The effect of chronic (3-4 weeks), heavy ethanol exposure on neuronal vacuolation in rat peripheral nervous system was studied in male Wistar rats. The rats were force-fed with 25% ethanol 3 times a day, which resulted in blood ethanol levels of 53.1 +/- 18.8 mmol/l, i.e., marked intoxication. In the superior cervical ganglia (SCG), the ethanol exposure increased the proportion of vacuolated neurons c. 13-fold (0.2 +/- 0.0% in the control ganglia, 2.7 +/- 0.6% in the EtOH-ganglia, P < 0.001). A considerable population of vacuolated neurons (VN) was seen in the sensory inferior vagal (nodose) ganglia, and occasional neurons with large cytoplasmic vacuoles in the sensory dorsal root ganglia (DRG) of the EtOH-rats. In the hypogastric ganglia, where VN are regularly found in the adult rat, ethanol exposure did not affect the amount or the appearance of the vacuolated neurons. The number of VN in the SCG decreased significantly between 2 days and 1 week after cessation of the exposure, but did not return to control level by 1 month after ethanol withdrawal. In electron microscopy, most of the vacuolated SCG neurons showed normal ultrastructure, apart from the large cytoplasmic vacuoles. Some vacuolated neurons, however, showed neuropathologic changes, e.g., dilated endoplasmic reticulum, mitochondrial alterations and increased numbers of myelin figures. These degenerative changes were more frequent in the vacuolated DRG neurons than in the sympathetic ones. The occurrence of VN in rat peripheral ganglia may represent a reaction to increased stimulation during prolonged ethanol exposure and, especially, during repeated phases of ethanol withdrawal.

Animals↗

PubMedDate not supplied

Sympathetic neurons outlive the original host after transplantation to the rat submandibular gland.

Sympathetic ganglion tissue of aged (36 months) Wistar rats was allotransplanted into the submandibular gland (SMG) of young (3 months) animals to study whether sympathetic neurons can outlive the original host. The viability of the transplants was evaluated one year postgrafting, using the formaldehyde-induced fluorescence technique (FIF) for histochemical demonstration of catecholamines, tyrosine hydroxylase (TH) immunohistochemistry, and morphometry. One year after transplantation, grafted superior cervical ganglion (SCG) cells demonstrated catecholamine fluorescence and tyrosine hydroxylase immunoreactivity. The transplants consisted of groups of sympathetic neurons dispersed in a fibrous matrix. After long postgrafting time, the sympathetic neurons of aged rats showed several signs of enhanced degeneration; increased autofluorescent lipopigment, decreased neuronal density and reduced catecholamine fluorescence. The mean diameter of the transplanted aged neurons was significantly decreased. The histograms of grouped diameter values showed a shift to smaller cells in ganglion transplants. A subpopulation of small and medium-sized grafted neurons sent out fluorescent fibers, which were located in a fibrous scar area but did not extend into submandibular host tissue. The results indicate that a long postgrafting time induced degeneration which is comparable to normal aging changes in grafted very old neurons. Thus, aged sympathetic neurons maintain plasticity to survive as transplants, and under favourable conditions these neurons outlive the original host.

Animals↗

PubMedDate not supplied

Reactions of rat sympathetic neurons to ethanol exposure are age-dependent.

Age-differences in the sensitivity of peripheral sympathetic neurons to chronic ethanol exposure and ethanol withdrawal were studied in male Wistar rats aged 4 months, 12 months, or 24 to 25 months. The superior cervical ganglia (SCG) of the young (4 months) and the 2-year-old rats responded to a 12-day or 4-week ethanol exposure with significantly increased catecholamine turnover, while the ganglia of the middle-aged rats (12 months) showed only a minor increase in the intensity of catecholamine fluorescence and tyrosine hydroxylase immunoreactivity. Extensive neuronal vacuolation was found in the 4 months ethanol-exposed SCG, probably as a reaction of a subpopulation of neurons to increased stimulation. Ethanol-induced neuronal loss was most prominent in the SCG of the oldest age group. Contrary to the marked changes in SCG functional and morphometric parameters, the pelvic sympathetic neurons in the hypogastric ganglion showed no significant changes after ethanol exposure. The pattern of ethanol-induced morphological alterations found in the present study did not provide unambiquous support for either the "accelerated aging" or the "increased vulnerability" concept regarding ethanol-aging interactions in the nervous system.

Aging↗

PubMedDate not supplied

Prevention of ethanol-induced sympathetic overactivity and degeneration by dexmedetomidine.

The effects of dexmedetomidine, a selective alpha 2-adrenoceptor agonist, on rat sympathetic neurons were studied during a 12-day, heavy ethanol exposure. Adult male Wistar rats were given ethanol or isocaloric sucrose three times a day by intragastric intubation. Both acute (a single dose of 300 micrograms/kg p.o.) and chronic (100 micrograms/kg x 2 P.O. throughout the experiment) effects of dexmedetomidine were tested. The superior cervical ganglia (SCG) of the ethanol-exposed, non-dexmedetomidine-treated rats showed an abnormally high overall level of tyrosine hydroxylase immunoreactivity (TH-IR) and catecholamine histofluorescence. However, a subpopulation of neurons had apparently lost their catecholamine synthetic activity, as they exhibited no TH-IR or catecholamine fluorescence. The ethanol-exposed ganglia also showed structural alterations (e.g., decreased neuronal size and increased occurrence of vacuolated neurons). In the ethanol-exposed, chronically dexmedetomidine-treated group, by contrast, the SCG exhibited TH-IR and catecholamine fluorescence intensities comparable to those seen in the control ganglia. All the structural parameters studied, as well, were at the control level in the chronically dexmedetomidine-treated group. The single dose of dexmedetomidine offered only marginal protection against the ethanol-induced alterations. These results suggest that chronic dexmedetomidine treatment may prevent ethanol-induced overactivity and degeneration of catecholaminergic neurons.

Adrenergic alpha-Agonists↗

PubMedDate not supplied

Dexmedetomidine alleviates ethanol withdrawal symptoms in the rat.

The effect of dexmedetomidine, a selective alpha 2-adrenoceptor agonist, on ethanol withdrawal symptoms was studied in chronically ethanol-fed rats. After a 4-day ethanol intoxication period the rats were given s.c. injections of dexmedetomidine (3, 10, or 30 micrograms/kg) or saline (control group) at 10, 16, 22, and 39 h after the last dose of ethanol. The severity of ethanol withdrawal symptoms (rigidity, tremor, irritability, hypoactivity) was rated up to 58 h, blind to the treatments. The results showed that dexmedetomidine at doses 10 and 30 micrograms/kg significantly diminished the severity of the ethanol withdrawal reaction as measured by the sum score of the three most specific withdrawal signs (rigidity, tremor, and irritability). Dexmedetomidine at 10 micrograms/kg was the most effective dose, especially in the latter half of the withdrawal period (23-58 h after last dose of ethanol). The results suggest that dexmedetomidine in the treatment of ethanol withdrawal symptoms should be further studied.

Adrenergic alpha-Agonists↗

PubMedDate not supplied

Effects of ageing and intermittent ethanol exposure on rat locus coeruleus and ethanol-withdrawal symptoms.

In this study, the effects of ethanol and age on the morphology of the locus coeruleus (LC) and on the severity of ethanol-withdrawal symptoms were studied during a 5-week intermittent ethanol exposure. Young (3-4 months) and old (29-30 months) male Wistar rats were given highly intoxicating doses of ethanol by intragastric intubations for 4 days, followed by a 3-day ethanol-withdrawal period. This 7-day cycle of ethanol exposure and withdrawal was repeated five times. A non-treated group and a sucrose-fed group of both ages were used as control groups. The severity of ethanol-withdrawal symptoms (rigidity, tremor, irritability, hypoactivity) was rated up to 62 h after the last dose of ethanol. The intoxication level was higher in the old, compared with the young, rats, despite the smaller doses of ethanol given to the old animals. There was no significant difference between the age groups in the severity of the ethanol-withdrawal syndrome. The LC quantitative studies were performed using unbiased stereological methods. The results showed that there was no difference between the age groups in the LC total neuron numbers of the non-treated control groups. The 5-week intermittent ethanol exposure significantly reduced the LC neuron numbers and LC neuronal density in the old ethanol-exposed animals, compared with the sucrose-fed control animals. In the young rats, the ethanol-induced neuron loss did not reach statistical significance. According to the ANCOVA, the difference in the ethanol-induced LC neuronal loss between the age groups may be due to the difference in the intoxication levels. Interestingly, the sucrose intubations were also found to decrease the LC neuronal numbers in the young rats, compared with the non-treated young control group. It was concluded that ageing did not significantly affect the severity of ethanol-withdrawal symptoms or ethanol-induced loss of LC neurons in Wistar rats.

Age Factors↗

PubMedDate not supplied

Evidence of acetaldehyde-protein adduct formation in rat brain after lifelong consumption of ethanol.

Acetaldehyde, the first metabolite of ethanol, has been shown to be capable of binding covalently to liver proteins in vivo, which may be responsible for a variety of toxic effects of ethanol. Acetaldehyde-protein adducts have previously been detected in the liver of patients and experimental animals with alcoholic liver disease. Although a role for acetaldehyde as a possible mediator of ethanol-induced neurotoxicity has also been previously suggested, the formation of protein-acetaldehyde adducts in brain has not been examined. This study was designed to examine the occurrence of acetaldehyde-protein adducts in rat brain after lifelong ethanol exposure. A total of 27 male rats from the alcohol-preferring (AA) and alcohol-avoiding (ANA) lines were used. Four ANA rats and five AA rats were fed 10-12% (v/v) ethanol for 21 months. Both young (n = 10) and old (n = 8) rats receiving water were used as controls. Samples from frontal cortex, cerebellum and liver were processed for immunohistochemical detection of acetaldehyde adducts. In four (two ANA, two AA rats) of the nine ethanol-exposed rats, weak or moderate positive reactions for acetaldehyde adducts could be detected both in the frontal cortex and cerebellum, whereas no such immunostaining was found in the remaining five ethanol-treated rats or in the control rats. The positive reaction was localized to the white matter and some large neurons in layers 4 and 5 of the frontal cortex, and to the molecular layer of the cerebellum. Interestingly, the strongest positive reactions were found among the ANA rats, which are known to display high acetaldehyde levels during ethanol oxidation. We suggest that acetaldehyde may be involved in ethanol-induced neurotoxicity in vivo through formation of adducts with brain proteins and macromolecules.

Acetaldehyde↗

PubMedDate not supplied

Effects of lifelong ethanol consumption on rat locus coeruleus.

The effects of lifelong ethanol consumption and ageing on the morphology of locus coeruleus (LC) were studied in alcohol-preferring AA (Alko Alcohol) rats of both sexes. Ethanol (12% v/v) was the only available liquid for the ethanol-consuming rats from 3 months up to 24 months of age. Young (3-month-old) and old (24-month-old) control groups were included in the measurements. The LC morphometry was performed by an unbiased disector method. In the old control rats, the total neuron number, neuronal density and the volume of the LC proper did not differ from the young controls. In the ethanol-exposed rats, the total neuron number of the LC was decreased by 30% and the LC neuronal density by 22%, compared to the age-matched controls. No gender difference was found in the vulnerability of LC neurons to ethanol-induced degeneration. The results suggest a remarkable sensitivity of the LC neurons to the ethanol-induced degeneration in both male and female rats. The possible mechanisms and functional implications of this neuronal loss are discussed.

Aging↗

PubMedDate not supplied

Transplanted sympathetic neurons from old rats survive in the anterior eye chamber: a histochemical and electron microscopic study.

The purpose of this study was to investigate the viability and ultrastructural characteristics of intraocular superior cervical ganglion (SCG) grafts from young (3 months), aged (24 months) and very old (36 months) rats after short-term (1 month) grafting. The formaldehyde-induced fluorescence (FIF) technique for histochemical demonstration of catecholamines was used to indicate the functionality of transplanted neurons. Ultrastructural changes in grafts were demonstrated by electron microscopy. Four weeks after transplantation, catecholamine histofluorescence in young transplants was almost as strong as in the intact ganglia, while aged and very old grafts showed decreased fluorescence and contained a marked accumulation of autofluorescent lipopigment bodies. Catecholamine histofluorescence showed a decrease in neuronal density of 47%, 59% and 68% in young, aged and very old grafted ganglia, respectively. The shape of most of the transplanted neurons did not differ from that in the intact ganglia, but the average diameter of neurons was decreased after grafting. In electron microscopy, both neurons with normal in vivo fine structure and neurons showing some abnormal cytological alterations were seen in each age group of the transplants. The most prominent feature after grafting was the accumulation of different types of lipopigment bodies in the perikarya of neurons. the organization of the rough endoplasmic reticulum was more irregular in transplanted neurons than in intact neurons. In addition, the amount of neurofilament aggregates increased and some mitochondria were swollen in neurons after transplantation. These results suggest that young sympathetic ganglion tissue survives rather well after transplantation into the anterior eye chamber, while in the aged sympathetic ganglion implants the survival rate is poorer. However, aged and very old SCG grafts were shown to contain and continue to produce noradrenaline, indicating that sympathetic neurons maintain their plasticity and regenerative ability in advanced age. Catecholamine histofluorescence and fine structural changes in the cell structure of grafted sympathetic neurons may indicate an accelerated aging process induced by the transplantation procedure.

Aging↗