Opioidergic mechanisms are not involved in the antihyperalgesic effects of carbamazepine and oxcarbazepine.

The mechanisms of the analgesic action of carbamazepine and oxcarbazepine, in particular the role of opioid receptors, have not been established precisely. The systemic effects of naloxone, an opioid receptor antagonist, on the antihyperalgesic effects of carbamazepine and oxcarbazepine were examined in the model of inflammatory hyperalgesia induced by the intraplantar (i.pl.) administration of concanavaline A (Con A, 0.8 mg/paw) into the rat hind paw. Naloxone (3 mg/kg; i.p.) did not alter the antihyperalgesic effects of either carbamazepine or oxcarbazepine. These results indicate that the opioid system of pain modulation does not play a significant role in the antihyperalgesic effects of carbamazepine and oxcarbazepine.

Role of alpha2-adrenoceptors in the local peripheral antinociception by carbamazepine in a rat model of inflammatory mechanical hyperalgesia.

The anticonvulsant carbamazepine was recently shown to possess local peripheral antinociceptive properties. In this study, we investigated whether alpha2-adrenergic receptors are involved in the local peripheral antihyperalgesic effects of carbamazepine and determined the type of interaction between carbamazepine and clonidine, an alpha2-adrenoceptor agonist. Intraplantar (i.pl.) coadministration of either carbamazepine (100-1000 nmol/paw) or clonidine (1.9-3.7 nmol/paw) with the proinflammatory compound concanavalin A (Con A; 0.8 mg/paw) caused a significant dose- and time-dependent reduction of the difference between the forces exerted by a rat's hind paws in a modified paw-pressure test. The coadministration of 260 and 520 nmol/paw (i.pl.) yohimbine, an alpha2-adrenoceptor antagonist, with carbamazepine, significantly depressed the local antihyperalgesic effect in a dose- and time-dependent manner whereas yohimbine by itself did not have any effect. The administration of a mixture of carbamazepine and clonidine at fixed dose fractions (1/4, 1/2 and 3/4) of ED50 caused a significant and dose-dependent reduction of Con A-induced hyperalgesia. Isobolographic analysis revealed an additive interaction. These results suggest that alpha2-adrenoceptors play a role in the local peripheral antihyperalgesic effects of carbamazepine and that local peripheral coadministration of carbamazepine with clonidine results in an additive antihyperalgesic effect.

Peripheral anti-hyperalgesia by oxcarbazepine: involvement of adenosine A1 receptors.

In this study we determined whether oxcarbazepine (OXC) could produce local peripheral antinociceptive effects in a rat model of inflammatory hyperalgesia, and whether adenosine receptors were involved. When coadministered with the pro-inflammatory compound concanavalin A, OXC (1000-3000 nmol/paw) caused a significant dose- and time-dependent anti-hyperalgesia. Caffeine (1000-1500 nmol/paw), a nonselective adenosine receptor antagonist, as well as 1,3-dipropyl-8-cyclopentylxanthine (DPCPX) (10-30 nmol/paw), a selective A1 receptor antagonist, coadministered with OXC, significantly depressed its anti-hyperalgesic effect. Drugs injected into the contralateral hind paw did not produce significant effects. These results indicate that OXC produces local peripheral anti-hyperalgesic effects, which is mediated via peripheral A1 receptors.

The treatment of delayed polyneuropathy induced by diisopropylfluorophosphate in hens.

This study was undertaken to examine the influence of atropine, oximes and benzodiazepine on organophosphate-induced delayed polyneuropathy (OPIDP) in hens, which were poisoned with diisopropylfluorophosphate (DFP). The birds were treated with a standard neuropathic dose of DFP (1.1 mg/kg, s.c.), which produced typical signs of OPIDP. The development of OPIDP was observed within the followings 22 days. All drugs were given subcutaneously (s.c.), intramuscularly (i.m.) or intraperitoneally (i.p.), 20 min before the poison. The results obtained have shown that atropine (20 mg/kg, i.p.) only in combination with oxime TMB-4 (15 mg/kg, i.m.) produced significant improvement of OPIDP symptoms in comparison with positive control. Clinical signs and symptoms of OPIDP in the group which was treated with atropine (20 mg/kg, i.p.), TMB-4 (15 mg/kg, i.m.) and midazolam (2.5 mg/kg, i.m.) were more improved than that in the presence of a combination of atropine and TMB-4. The results of these experiments have shown that it is possible to prevent the development of DFP-induced OPIDP in hens by treatment with atropine and TMB-4 or atropine, TMB-4 and midazolam when given before DFP.

Castration of sexually immature rats affects sympathetic innervation of the adult thymus.

It has been hypothesized that maturational processes within the hypothalamo-pituitary-gonadal (HPG) axis and thymus are reciprocally regulated via neural pathways. To test this hypothesis, in the thymi of adult rats orchidectomized (ORX) at age of 1 (ORX-1), 7 (ORX-7) and 30 days (ORX-30): (i) noradrenaline (NA), dopamine (DA) and serotonin (5-HT) contents and acetylcholinesterase (AChE) activity were measured and (ii) the distribution of monoamine- and AChE-containing nerves and cells was examined by a sucrose phosphate glyoxylic acid (SPG) method and enzyme histochemistry, respectively. In all groups of ORX rats, the thymus weight was significantly increased over that in sham-ORX control rats. In the ORX-1 rats, the increase in the thymus weight was accompanied by a proportional increase in the content of both catecholamines and 5-HT; consequently the concentration of each of them remained unaltered. In these animals, the density of both SPG-stained thymus nerve fibers and cells also remained unchanged. In the ORX-7 rats, the rise in the thymus weight was followed by a proportional increase in the content of all monoamines, except for NA which was reduced. Therefore, in these rats neither the thymus concentrations of DA nor that of 5-HT differed from controls, while the concentration of NA was significantly decreased. The reduction in both NA content and concentration reflected a diminished density of SPG-positive nerve profiles. In the ORX-30 rats, the increase in thymus weight was neither paralleled by a proportional increase in the DA content nor in 5-HT, while the content of NA was decreased. Thus, in their thymi the concentration of both NA and DA, as well as that of 5-HT, were significantly reduced. In parallel with these changes, a decreased density of thymic SPG-positive nerve fibers and cells was found. In all ORX rats, the pattern of intrathymic distribution of SPG-positive fibers and cells remained unchanged. Orchidectomy affected neither the activity of AChE (expressed per gram of tissue) nor the density of AChE-positive nerves and cells in the thymus. As the changes in the density of adrenergic nerve fibers in the thymus from ORX rats were not followed by similar alterations in the density of AChE-containing nerve fibers, it does not seem likely that NA and AChE are colocalized in the thymus nerve fibers. The results also suggest that there is a critical period during ontogenesis when changes within the HPG axis evoked by orchidectomy can affect the sympathetic nerve input to the rat thymus and therefore, most likely, development and function of the organ.

Orchidectomy affects the innervation of the rat thymus.

To assess a putative role of the neural pathways in transfer of information from the gonads to the thymus, adult AO rats were orchidectomized (ORX) or sham ORX (controls); sacrificed 1, 3, 7, or 15 days later and their thymi were analyzed for: (a) the concentrations of noradrenaline (NA), dopamine (DA) and serotonin (5-HT) and distribution of monoamine-containing nerve profiles and (b) the acetylcholinesterase (AChE) activity and distribution of AChE-containing nerve profiles. Three days after the castration, an elevation in the level of both catecholamines, reflecting an increase in the overall intensity of nerve fibers autofluorescence, was found. Seven days post castration neither NA nor DA concentration differed from the appropriate control values, while 15 days after the surgery the concentration of NA was lower than that in the controls, most likely, due to diminished density of noradrenergic nerve profiles. In both the rats sacrificed 7 and 15 days after orchidectomy the concentration of 5-HT was reduced as result of a decrease in the density of 5-HT-containing autofluorescent cells. The activity of AChE was depressed one day after the surgery; then increased, so that 3 days post castration its value was higher than that in the sham ORX. After this increase, AChE activity decreased being, at postoperative day 7 and 15, lower than that in the controls. It seems that this decrease in AChE activity reflected, not only a reduction in the density of AChE-containing nerve fibers, but also a decrease in the density of AChE positive cells. Thus, the results indicate that orchidectomy can evoke changes in the T-cell maturation altering modulatory influences on this process coming via neural route, as well as those coming from the mast cells and AChE positive epithelial cells which constitute important component of the thymus microenvironment.

The influence of dexamethasone treatment of pregnant rats on the development of chromaffin tissue in their offspring during the fetal and neonatal period.

The aim of these examinations was to determine the influence of dexamethasone (Dx)-treatment of gravid females, on day 16 of gestation on the development of medullary chromaffin tissue of their fetuses and neonatal offspring. In conducting these investigations we used stereological as well as spectrofluorimetric measurements, in 20-day-old fetuses and 1-, 3-, 5-, 7-, 9-, 11-, 13- and 14-day-old neonatal rats. Single Dx-treatment (1.5 mg/kg bw) of the dams led to a significant decrease in body and adrenal weight of their fetuses and neonatal offspring, and also reduction of the medullary volume and the number of chromaffin cells during the entire period examined as a result of decreased cell proliferation in the fetal and early neonatal period (till the 5th day of age). The proliferative activity of the chromaffin cells was evaluated through the mitotic index after applying the cytostatic vincristine-sulphate. During the second neonatal week the mitotic index showed significantly higher values in comparison with the corresponding controls, which indicates that there is regeneration and recovery of the adrenal gland medulla. Adrenaline content in the adrenal gland tissue of offspring of Dx-treated dams was significantly reduced only on the 1st neonatal day. Thus, the change in blood glucocorticoid level of pregnant females after a single Dx injection during the period critical for development of the hypothalamo-pituitary-adrenal system in fetuses affects the development and kinetics of medullar chromaffin cell division.

Humoral and cell-mediated immune responses following lesions of the nucleus basalis magnocellularis in the rat.

The present study was undertaken to elucidate whether electrolytic lesions of nucleus basalis magnocellularis--NBM (an animal model of Alzheimer's disease--AD) may influence humoral and cellular immune responses in adult male Wistar rats. For this purpose intact control (IC), sham-operated (SO) and NBM-lesioned rats were divided into two main groups: (1) rats immunized with sheep red blood cells (SRBC) for plaque-forming cell (PFC) response and anti-SRBC agglutinins, and (2) rats immunized with bovine serum albumin in complete Freund's adjuvant (BSA-CFA) for anti-BSA antibody production, Arthus and delayed hypersensitivity skin reaction to BSA. PFC responses and anti-SRBC agglutinins as well as diameter and expression of edema/induration of Arthus/delayed skin reaction and titer of anti-BSA antibody were significantly lower in NBM lesioned rats (compared to IC and SO). The results showed that in NBM-lesioned rats both the humoral and cellular immune responses were suppressed.

Altered gonadal hormone level and constant light-induced stress interfere with the response of the adrenal medulla to oxytocin.

The effect of oxytocin (0.25 IU/100 g per day) on the adrenal medulla was examined in intact, intact estrogen-treated, castrated and castrated testosterone-treated adult male Wistar rats. Stereological analysis of the gland (N = 5 rats per group) revealed that in intact animals the number of chromaffin cells (x10(3)) was significantly increased after 3-day (saline: 467.6 +/- 27.4; oxytocin: 567.6 +/- 28.9) or 7-day (saline: 486.2 +/- 39.1; oxytocin: 618.7 +/- 36.8) oxytocin administration. During 7 days of recovery after the 7-day treatment, the chromaffin cell number returned to the control level (saline: 491.4 +/- 12.6; oxytocin: 554.4 +/- 28.7). The effect of oxytocin on chromaffin cell number was also observed in rats simultaneously injected with estradiol (0.3 micrograms/100 g per day) for 10 days (estradiol: 454.3 +/- 32.8; estradiol+oxytocin: 576.1 +/- 25.0), as well as in 10-day castrated rats (saline: 594.7 +/- 22.7; oxytocin: 765.3 +/- 33.1). Testosterone replacement (0.6 mg/100 g per day) abolished the medullary response to oxytocin (testosterone+saline: 528.5 +/- 24.7; testosterone+oxytocin: 620.8 +/- 56.0). There was a 20% rise in adrenal dopamine content (from 0.236 +/- 0.015 to 0.283 +/- 0.015 microgram per pair of glands; N = 9-12) in intact rats injected with oxytocin for 3 days. Oxytocin had no effect on any of the catecholamine levels in adrenal glands of rats exposed to stress induced by constant lighting. The present data indicate that the proliferative response of chromaffin tissue to oxytocin depends on the gonadal hormone level and the basal activity of the adrenal medulla.

Altered gonodal hormone level and constant light-induced stress interfere with the response of the adrenal medulla to oxytocin

The effect of oxytocin (0.25 IU/100 g per day) on the adrenal medulla was examined in intact, intact estrogen-treated, castrated and castrated testosterone-treated adult male Wistar rats. Stereological analysis of the gland (N = 5 rats per group) revealed that in intact animals the number of chromaffin cells (x10(3)) was significantly increased after 3-day (saline: 467.6 +/- 27.4; oxytocin: 567.6 +/- 28.9) or 7-day (saline: 486.2 +/- 39.1; oxytocin: 618.7 +/- 36.8) oxytocin administration. During 7 days of recovery after the 7-day treatment, the chromaffin cell number returned to the control level (saline: 491.4 +/- 12.6; oxytocin: 554.4 +/- 28.7). The effect of oxytocin on chromaffin cell number was also observed in rats simultaneously injected with estradiol (0.3 microg/100 g per day) for 10 days (estradiol: 454.3 +/- 32.8; estradiol + oxytocin: 576.1 +/- 25.0), as well as in 10-day castrated rats (saline: 594.7 +/- 22.7; oxytocin: 765.3 +/- 33.1). Testosterone replacement (0.6 mg/100 g per day) abolished the medullary response to oxytocin (testosterone + saline: 528.5 +/- 24.7; testosterone + oxytocin: 620.8 +/- 56.0). There was a 20 percent rise in adrenal dopamine content (from 0.236 +/- 0.015 to 0.283 +/- 0.015 microg per pair of glands; N = 9-12) in intact rats injected with oxytocin for 3 days. Oxytocin had no effect on any of the catecholamine levels in adrenal glands of rats exposed to stress induced by constant lighting. The present data indicate that the proliferative response of chromaffin tissue to oxytocin depends on the gonadal hormone level and the basal activity of the adrenal medulla.

Relationships between monoaminergic and cholinergic innervation of the rat thymus during aging.

The present study has been undertaken in order to investigate whether aging is accompanied by alterations in the thymic autonomic innervation. The results showed that in aged rats compared to young adult rats the density of monoaminergic histofluorescent nerve profiles decreased remarkably, while their pattern of intrathymic distribution remained unchanged. The thymic concentrations of noradrenaline (NA) and dopamine (DA) also significantly decreased between the age of 12 and 18 months. However, the density of thymic autofluorescent cells (afc) markedly increased over the same period, as well as the concentration of 5-hydroxytryptamine (5-HT). The aged rat thymus seemed to be able to maintain its cholinergic innervation in terms of density and pattern of distribution, while the density of cells with intracytoplasmic acetylcholinesterase (AChE) staining even increased. The neurochemical measurement showed an increase in the activity of AChE between the age of 9 to 18 months. The results indicate an altered relation between the components of thymic autonomic innervation of aged rats that might be related to the reduced immunocompetence of their T cells.

Parasympathetic innervation of the rat thymus during first life period: histochemical and biochemical study.

In the present study we analyzed development of the rat thymus parasympathetic innervation using histochemical determination of distribution and density of acetylcholinesterase (AChE) positive nerve profiles, as well as biochemical measuring of the activity of this enzyme. Rat thymuses from late embryonal to adult periods of life were analyzed. The AChE-positive nerve profiles were found, for the first time, on day 18 of fetal life in capsule and interlobulary septae, but also in the subcapsulary and cortico-medullary areas. The density of these profiles increased during the thymic development. The AChE positive nerve profiles in subcapsulary region were observed mainly in close proximity to the thymic epithelial cells, while in the cortico-medullary region they were found in apposition to the thymocytes. The biochemical analysis showed that the specific AChE activity in rat thymus was high on day 19 of gestation. A significant increase in the activity of this enzyme was measured by the third day of postnatal development, and its activity remained approximately at the same level up to the day 90. The present results suggest that thymus receives parasympathetic innervation relatively early in ontogeny; in addition, these nerve fibers could be involved in the regulation of the organ activity, at least, through action upon the thymocytes and/or by modulation of the thymic epithelial cell activity.

Components of sympathetic innervation of the rat thymus during late fetal and postnatal development: histofluorescence and biochemical study. Sympathetic innervation of the rat thymus.

This study was performed in order to investigate development of sympathetic innervation in the rat thymus. To achieve this aim histofluorescence and biochemical methods were used. The histofluorescence method revealed the presence of sympathetic nervous profiles in this organ for the first time on day 18 of gestation. The density of these profiles and intensity of their fluorescence increased progressively during late embryonal and postnatal development of the organ. In the outer cortex of adult thymus the sympathetic nervous profiles were found mainly in apposition to thymocytes, while in deeper cortex and medulla they were revealed adjacent to thymic epithelial cells. These nervous profiles were also found in close association with thymic autofluorescent cells, which density increased during the thymic postnatal development. Using the fluorometric method the concentrations of neither noradrenaline (NA) and dopamine (DA) nor serotonin (5-HT) were measurable until day 19 of embryogenesis. Their content increased during the postnatal development. The patterns of NA and DA increase during the postnatal development were almost identical, while the pattern of 5-HT increase was quite different. The present results indicate that DA might also be one of the transmitters of the thymic sympathetic nerve supply, as well as that the transmitters of that system can be involved in the regulation of activity of thymic epithelial and autofluorescent cells, but also in the modulation of T cell maturation.

The response of rat adrenal medulla to oxytocin.

Effects of oxytocin (OT) on the adrenal chromaffin tissue of male rats were examined by coupled morphometric and biochemical techniques. Synthetic OT was administered in doses of 0.14 and 0.25 IU/100 g/d during 7 or 10 consecutive days and the effects were followed 1, 24, 72 and 168 hours after the last injection. The function and structure of chromaffin cells were affected by the higher dose of OT only. They caused divergent responses on their amine contents. Adrenaline, noradrenaline and dopamine contents were increased, while serotonin content was decreased. These changes were different in duration and time of incidence. Stereological analysis showed an enhanced number of chromaffin cells and an increase in their total volume. The parallelism between the changes in chromaffin cell number and the catecholamine content strongly suggests a mitogenic effect of the applied OT.