Biomedical subjects

A M Aloisi

Publications and source records attributed to A M Aloisi.

At least 19 recordsLinked to original sources

PubMed2006

Single opioid administration modifies gonadal steroids in both the CNS and plasma of male rats.

While morphine remains one of the most widely used opioids for the treatment of painful conditions, other opioids are also commonly employed. Because of the interactions between opioids and gonadal hormones, in particular opioid-induced hypogonadism, this study investigated the effects of widely used opioids on plasma testosterone and estradiol levels and brain testosterone levels in male rats. Animals were s.c. injected with two concentrations of morphine (5 or 10 mg/kg), fentanyl (0.05 or 0.1 mg/kg), tramadol (10 or 40 mg/kg), buprenorphine (0.05 or 0.1 mg/kg) or saline (0.7 ml/kg). Four or 24 h after treatment, the rats were deeply anesthetized to collect blood samples from the abdominal aorta and to perfuse the brains with saline. Plasma and brain hormone levels were measured by radioimmunoassay. In rats studied 4 h after treatment, all the opioids except tramadol 10 mg/kg decreased plasma testosterone in comparison with saline administration. At the same time, plasma estradiol levels were lower than control in the groups treated with the low doses of morphine, tramadol and buprenorphine, while estradiol remained at control levels in the other groups. Twenty-four hours after treatment, plasma testosterone levels were different (higher) than control in the animals treated with the low doses of morphine, fentanyl and buprenorphine. Estradiol was lower than control in the low dose groups, while the high doses did not produce any changes with respect to control. Four hours after treatment, brain testosterone was drastically decreased in all groups except buprenorphine, in which it remained at control levels. All groups returned to control levels at 24 h after treatment. In conclusion, opioids exert important effects on plasma and CNS sex hormone levels. The different magnitude and time-course of the effects of the different opiates on testosterone and estradiol levels are likely due to their different mechanism of action.

Analgesics, Opioid↗

PubMed2001

Bisphenol-A differently affects estrogen receptors-alpha in estrous-cycling and lactating female rats.

The effect of long-term exposure to bisphenol-A (BPA) on estrogen receptor-alpha (ER) immunoreactivity was studied in the medial preoptic area, arcuate nucleus and the ventromedial nucleus of the hypothalamus of estrous cycling and lactating female rats. Pregnant/lactating or estrous cycling rats were exposed to BPA (40 mg/Kg/day) or peanut oil. Lactating females showed fewer ER-immunoreactive cells than non-lactating females in the medial preoptic area and ventromedial nucleus of the hypothalamus. BPA induced an increase in ER-immunoreactive cells in the medial preoptic nucleus irrespective of lactation. BPA only induced a decrease in ER-immunoreactive cells in the arcuate nucleus of the lactating group; oil induced an increase in ER-immunoreactive cells in the lactating with respect to non-lactating group. The results demonstrate that exposure of adult females to BPA modifies the number of ERs.

Animals↗

PubMed2001

Effects of gonadal hormones and persistent pain on non-spatial working memory in male and female rats.

There are indications of a modulatory role carried out by gonadal hormones and pain in cognitive functions. We have examined this issue in male and female rats by assessing the impact of gonadectomy and persistent pain on the object recognition test. Intact and gonadectomized male and female rats were exposed to an open field (15 min) in which three objects were placed (Trial 1); the same test was repeated 2 h later (Trial 2), after the replacement of a "familiar" object with a novel one. Three days later (Day 2), the same procedure was repeated (Trial 3 and 4 with 2 h in between) but half of the animals were exposed to formalin-injection immediately before Trial 3. The latency, frequency and duration of approaching the three objects were recorded in each trial and compared by sex, gonadectomy and formalin treatment. The results showed that gonadectomized males and females had lower levels of approach to all objects and less locomotor/exploratory activity than intact animals in all experimental trials; their behaviour was not affected by repetition of the test or by pain. On Day 1, intact males showed a higher level of approach to the novel object than females. In intact males, the 2 h delay between the first and second trial failed to induce any significant modification of exploration of the novel object with respect to the familiar one, while in intact females the novel object was approached much less than the familiar one. Similarly on Day 2, the novel object was approached for a longer time by intact males than by all the other groups. In conclusion, our data show that physiological levels of circulating gonadal hormones significantly affected the performance of male but not female rats when exposed to the object recognition test.

Animals↗

PubMed2001

Effects of gonadectomy and pain on interferon-gamma production in splenocytes of male and female rats.

The role of gonadal hormones and persistent pain (formalin test) in the regulation of interferon-gamma (IFN-gamma) production in splenocytes was investigated in male and female rats. Animals were either sham-operated (Intact) or gonadectomized (GDX) and, 3 weeks later, were subcutaneously injected with formalin (50 microl, 10%) or only pricked with a syringe needle in the dorsal hind paw. Sixty minutes after treatment the animals were deeply anesthetized and the spleens were dissected under aseptic conditions. Blood was collected from the abdominal aorta for measurement of plasma steroids. IFN-gamma production was determined in vitro in the splenocytes after Con A stimulation. Splenocytes of Intact females showed higher IFN-gamma production than those of Intact males. This sex difference disappeared in GDX animals because of the lower levels in GDX females. Formalin decreased IFN-gamma in both Intact and GDX groups. In females, there was a positive correlation between IFN-gamma production in splenocytes and plasma estradiol levels. The present data demonstrate a sex difference in IFN-gamma production (due to the immunostimulating effect of estradiol in females) and an immunodepressive role of pain in both sexes.

Animals↗

PubMed2000

Gonadectomy and persistent pain differently affect hippocampal c-Fos expression in male and female rats.

Hippocampal c-Fos expression was studied in male and female rats after gonadectomy and persistent pain. Three weeks after surgery, animals were sham- or formalin-injected (50 microl, 10%) and placed in a familiar testing apparatus. The formalin-evoked licking, flexing and jerking of the injected paw were recorded for 60 min, c-Fos was determined in the dorsal and ventral hippocampus: dentate gyrus (DG), CA1 and CA3. Gonadectomy induced higher c-Fos in the dorsal DG of both sexes, in all ventral subfields of males and in the ventral CA3 of females. In normal males and females, formalin increased c-Fos in the dorsal DG and in the male ventral subfields. In gonadectomized ones formalin decreased or did not change c-Fos. Gonadectomy induced longer flexing in males and females. These data indicate an important and sex-dependent interaction between gonadal hormones, nociceptive input and neuronal activity in the hippocampus.

Analysis of Variance↗

PubMed2000

Role of gonadal hormones in formalin-induced pain responses of male rats: modulation by estradiol and naloxone administration.

The aim of this study was to assess the possible mediation of endogenous opioids in the effects of gonadal hormones on the responses to formalin pain. We studied the effects of intracerebroventricular injection of estradiol and/or naloxone on the magnitude and time-course of the formalin-evoked behavioural and hormonal responses of intact and gonadectomized male rats. Animals were gonadectomized or left intact; on days 20 and 21 after surgery, they were intracerebroventricularly injected with 17beta-estradiol (1 microg/5 microl) or saline. On day 22, the animals received naloxone (2.5 microg/5 microl) or saline intracerebroventricularly and then, 15 min later, were subcutaneously injected with formalin (50 microl, 5%) or only pricked with a syringe needle in the dorsal hindpaw. The rats were then introduced to a testing apparatus where the formalin-induced licking, flexing and jerking of the injected limb and the other spontaneous behaviours were recorded for 60 min. At the end of the test, the animals were killed and blood was collected from the trunk. Gonadectomy and naloxone increased flexing duration independently of the other treatments. In gonadectomized rats, estrogen increased licking duration and decreased paw-jerk frequency during the first phase (0-15 min) of the formalin test. During the second phase (16-60 min), licking was increased by estrogen only in intact animals. Treatment with naloxone completely abolished all these modifications. The three measures of activity (rearing, inner and outer crossing) showed that while in sham-treated animals the gonadectomy-induced decrease in activity was completely counteracted by estrogen administration, in formalin-treated animals the gonadectomy-induced decrease was not affected by estrogen. In fact, estrogen appeared to further depress the motor activities in the formalin groups. Naloxone reversed these modifications only for outer crossing frequency, blocking the gonadectomy-induced decrease in sham-treated animals. Corticosterone plasma levels were increased by formalin only in estrogen-treated animals, independently of naloxone. In conclusion, these data indicate an important role of both male gonadal hormones and estrogen in formalin-pain responses, acting through opiate and non-opiate mechanisms.

Animals↗

PubMed1999

Oxotremorine-induced modifications of the behavioral and neuroendocrine responses to formalin pain in male rats.

In the present investigation, the antinociceptive effects of the muscarinic cholinergic agonist, oxotremorine, were evaluated in rats using the formalin test. In Expt. 1, two oxotremorine concentrations (0.1 and 0.2 mg/kg) and two administration times (15 and 1 min before formalin injection) were chosen. All spontaneous and formalin-evoked behavioral responses were considered. In Expt. 2, only the higher concentration of oxotremorine (0.2 mg/kg) was administered 15 or 1 min before the formalin test. The animals were killed 15, 30 or 60 min after formalin treatment. Blood was collected from the trunk to determine corticosterone plasma levels. Some brain areas (hypothalamus, septum and periaqueductal gray matter) were dissected for determination of the beta-endorphin content. Oxotremorine induced a dose- and time-dependent reduction of all formalin-evoked responses: licking was decreased during both the first and second phases of the formalin test, flexing was decreased during the second phase by the higher concentration only and paw-jerk was decreased during the first phase by both concentrations. Rearing and line-crossing were significantly decreased by oxotremorine while exploratory activity was only partially reduced; self-grooming was increased. These effects on exploratory activity and self-grooming were abolished by formalin treatment. beta-endorphin content in the septum was increased by oxotremorine administered 15 min, but not 1 min, before formalin-treatment. beta-endorphin in the hypothalamus increased in all formalin-treated groups independently of oxotremorine administration. These results confirm, and extend to tonic pain, the analgesic effect exerted by oxotremorine on phasic responses. Because of the different effects on each formalin-induced response, they also indicate both spinal and supraspinal CNS sites of action.

Analysis of Variance↗

PubMed1999

Effects of novelty and pain on behavior and hippocampal extracellular ACh levels in male and female rats.

In vivo microdialysis was used to assess the effects of novelty and pain on hippocampal ACh release in male and female rats. Experiments were carried out during the dark phase and consisted of 2 days of tests: on Day 1, after Baseline 1, animals were exposed to a new cage (Novelty) to which, 30 min later, a plastic cylinder (Object) was introduced. On Day 2, after Baseline 2, the Formalin test (50 microl of formalin 10%, s.c. injected in the dorsal hindpaw) was carried out in the animal's home cage. All behaviors were recorded. The extracellular levels of ACh in the dorsal hippocampus were estimated, in 10-min samples, by assay of ACh in the dialysates by HPLC. On Day 1 the raw values of ACh were higher in females than in males, but no sex difference was present when the percentage of change was considered. In both sexes the Novelty and Object tests induced an increase in ACh levels with respect to Baseline. Higher levels of exploration were present in females than males during the first 10 min of Novelty. On Day 2, ACh release increased in both sexes during the Formalin test. No sex difference in either ACh raw values or the percentages of change were found. Females showed higher levels of licking and lower levels of activity than males. The present study shows that novelty and pain induce similar hippocampal cholinergic activation in male and female rats but different behaviors. The results are discussed in light of the several anatomical and functional sex differences present in the hippocampus.

Acetylcholine↗

PubMed1999

Effect of behavioral stress on platelet reactivity on polymeric surfaces.

It is well known that stressful stimuli change blood functions and platelet parameters are altered in humans and animals subjected to stress. We have examined the influences of behavioral stress on the morphological responses of platelets on a standard biomaterial, polyethylene (PE). Male rabbits were used. Blood was collected from the marginal vein of the ear 2 times per subject: the first sample was used as the baseline; 1 week later, the second was preceded in half of the subjects by 20 min of immobilization stress. In vitro adhesion of platelets on the PE was evaluated. The exposure of animals to stress induced a dramatic change in platelet morphology and functions on the PE: a higher degree of platelet adhesion, increased platelet spreading, and the appearance of pseudopodia. In the unstressed subjects there were no modifications of the platelets on the PE with respect to the baseline. The present experiment emphasizes for the first time the possible problems involved with the varying physiological conditions of patients before and after any biomaterial application surgery and of subjects who supply the blood for hemocompatibility tests performed on biomaterials. Therefore, in assessments of the performance of different biomaterials, the reactivity of blood factors in the patients should be considered and the test of blood compatibility should be performed with blood collected from donors in appropriate physiological conditions.

Animals↗

PubMed1999

The role of plasma proteins and stress in the assessment of hemocompatibility.

The physiological and psychological conditions of subjects supplying blood for hemocompatibility tests significantly affect the behavior of platelets in terms of both adhesion and activation. The responses of platelets to a standard biomaterial, polyethylene (PE), were examined with blood collected from male rabbits both in basal conditions and after stress. Different media were utilized. First, platelet-rich plasma (PRP) was used to obtain a PE response to contact with platelets. Then platelets drawn from PRP were isolated and washed with Krebs-Ringer solution. One aliquot was suspended in serum (Pw-S) where fibrinogen was absent, another aliquot in Krebs-Ringer solution (Pw-KR) (in order to avoid the influence of the plasma proteins on platelets), and a third aliquot in the original plasma from which the platelets were drawn (Pw-PPP) (in order to restore the initial condition of the plasma but with washed platelets). The analysis of platelet adhesion and morphology was performed by Scanning Electron Microscopy (SEM). Differences in platelet adhesion and morphology were observed with four different media in nonstressed animals, with Pw-PPP showing a higher number and Pw-S and PW-KR lower numbers. Platelet morphology indicated low levels of activation. The platelets drawn from stressed subjects could not be counted in either PRP or PPP medium because they were fully aggregated and adhered; in contrast, in Pw-KR and Pw-S, no significant differences were found with respect to nonstressed conditions, and there was little difference in platelet morphology. All of these factors underline the role of plasma proteins, in particular fibrinogen, in the stress-induced activation of platelets.

Animals↗

PubMed1999

Neuroendocrine and behavioral effects of CRH blockade and stress in male rats.

Our previous data have shown that restraint (RT), a mild nonpainful stressor, acutely impairs nonsocial and social behavior in male rats. Corticotropin-releasing hormone (CRH) is a regulator of these behavioral responses. To evaluate whether CRH mediates the neuroendocrine and behavioral alterations present 24 h after restraint stress, we administered the CRH antagonist alpha-helical CRH(9-41) (alpha-hCRH) intracerebroventricularly to male rats and we compared its effects with those of saline. Twenty-four hours after treatment, nonsocial behaviors were significantly decreased by alpha-hCRH, this effect being independent of RT. Among social behaviors, only introductory activity showed significant differences as a result of both RT and alpha-hCRH. The concentrations of ACTH in the plasma and those of beta-endorphin in the anterior and neurointermediate lobes of the pituitary were affected by alpha-hCRH treatment. The effect on ACTH was simply related to the administration of the alpha-hCRH, while for beta-endorphin, significant interactions between alpha-hCRH and RT were found. On the whole, these results point to the role played by CRH in the control of neuronal mechanisms involved in the stress-induced effects.

Adrenocorticotropic Hormone↗

PubMed1999

Effects of formalin pain on hippocampal c-Fos expression in male and female rats.

Immediate early genes are crucial intermediates in a cascade linking membrane stimulation to long-term alterations of neuronal activity. In the present experiment, we performed immunohistochemistry for c-Fos to determine the effects of persistent pain on cells of the hippocampus of male and female rats. Animals were subcutaneously injected with formalin (50 microl, 10%) and perfused: 2 h later, time 2; 24 h later, time 24; 24 h later after 20 min of the open-field test, time 24/OF. Controls were left undisturbed. In control, c-Fos was higher in females than in males in all hippocampal fields. In males at time 2, formalin increased c-Fos in the dentate gyrus (DG) and CA3 fields; at time 24, c-Fos returned to the control level; at time 24/OF, c-Fos was higher than in control in the DG, but not in the other fields. In the formalin-treated females at time 2 and at time 24, c-Fos levels were lower, or tended to be lower, than in control in all hippocampal fields; at time 24/OF, c-Fos levels in the DG were higher than in control and in males. In conclusion, persistent pain had different effects on c-Fos in the hippocampal subfields, depending on the time after treatment and the sex of the subject.

Analysis of Variance↗

PubMed1999

The role of Fbg in platelet adhesion to polymeric materials in conditions of psychological stress.

The effect of psychological stress on platelet adhesion to five polymeric materials (polyurethane, polyurethane filled with BaSO4, polyethyleneterephthalate, silicone and low-density polyethylene) was studied. The platelets were obtained from non-stressed and stressed rabbits as platelet-rich plasma (PRP) and, once washed (Pw), were suspended in different media, i.e. in platelet poor plasma (Pw-PPP), in serum (Pw-S) and in Krebs-Ringer solution (Pw-KR). Scanning electron microscopy of platelet adhesion and morphology revealed differences in the platelet activating power of the various materials. The washing procedure and resuspension in PPP generally resulted in an increased number of adherent platelets, compared with the number of platelets adherent to the same material in PRP. However, platelets washed and suspended in Pw-KR or Pw-S showed the same shape distribution as in PRP. When platelets from stressed rabbits were used, there was very strong aggregation and activation of the platelets in both PRP and Pw-PPP, independent of the chemical nature and surface structure of the material. In contrast, in Pw-KR and Pw-S (in which Fbg is absent) a general picture of single, not very modified platelets was observed. Their number and shapes changed according to the nature of the different materials. On the whole, the present results confirm our original hypothesis of a key role of the psychological condition of the blood donor and strongly indicate Fbg as the determinant factor in the pattern of platelet adhesion.

Animals↗

PubMed1999

Emotional behavior in female rabbits: hippocampal EEG and neuroendocrine aspects.

Behavior, hippocampal electrical activity, plasma hormones and hippocampal choline acetyltransferase (ChAT) were considered in two groups of female rabbits, different in age and condition of breeding, both in the presence and absence of emotional stimuli. In the two groups of female rabbits (4 and 18 months old), permanent electrodes were implanted bilaterally in the two dorsal hippocampi and, one week later, the animals were exposed for three consecutive days to the following tests: Day 1, novel environment (NE); Day 2, object with odor (O); Day 3, sparrow hawk (SP). Behavior: in comparison with Day 1, exploration was decreased by the object and by the sparrow hawk in the older females and increased in the younger ones. Quiet and alert immobility was higher during the SP test, while freezing and pointing were lower in the older females than in the young ones. Electrical activity: peak frequency was lower in younger females than in the older ones. The frequency band distribution corresponding to exploration and immobility showed that in the older females the % of high frequency band increased from the first to the third day of testing, while an opposite trend was present in the younger females. In the case of freezing the hippocampal electric activity showed a more rhythmical component in younger females than in the older ones. Hormones: increased corticosterone levels after the SP test were directly correlated with exploration and inversely correlated with freezing. Dorsal hippocampal ChAT was directly correlated with quiet immobility. These data indicate a relationship between the responses to the anxious/fearful stimuli and the age and/or breeding experience of the female rabbits; this is shown by both the hippocampal electrical activity and the behavioral differences between the two groups.

Animals↗

PubMed1998

Behavioural and hormonal effects of restraint stress and formalin test in male and female rats.

The formalin test was used to measure the analgesia induced by restraint in male and female rats. Animals were restrained for 30 min or left undisturbed in their cage and then (1) killed immediately to collect blood for hormonal determinations; or (2) subcutaneously injected with formalin in the hind paw (or sham-injected), introduced to an open field for recording of behaviour, and killed at the end of this procedure. In both experiments, corticosterone was found to be higher in females. In Experiment 1, the ability of restraint to be stressful was confirmed by the increase in corticosterone in both sexes and by the decrease of testosterone in males. In Experiment 2, restraint-treatment induced a reduction in licking and flexing that was limited to the second phase. The reduction occurred in different periods and to a different degree in the two sexes; it was greater in females. Spontaneous behaviours showed sex differences in restraint-treated but not in formalin-treated animals. The results show that the hormonal effects observed after restraint are not present after the formalin test and that the marked analgesia observed with phasic painful stimuli does not occur with a longer-lasting one such as that induced by formalin, after which only partial and short-lasting effects were observed.

Analysis of Variance↗

PubMed1997

Effects of novelty, pain and stress on hippocampal extracellular acetylcholine levels in male rats.

In vivo microdialysis was used to assess the effects of Novelty, persistent pain (Formalin test) and stress (Restraint) on hippocampal acetylcholine (ACh) release. Experiments were carried out during the dark phase, i.e. during the active period of the animal, and consisted of four experimental phases: Baseline (30 min), Novelty (30 min), Formalin test (90 min) and Restraint (30 min); each animal was consecutively exposed to all phases. The extracellular levels of ACh in the dorsal hippocampus were estimated by measurement of its concentration in the perfusion fluid by high-performance liquid chromatography with electrochemical detection. The introduction to a new environment (Novelty) induced in all rats higher ACh levels than Baseline. Formalin treatment decreased ACh release only in animals considered 'Inactive' during the Novelty phase while no modification in ACh release was observed in the 'Active' ones. Restraint did not produce any modification of ACh release but increased Corticosterone plasma levels both in sham- and formalin-treated animals. Results indicate that Novelty, but not Formalin or Restraint, increases ACh release in the hippocampus and that the type of behavioral state displayed by the animal at the time of formalin injection determines the response of the septo-hippocampal cholinergic pathway.

Acetylcholine↗

PubMed1997

Sex differences in pain-induced effects on the septo-hippocampal system.

In addition to its role in the modulation of functions such as arousal and attention, learning and memory, the limbic system has repeatedly been described to be involved in the regulation of several behavioral aspects concerning the adaptation to aversive situations, including pain. A key role in these processes seems to be played by the septo-hippocampal system. This paper, far from being a comprehensive review of all the data available about the limbic system, describes some of the circuits participating in the septo-hippocampal system, with the aim of contributing to an understanding of the sex differences in the behavioral, hormonal and neuronal responses to aversive stimuli. It will appear that the complex anatomical and functional interactions between the different neurotransmitters acting at this level prevent one from indicating a certain substance as more important than others in determining a difference between the two sexes. This leads to the conclusion that the septo-hippocampal formation in toto plays a key role in determining the sex differences in the 'pain experience'.

Animals↗

PubMed1997

Sex-dependent effects of formalin and restraint on c-Fos expression in the septum and hippocampus of the rat.

In the present study we have demonstrated that the same aversive stimulus induces different patterns of expression of transcription factors in the hippocampus and septum of male and female rats. We have investigated by immunohistochemistry the effects of a persistent painful stimulus and restraint stress on c-Fos expression in the hippocampus and septum of male and female rats. Subjects were randomly assigned to one of three experimental groups: (i) untreated controls, (ii) subcutaneous injection with formalin (50 microliters, 10%) in the right hindpaw, or (iii) immobilization in an adjustable restrainer. Formalin-treated and restrained animals were killed 90 min after the beginning of treatment. In both male and female rats, unilateral injection of formalin induced bilateral c-Fos expression in the hippocampus, but the number of labeled neurons was two-fold higher in females than in males. Restraint stress was not effective in c-Fos induction in the hippocampus of both sexes. In the septum, both treatments increased c-Fos, but this increase tended to be greater in males than females. Previous experiments have consistently shown that male and female rats react differently to aversive stimulation. The present findings suggest that hormonal and behavioral differences between the sexes are accompanied by genetic modifications in those brain areas involved in cognition and emotion.

Animals↗