in the prefrontal cortex and thalamus. Conversely, neuronal oxidative metabolism was significantly higher in estrus than in diestrus and male groups in the dorsal and ventral hippocampus (CA1 and CA3) and in the mammillary bodies. However, no hemispheric functional lateralization was found in estrus, diestrus or male groups by C.O. activity. CONCLUSIONS: These results suggest a modulatory effect of estrogens on neuronal oxidative metabolism.

The development of oxidative metabolism in diencephalic structures of the rat: a quantitative study.

A new method for quantitative determination of cytochrome oxidase (C.O.) activity was applied to diencephalic structures of the limbic system that are closely connected anatomically, that is, the mammillary bodies (MB) and the anterior nucleus of the thalamus (AT). This method makes it possible to easily evaluate the oxidative metabolic capacity of brain regions, an index of their functionality. By using this technique, we studied the postnatal development of both structures in Wistar rats of 14, 21, 30, and 120 days of age. Furthermore, animals of 730 days were included in order to evaluate the effects of aging on C.O. activity of these structures. The results showed a significant increase in the C.O. activity of the subdivisions of the AT, its levels remaining constant until the adult age, with a significant decrease in its activity in aged animals. In the MB, only the increase in C.O. activity of the medial mammillary nucleus (pars medialis) was significant until the adult age. A decrease of C.O. values with aging was significant only in the lateral mammillary nucleus. These data suggest that there is a wide heterogeneity in the maturation and aging of brain oxidative metabolism in diencephalic structures.

[Acetylcholinesterase and monoamine oxidase activity in hypothalamic structures during water deprivation]. / Aktivnost' atsetilkholinesterazy i monoaminoksidazy v strukturakh gipotalamusa pri vodnoi deprivatsii.

Light, electron microscopy and cytospectrophatometry were used to study the level of acetylcholinesterase and monoamine oxidase in the hypothalamus nuclei during different periods of water deprivation in white rats. It was demonstrated that depending upon the time of deprivation, there is a successive triggering of the cholino- adrenoreactive systems in the hypothalamus. However, the main role in the perception of water deprivation in the triggering of the regulatory mechanisms is played by the cholinergic mediator system in the lateral preoptic area, lateral and supraoptical nuclei of the hypothalamus.

Localization and characterization of phenylethanolamine N-methyl transferase in the brain of various mammalian species.

The distribution of PNMT activity in various regions and nuclei of the rat, monkey and human brain was investigated. The distribution of PNMT activity in the rat brain correlates with the distribution of PNMT immunofluorescence. The PNMT activity in the primate brain is more widely distributed than in the rat brain. High and intermediate enzyme activity values were dound in the same regions of the primate brain as in the rat brain. Intermediate or low levels were also found in various other regions of the primate brain, e.g., basal ganglia, amygdala, septum, habenula. The brain PNMT has the same substrate specificity and similar kinetic properties as the adrenal enzyme. Immunotitration studies revealed cross-reactivity between the homologous adrenal and brain PNMT.

Quantitative histochemical studies of the hypothalamus. Control point enzymes during the estrous cycle.

Three control point enzymes of the Embden-Meyerhof pathway, hexokinase (HK), phosphofructokinase (PFK) and pyruvate kinase (PK), have been measured in individual hypothalamic nuclei during the 5-day estrous cycle of adult rats by quantitative histochemical methods. PK levels, low during proestrus, rise to maximum activity during estrus; this rise is significantly greater than on all other days of the cycle in the lateral preoptic area (LP), ventromedial pars medialis (VMM) and pars lateralis (VML) and posterior hypothalamic (Post) nuclei. HK activity also rises from low proestrous levels during the cycle but, in contrast to PK, reaches maximum activity during diestrus-1 (D-1) or diestrus-2 (D-2). PFK showed variable changes during the estrous cycle with peaks occurring during estrus in some nuclei and during diestrus in others, but these changes were not significantly different. These metabolic changes occur in specific hypothalamic nuclei which have been shown by electrical stimulation, lesion production, stereotaxic hormone implantation and localization of luteinizing hormone-releasing factor experiments to have an important role in reproductive physiology and sexual behavior.

Quantitative histochemical studies of the hypothalamus: dehydrogenase enzymes following androgen sterilization.

Four enzymes, selected as representative of major metabolic pathways (malic dehydrogenase, of the citric acid cycle, lactic dehydrogenase, of glycolysis, glucose-6-phosphate dehydrogenase, of the pentose pathway and glutamic dehydrogenase, of glutamate metabolism), were measured by quantitative histochemical methods in individual hypothalamic nuclei of adult neonatally androgenized female rats. Malic dehydrogenase (MDH) was significantly reduced in nuclei of the anterior hypothalamus: the suprachiasmatic, supraoptic and anterior. Lactic dehydrogenase (LDH) increased significantly in the lateral preoptic area. Glucose-6-phosphate dehydrogenase G-6-PDH was also significantly elevated in anterior hypothalamic nuclei: medial preoptic, lateral preoptic, supraoptic and paraventricular. Glutamic dehydrogenase (GDH) was generally elevated throughout the hypothalamus with significant increases of activity occurring in the paraventricular, lateral ventromedial, arcuate, medial mamillary and posterior nuclei.

PIP: As part of a detailed analysis of the specific enzyme metabolism in individual hypothalamic nuclei during different endocrinological and behavioral states, quantitative distribution of a group of enzymes representative of major metabolic pathways was examined. Malic dehydrogenase (MDH), representative of the citric acid cycle, lactic dehydrogenase (LDH), of glycolysis, glutamic dehydrogenase (GDH), of glutamate metabolism, and glucoseo-6-phosphate dehydrogenase (G-6-PDH), of the pentose pathway, were measured in 11 hypothalamic nuclei, the cerebral cortex, and the cerebellum of adult female rats neonatally treated with testosterone propionate (TP). Several significant metabolic changes occurred in specific hypothalamic nuclei following neonatal TP (1 mg) treatment. MDH activity was significantly reduced in the suprachiasmatic (11%), supraoptic (13%), and anterior (9%) nuclei. No statistically significant changes occurred in nuclei of the middle or posterior hypothalamus. LDH was significantly elevated only in the lateral preoptic areas (23%). Several significant increases of G-6-PDH activity occurred in the following nuclei of the anterior hypothalamus: medial preoptic (32%), lateral preoptic (33%), supraoptic (13%), and paraventricular (23%). No statistically significant changes occurred in nuclei of the middle or posterior hypothalamus; these results were similar to those for MDH and LDH. GDH activity was generally elevated in all of the hypothalamic nuclei examined, except in the anterior nucleus. Significant increases of enzyme level were found in each of the major divisions of the hypothalamus. In the anterior hypothalamus, GDH activity in the paraventricular nucleus rose significantly (16%); in the middle hypothalamus, lateral ventromedial and arcuate nuclear levels were elevated (14 and 17%), and medial and posterior nuclear levels were higher than control values (32 and 36%) in the posterior hypothalamus.