Gabriela Moralí

Neuroprotective effects of progesterone on damage elicited by acute global cerebral ischemia in neurons of the caudate nucleus.

BACKGROUND In addition to the hippocampus, the dorsolateral caudate nucleus (CN) and the pars reticularis of the substantia nigra (SNr) are among the most vulnerable brain areas to ischemia. A possible association of the neuronal injury in these two subcortical nuclei has been proposed, the primary damage affecting the CN GABAergic neurons innervating the SNr, and secondarily the SNr neurons as a result of an imbalance of GABAergic and glutamatergic input to the SNr. Progesterone (P(4)) exerts a GABAergic action on the central nervous system (CNS) and is known to protect neurons in the cat hippocampus from the damaging effect of acute global cerebral ischemia (AGCI). The effects of AGCI on the neuronal populations of the CN and SNr, in addition to the possible neuroprotective effects of P(4), were assessed in cats in the present study. METHODS Ovariectomized adult cats were treated subcutaneously (s.c.) with either P(4) (10 mg/kg/day) or corn oil during the 7 days before and 7 days after being subjected to a period of AGCI by 15 min of cardiorespiratory arrest followed by 4 min of reanimation. After 14 days of survival, animals were sacrificed and their brains perfused in situ with phosphate-buffered 10% formaldehyde for histologic examination. RESULTS ACGI resulted in an intense glial reaction in the CN and a significant loss (43%) of medium-sized neurons of the CN, but no difference was found in the densities of SNr neurons between controls and ischemic oil- and P(4)-treated cats. Progesterone treatment completely prevented CN neuronal loss. CONCLUSIONS The overall results point to the higher vulnerability of CN neurons to ischemia as compared to neurons in the SNr and show the protective effects of P(4) upon CN neuronal damage after ischemia.

Androgen structure and male sexual behavior in the castrated rat

Abstract The following androgens were injected sc (1 mg for 30 days) to groups of inexperienced castrated male rats: testosterone, androstenedione, androstenediol, dehydroepiandrosterone, 11 β-hydroxy-androstenedione, androsterone, dihydrotestosterone, androstanedione, androstanediol, and 5 β-androstanediol. The mating tests were performed every third day. Only testosterone, androstenedione, and androstenediol elicited the full mating pattern. Both 5 a and 5β reduced androgens were ineffective in stimulating clear sexual behavior. In contrast, two 5 a reduced androgens, androstanediol and dihydrotestosterone, were the most potent androgens to induce growth of the sex accessories. The results suggest that 5 a reduction does not play a role in the action of androgens on the brain structures related to the expression of sexual behavior in the male rat, and that the stereochemical characteristics of the androgen molecule required to elicit sexual behavior are different from those involved in androgenicity.

Post-ischemic administration of progesterone in rats exerts neuroprotective effects on the hippocampus.

Progesterone is neuroprotective in models of focal or global ischemia when treatment starts either before the insult or at the onset of reperfusion. In these cases the steroid may act during the occurrence of the early pathophysiological events triggered by ischemia or reperfusion. As opposed to this condition, the aim of the present study was to assess the effect of delayed, post-injury administration of progesterone on the preservation of pyramidal neurons of the hippocampus of rats 21 days after been exposed to global ischemia by the four vessel occlusion model. Progesterone (8 mg/kg, i.v.) or its vehicle, were administered at 20 min, 2, 6, and 24h after the end of ischemia. At histological examination, brains of the ischemic vehicle-treated rats showed a severe reduction of the population of pyramidal neurons in the CA1 and CA2 subfields (12% and 29% remaining neurons, respectively), and a less severe neuronal loss in the CA3 and CA4 subfields of the hippocampus (68% and 63% remaining neurons, respectively), as compared to rats exposed to sham procedures. They also showed a two-fold enlargement of the lateral ventricles and 33% shrinkage of the cerebral cortex as compared to the sham group. Progesterone treatment resulted in a significant preservation of pyramidal neurons in CA1 and CA2 (40% and 62% remaining neurons), with no ventricular dilation and only a mild (12%) cortical shrinkage. Results suggest that progesterone is able to interfere with some late pathophysiological mechanisms leading both to selective neuronal damage in the hippocampal CA1 and CA2 subfields, and to shrinkage of the cerebral cortex.

Melatonin and ischemia–reperfusion injury of the brain

Abstract:  This review summarizes the reports that have documented the neuroprotective effects of melatonin against ischemia/reperfusion brain injury. The studies were carried out on several species, using models of acute focal or global cerebral ischemia under different treatment schedules. The neuroprotective actions of melatonin were observed during critical evolving periods for cell processes of immediate or delayed neuronal death and brain injury, early after the ischemia/reperfusion episode. Late neural phenomena accounting either for brain damage or neuronal repair, plasticity and functional recovery taking place after ischemia/reperfusion have been rarely examined for the protective actions of melatonin. Special attention has been paid to the advantageous characteristics of melatonin as a neuroprotective drug: bioavailability into brain cells and cellular organelles targeted by morpho‐functional derangement; effectiveness in exerting several neuroprotective actions, which can be amplified and prolonged by its metabolites, through direct and indirect antioxidant activity; prevention and reversal of mitochondrial malfunction, reducing inflammation, derangement of cytoskeleton organization, and pro‐apoptotic cell signaling; lack of interference with thrombolytic and neuroprotective actions of other drugs; and an adequate safety profile. Thus, the immediate results of melatonin actions in reducing infarct volume, necrotic and apoptotic neuronal death, neurologic deficits, and in increasing the number of surviving neurons, may improve brain tissue preservation. The potential use of melatonin as a neuroprotective drug in clinical trials aimed to improve the outcome of patients suffering acute focal or global cerebral ischemia should be seriously considered.

Long-term morphological and functional evaluation of the neuroprotective effects of post-ischemic treatment with melatonin in rats

Abstract:  Consensus on neuroprotection has pointed out the relevance of the long‐term morphological and functional evaluation of the effectiveness of putative neuroprotective procedures. In the present study, place learning (Morris water maze) and working memory (eight‐arm Olton radial maze) were evaluated in adult male rats 90 days after 15 min of global cerebral ischemia (four‐vessel occlusion) followed by continuous i.v. infusion (10 mg/kg/hr) of melatonin (Isch + Mel) or vehicle (Isch + Veh) for 6 hr, and the pyramidal neuron population of the cornus Ammoni (CA) of the hippocampus and layers III and V of the medial prefrontal cortex was assessed at the end of the behavioral testing period (120 days after ischemia). Impairment of place learning, a significant delay in working memory acquisition, and a significant loss of pyramidal neurons in the Ammons horn (CA1: 23%, CA2: 52% CA3: 73%, hilus: 64% remaining neurons), were observed in the Isch + Veh group. By contrast, a similar performance of the Isch + Mel group to that in the Intact and Sham groups and better than that of the Isch + Veh group, besides a significant reduction of pyramidal neuron loss in the CA subfields (CA1: 79%, CA2: 88% CA3: 86%, hilus: 72% remaining neurons), documented that melatonin treatment led to a long‐term preservation of both the neural substrate, and the capability for integration of spatial learning and memory, mainly dependent on a normal hippocampal functioning. Overall the results emphasize the efficacy of melatonin in counteracting the pathophysiological processes induced by ischemia, by exerting its actions during a short but critical period early after the ischemic episode.

Long-term study of dendritic spines from hippocampal CA1 pyramidal cells, after neuroprotective melatonin treatment following global cerebral ischemia in rats

Melatonin reduces pyramidal neuronal death in the hippocampus and prevents the impairment of place learning and memory in the Morris water maze, otherwise occurring following global cerebral ischemia. The cytoarchitectonic characteristics of the hippocampal CA1 remaining pyramidal neurons in brains of rats submitted 120 days earlier to acute global cerebral ischemia (15-min four vessel occlusion, and melatonin 10mg/(kg h 6h), i.v. or vehicle administration) were compared to those of intact control rats in order to gain information concerning the neural substrate underlying preservation of hippocampal functioning. Hippocampi were processed according to a modification of the Golgi method. Dendritic bifurcations from pyramidal neurons in both the oriens-alveus and the striatum radiatum; as well as spine density and proportions of thin, stubby, mushroom-shaped, wide, ramified, and double spines in a 50 microm length segment of an oblique dendrite branching from the apical dendrite of the hippocampal CA1 remaining pyramidal neurons were evaluated. No impregnated CA1 pyramidal neurons were found in the ischemic-vehicle-treated rats. CA1 pyramidal neurons from ischemic-melatonin-treated rats showed stick-like and less ramified dendrites than those seen in intact control neurons. In addition, lesser density of spines, lower proportional density of thin spines, and higher proportional density of mushroom spines were counted in ischemic-melatonin-treated animals than those in the sinuously branched dendrites of the intact control group. These cytoarchitectural arrangements seem to be compatible with place learning and memory functions long after ischemia and melatonin neuroprotection.

Effects of castration and sex steroid treatment on the motor copulatory pattern of the rat

Abstract The effect of castration and sex steroid (testosterone propionate, TP or estradiol benzoate, EB) treatment on the motor copulatory pattern was studied by an accelerometric technique in 14 male Wistar rats. This technique allows precise measurements of the following parameters: (a) duration of mounts (M), intromissions (I) and ejaculations (E); (b) thrusting frequency, and (c) amplitude of pelvic movements. Analysis of the signals generated during M, I or E, allows clear differentiation among the three behavioral patterns. Castration abolished sexual activity in most of our rats. The motor copulatory pattern was analyzed in four castrated rats, which continued to display sexual behavior for some time after castration. Castration did not alter thrusting frequency nor vigor of mounting. Duration of M, but not that of I or E, was prolonged by castration. TP (5 mg/day) restored sexual behavior to precastration levels in all 6 TP-treated rats. The motor copulatory pattern of the TP-treated rats was similar to that of intact rats. EB treatment (5 μg or 50 μg/day) induced mounting in 6 out of 7 subjects, but only two rats ejaculated once. EB failed to restore M duration to precastration levels and increased the frequency of pelvic thrusting above control values. Present results suggest that estrogen in large dosages exerts subtle effects on the motor copulatory pattern of the rat.

Patterns of motor and seminal vesicle activities during copulation in the male rat

The interaction between behavioral and visceral events during copulation was studied in nine intact adult male Wistar rats. The motor copulatory pattern was analyzed by an accelerometric technique and the seminal vesicle pressure (SVP) was recorded through a catheter chronically inserted into the right seminal vesicle. Mounting was associated with a small broad rise in SVP that often preceded the initiation of pelvic thrusting. Penile insertion resulted in a second sharp rise in SVP superimposed on the primary wave related to mounting. A steep rise in SVP occurred during the performance of the motor ejaculatory pattern after a variable period of intravaginal thrusting. This final rise was associated with ejaculation. Analysis of the temporal relationships ships between the SVP changes and copulatory behavior revealed that each of the three rises of SVP was related to distinct patterns of stimulation, suggesting that they were mediated by separate reflex arcs.

Neuroprotective effects of progesterone and allopregnanolone on long-term cognitive outcome after global cerebral ischemia

PURPOSE To assess the longterm neuroprotective effects of progesterone (P₄) and allopregnanolone (ALLO) on functional and morphological parameters of the integrity of the hippocampus, after global cerebral ischemia. METHODS Adult male Sprague-Dawley rats were subjected to a transient severe (20 min) forebrain ischemia (Isch) episode and treated with P₄ or ALLO (8 mg/kg i.v.) or its vehicle, at 20 min, 2, 6, 24, 48 and 72 h after ischemia. Rats subjected to Sham procedures, and intact rats were included as nonischemic controls. Three months after ischemia, both the functional (spatial learning and memory, and reference and working memory), and the morphological integrity (dimensions of the hippocampal formation, thickness of the CA1 subfield, and pyramidal neuron population) of the hippocampus and the medial prefrontal cortex(mPFC) were determined. RESULTS Treatment with P₄ or ALLO significantly reduced the impairment in spatial learning and memory, as well as in reference and working memory, and prevented the narrowing of the hippocampus, otherwise induced by ischemia. This better performance of P₄ and ALLO treated rats than vehicle (Veh) treated rats, occurred in spite of a loss of pyramidal neurons in the CA1, CA2,CA3 and hilus subfields of the Ammons horn (remaining neurons: Isch+Veh: 21.0, 35.6, 44.1, and 40.3%; Isch+P₄: 19.9, 32.2,41.1, and 32.5%; Isch+ALLO: 25.5, 62.0, 73.7, and 56.7%), and nonsignificant changes in the mPFC, as compared to the Intact group (100%). CONCLUSIONS Performance of P₄ or ALLO treated rats in learning and memory tests suggests that these steroids promoted neural conditions accounting for adequate functioning long after ischemia, in spite of the loss of hippocampal pyramidal neurons.

Characteristic frequency bands of the cortico-frontal EEG during the sexual interaction of the male rat as a result of factorial analysis

The electrocorticogram (ECoG) from the prefrontal cortex was simultaneously recorded with the accelerometric signals of pelvic thrusting performed by male rats during sexual behavior. The changes in the prefrontal ECoG were precisely correlated in time with well defined elements of male rat copulation. Principal component analysis allowed to identify three distinct bands of frequencies in the frontal ECoG: the absolute power (AP) of the 4-16 Hz band was increased in the 500-ms periods before, during, and after the execution of pelvic thrusting in mount, intromission and ejaculation responses; the AP of the 18-24 Hz band was selectively increased during the execution of pelvic thrusting at the three copulatory responses, whereas the AP of the 26-32 Hz band was increased only during the pelvic moments of mount and intromission responses. These results show that the electroencephalographic activity of the prefrontal cortex of the male rat is related to the performance of sexual behavior, supporting the concept that this cortical area is involved in the organization of sequential behaviors, as sexual behavior.