Release of norepinephrine from the rat's hypothalamus perfused with alcohol: relation to body temperature

The arousal effect of An-Gong-Niu-Huang-Wan on alcoholic-induced coma rats: A research based on EEG

ETHNOPHARMACOLOGICAL RELEVANCE

Acute alcohol intoxication is one of the leading causes of coma. A well-regarded Chinese herbal formula, known as An-Gong-Niu-Huang-Wan (AGNHW), has garnered recognition for its efficacy in treating various brain disorders associated with impaired consciousness, including acute alcohol-induced coma. Despite its clinical effectiveness, the scientific community lacks comprehensive research on the mechanistic aspects of AGNHW's impact on the electroencephalogram (EEG) patterns observed during alcohol-induced coma. Gaining a deeper understanding of AGNHW's mechanism of action in relation to EEG characteristics would hold immense importance, serving as a solid foundation for further advancing its clinical therapeutic application.

AIM OF THE STUDY

The study sought to investigate the impact of AGNHW on EEG activity and sleep EEG patterns in rats with alcoholic-induced coma.

MATERIALS AND METHODS

A rat model of alcohol-induced coma was used to examine the effects of AGNHW on EEG patterns. Male Sprague-Dawley rats were intraperitoneally injected with 32% ethanol to induce a coma, followed by treatment with AGNHW. Wireless electrodes were implanted in the cortex of the rats to obtain EEG signals. Our analysis focused on evaluating alterations in the Rat Coma Scale (RCS), as well as assessing changes in the frequency and distribution of EEG patterns, sleep rhythms, and body temperature subsequent to AGNHW treatment.

RESULTS

The study found a significant increase in the δ-band power ratio, as well as a decrease in RCS scores and β-band power ratio after modeling. AGNHW treatment significantly reduced the δ-band power ratio and increased the β-band power ratio compared to naloxone, suggesting its superior arousal effects. The results also revealed a decrease in the time proportion of WAKE and REM EEG patterns after modeling, accompanied by a significant increase in the time proportion of NREM EEG patterns. Both naloxone and AGNHW effectively counteracted the disordered sleep EEG patterns. Additionally, AGNHW was more effective than naloxone in improving hypothermia caused by acute alcohol poisoning in rats.

CONCLUSION

Our study provides evidence for the arousal effects of AGNHW in alcohol-induced coma rats. It also suggests a potential role for AGNHW in regulating post-comatose sleep rhythm disorders.

Altered behavior and alcohol tolerance in transgenic mice lacking MAO A: a comparison with effects of MAO A inhibitor clorgyline

The influence of deficiency of monoamine oxidase A (MAO A) gene and the lack of enzyme MAO A on the behavior of transgenic mouse strain (Tg8) was studied. It was shown that MAO-A-lacking mice differed from mice of the wild-type strain C3H/HeJ (C3H) by an attenuated acoustic startle response, prepulse inhibition (PPI) was unchanged. In Tg 8 mice, the exploratory nose-poking in the holeboard test as well as exploratory line crossing in the "light-dark" test were decreased. No effect of MAO A deficiency on locomotor activity was found. No alcohol preference or difference between Tg8 and C3H in ethanol consumption in the free-choice test has been found, although an increase in alcohol tolerance has been demonstrated. Ethanol-induced (0.3 g/100 g ip) sleep latency was longer, duration of sleep was shorter and ethanol hypothermia was reduced in MAO-A-lacking mice. Comparison of effects of MAO A knockout with those of irreversible MAO A inhibitor clorgyline (5 and 10 mg/kg ip) on C3H mice showed a similar reducing effect on ethanol-induced sleep, but potentiated ethanol-induced hypothermia. Clorgyline administration provoked a tendency to decrease of exploratory activity in the nose-poking test and decreased the frequency of exploratory rearings in the light-dark test. Clorgyline (5 and 10 mg/kg) did not affect the acoustic startle response, but a dose of 5 mg/kg diminished PPI. Therefore, Tg8 mice exhibited a decreased startle response and exploratory activity and an increased tolerance to ethanol. A similar increase in tolerance to ethanol-induced sleep and a tendency to decrease exploratory behavior were displayed by clorgyline. Other effects on behavior were different, suggesting the influence of long-lasting action of MAO A knockout and the involvement of a compensatory mechanism in Tg8 mice.

Ethanol-induced hypothermia and thermogenesis of brown adipose tissue in the rat

The effects of two ethanol doses (2 and 3 g/kg) on colonic temperature and levels of norepinephrine (NE) and uncoupling protein (UCP) mRNA in the interscapular brown adipose tissue (IBAT) were examined in rats exposed to 20 degrees C or 4 degrees C for 2 h. The controls received 0.9% NaCl solution. Ethanol produced a significant hypothermic effect versus saline at both temperature conditions. The dose at 3 g/kg reduced colonic temperature more in the cold than at room temperature (p < 0.01), whereas the ambient temperature did not affect the decrease in rats that received ethanol 2 g/kg. At room temperature ethanol did not significantly change the levels of NE or UCP mRNA, whereas after cold exposure (4 degrees C) NE levels in the ethanol-treated rats were significantly lower than in the controls (p < 0.001). Ethanol did not prevent a cold-induced increase in the UCP mRNA levels, although it reduced an increase. The magnitude of the reduction in increase was dependent on the dose, being significant at the dose of 3 g/kg (p < 0.05). The results show that the ethanol-induced drop in body temperature is not necessarily related to IBAT thermogenesis, as indicated by the levels of NE and UCP mRNA.

Effects of ethanol injection to the preoptic area on sleep and temperature in rats

Bilateral microinjection of ethanol to the preoptic area of rats causes a dose-dependent hypnotic effect at doses that do not affect brain temperature. Rats were polygraphically recorded for 6 h, and brain temperature was recorded every 10 min for 3 h. Administration of 0.047 mumol ethanol increased total sleep during the 3-6 h interval, while 0.24 and 0.47 mumol ethanol increased deep slow-wave sleep (SWS2) and total sleep during the 3-6- and 0-6-h intervals. The 0.24-mumol ethanol microinjections also increased REM sleep for the 0-6-h interval. No changes in sleep latencies were observed.

Differential actions of RO 15-1788 and diazepam on poikilothermia, motor impairment and sleep produced by ethanol

In adult male Sprague-Dawley rats kept at an ambient temperature of 23-25 degrees C, ethanol was injected intraperitoneally in a dose of 4.0 g/kg to produce a clear-cut impairment of autonomic and motorial functions. Following the injection of ethanol, motor coordination, measured on a rotorod, behavioral sleep, righting reflex and colonic temperature were monitored at predetermined intervals for 5.0-7.0 hr. In the first experiment, either 1.0 mg/kg RO 15-1788 (flumazenil), a benzodiazepine (BZ), receptor antagonist, or 1.0-5.0 mg/kg diazepam, a classical benzodiazepine receptor agonist, were injected intraperitoneally either alone or concurrently with ethanol's administration. In the second study, either RO 15-1788 (1.0 or 2.0 mg/kg) or diazepam (1.0 or 5.0 mg/kg) was injected at the nadir of the fall of body temperature induced by ethanol. Although RO 15-1788 alone failed to affect the rats' temperature, it did not prevent the characteristic ethanol-induced hypothermia but rather potentiated it in a dose-dependent manner. Further, this BZ receptor antagonist exacerbated motor incoordination and other behavioral effects when given either simultaneously with ethanol or at the nadir in the animals' core temperature. Although diazepam evoked a dose-dependent hypothermia, it did not enhance ethanol-induced hypothermia when both drugs were administered simultaneously. However, diazepam augmented motor incoordination and other effects and served to delay their recovery. When given to the rats at the nadir of ethanol hypothermia, diazepam did not potentiate ethanol's thermolysis but retarded the recovery from hypothermia; it caused also a dose-dependent delay in the recovery of motor coordination and other responses.(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of alpha-methyl-p-tyrosine pretreatment on ethanol-induced narcosis and hypothermia, as well as in the development of tolerance to these effects in UChA and UChB rats

We have previously reported that UChA rats (genetically low ethanol consumer) develop tolerance to narcosis time easier than UChB rats (genetically high ethanol consumer). We also have reported that UChA rats develop tolerance to the hypothermic effect of ethanol, while in UChB rats the repeated administration of ethanol induces sensitization towards this effect. In the present paper the effects of alpha-methyl-p-tyrosine (AMPT)--a competitive inhibitor of norepinephrine synthesis--on ethanol-induced narcosis and hypothermia, as well as in the development of tolerance to these effects, were studied in both strains of rats. Results obtained show that AMPT pretreatment induced a significantly higher increase in narcosis time and hypothermia, as well as, greater susceptibility to ethanol toxicity in UChB than UChA rats. Furthermore, the simultaneous treatment with AMPT and ethanol did not change the development of tolerance to narcosis time in both strains and to hypothermia and sensitization in UChA and UChB rats respectively.

Alcohol-induced poikilothermia, sleep and motor impairment: actions on brain of EGTA and verapamil

In the early 1970's, calcium ions were implicated in the mechanism underlying the perturbation of the "set point" for body temperature produced by a thermolytic drug. Since Ca++ is thought to be involved in the incapacitating effects of ethanol on body temperature and motor coordination, this investigation sought to compare the differential central actions of a Ca++ chelating agent with those of a Ca++ channel antagonist on ethanol-induced poikilothermia and motor functions. A chronically indwelling cannula for intracerebroventricular (ICV) injection was implanted stereotaxically in each of 25 adult male Sprague-Dawley rats. Following postoperative recovery, each rat was given ethanol in a 20% v/v solution by the intraperitoneal route in a dose of 4.0 g/kg, which was selected to insure a clear-cut impairment of autonomic and motorial functions. Colonic temperature, behavioral sleep, righting reflex and degree of motor coordination on a rotorod were monitored at selected intervals for 5.0-7.0 hr after the injection of ethanol. Two experimental designs were used: First, either 12.5, 25 or 50 micrograms ethyleneglycol-bis-(beta-amino ethyl ether) N,N'-tetra-acetic acid (EGTA), or 25 or 50 micrograms verapamil, both dissolved in an artificial CSF vehicle, were infused ICV at the same time as ethanol's administration. In the second design, the compounds were infused at the nadir of the ethanol-induced temperature decline. EGTA infused ICV in the rat together with ethanol produced a dose-dependent inhibition of ethanol hypothermia and a more rapid recovery of the animal's righting reflex, arousal and motor coordination than that following ethanol alone. Although verapamil infused ICV in the 50 micrograms but not 25 micrograms dose minimized the poikilothermic response to ethanol, it was not as efficacious as that of EGTA. When infused ICV at the point of maximum fall in the rats' temperature. EGTA entirely reversed the hypothermia induced by ethanol and evoked a thermogenic response in the rat. In contrast, verapamil infused ICV in the same doses tended only to retard the further decline in the animal's body temperature. Similarly EGTA was far more effective than verapamil in ameliorating the other physiological actions of ethanol in terms of the reversal of areflexia, behavioral sleep and motor incoordination. These results suggest that the characteristic attributes of membrane Ca++ in terms of its binding and other neuronal properties play a significant functional role in the incapacitating action of ethanol on the diverse physiological processes mediated by the brain.(ABSTRACT TRUNCATED AT 400 WORDS)

A neuroanatomical substrate for alcohol drinking: identification of tetrahydropapaveroline (THP)-reactive sites in the rat brain

Certain endogenously synthesized adducts, derived from a condensation reaction of a catechol- or indole-amine with a biogenic aldehyde, act in the brain to augment or suppress the drinking of ethyl alcohol. When infused directly into the cerebral ventricles, a tetrahydro-isoquinoline such as tetrahydropapaveroline (THP) can enhance markedly the consumption of alcohol even in noxious concentrations. The present study was undertaken to isolate and identify specific anatomical structures in the limbic-midbrain, limbic-forebrain which mediate the changes in the ingestion of alcohol induced by THP. In adult male Sprague-Dawley rats, a 23 ga guide tube was implanted stereotaxically either unilaterally or bilaterally in cerebral regions extending from coronal planes AP 1.0-10.0. Following recovery, each animal was tested by a standard screen for its self-selection of water versus an alcohol solution offered in 10 concentrations increased on each of 10 days from 3 to 30%. THP was dissolved in an artificial CSF vehicle containing Na2S2O5 or ascorbate and then microinjected in a volume of 1.5-2.0 microliters at a depth 1.0-1.5 mm beneath the tip of the guide. After a set of 5 microinjections of THP in a dose of 25, 50 or 250 ng was given over 3 days, the same 10-day alcohol preference sequence was repeated. In nearly all rats, the microinjection series was repeated at either one or two depths 1.0-1.5 mm ventral to the first, after which the same alcohol test was repeated. The results showed that THP induces or sustains significant increases in alcohol intake when the adduct was injected at 16 sites within caudal AP planes 1.0-5.0. Structures sensitive to THP included the substantia nigra, reticular formation, medial lemniscus, zona incerta and medial forebrain bundle. When injected at 21 sites located more rostrally within AP planes 6.5-10.0, THP also evoked significant increments in alcohol intake of a similar magnitude. The reactive loci included the N. accumbens, olfactory tubercle, lateral septum, preoptic area, stria terminalis, medial forebrain bundle and rostral hippocampus. In terms of the efficacy of the dose of THP microinjected, 25, 50 and 250 ng induced alcohol self-selection in 81%, 5% and 14% of the sites, respectively. Repeated microinjections following identical procedures of two control solutions at 46 homologous sites within corresponding coronal planes from AP 1.5-10.0 produced no significant alterations in g/kg or proportional intakes of alcohol. Composite anatomical maps of the THP-reactive sites revealed their integral overlap with dopaminergic pathways which originate in the ventral tegmentum and substantia nigra and project rostrally to s

Chlorpromazine-induced alterations in hypothalamic amine metabolism and stress responses in severe cold

To investigate the effects on the central nervous system of severe cold stress with and without chlorpromazine, guinea pigs were treated with chlorpromazine or 0.9% NaCl and exposed to -20 degrees C or +23 degrees C for 1 h. Hypothalamic noradrenaline (NA), dopamine (DA), 5-hydroxy-tryptamine (5-HT), 3-methoxy-4-hydroxyphenyl ethylene glycol (MHPG), homovanillinic acid (HVA) and 5-hydroxy-indoleacetic acid (5-HIAA) were determined by high-performance liquid chromatography. Serum, urinary and vitreous fluid catecholamines, muscle and liver glycogen, and blood glucose were also measured. Chlorpromazine caused distinct hypothermia at -20 degrees C and slight hypothermia at +23 degrees C. The rise in hypothalamic MHPG, 5-HIAA and MHPG/NA and in 5-HIAA/5-HT ratios in the cold indicate increased noradrenergic and serotonergic activity. The latter was inhibited by chlorpromazine and a drug-induced inhibition of noradrenergic neurons could not be ruled out. Chlorpromazine increased the turnover of DA at room temperature and the same tendency was seen in the cold. The hypothermic animals had low serum catecholamines, indicating diminished sympathetic activity. The chlorpromazine-treated cold-exposed animals did not react to the environmental stress by sympathetic activation, as urinary NA and adrenaline were not elevated, but DA was excreted by all the drug-treated animals. Vitreous fluid NA and DA were elevated as an indicator of cold stress, and no drug effect was seen in this fluid.

Temperature-related release of serotonin from unrestrained rats' pre-optic area perfused with ethanol

The circumscribed effect of ethyl alcohol on the local efflux of serotonin (5-HT) within the thermosensitive region of the anterior hypothalamic, pre-optic area (AH/POA) of the unrestrained rat was examined in relation to core temperature. A single guide cannula for push-pull perfusion was implanted stereotaxically in the AH/POA within coronal planes AP 7.0-8.2. Following 3-4 push-pull perfusions with control artificial CSF of a site identified as reactive to 5-HT, ethanol in a concentration of 2.75 (471 mM) or 5.5 (942 mM) percent was perfused at the same locus over a 5-10 min interval. Successive samples of perfusate were assayed for their content of 5-HT by high performance liquid chromatography using electrochemical detection (HPLC-EC). Within a circumscribed region of the AH/POA of the rat maintained at an ambient temperature of 22 degrees C, ethanol induced either an immediate or delayed hypothermia of short latency or a transient decline followed by an immediate increase in core temperature. In each case, the shift in temperature depended on the anatomical site of push-pull perfusion. Overall, the fall in core temperature was accompanied by an inhibition in the efflux of 5-HT. However, the consequent rise in the rat's core temperature was associated with an enhanced release of 5-HT in the samples of perfusate collected from the AH/POA. These results suggest that serotonergic synapses within the AH/POA are apparently involved in the thermolytic effects of ethanol as well as in the thermogenesis following the interval of heat loss.

Hypothalamic and serum catecholamines in ethanol and acetaldehyde treated guinea-pigs. Relation to moderate short-term cold exposure

Adult guinea-pigs were treated with ethanol (2.5 g/kg, IP) or acetaldehyde (100 mg/kg, IP) and exposed to moderate cold (+4 degrees C) for 50 minutes. Controls were given 0.9% NaCl solution. The hypothalamic catecholamines norepinephrine (NE) and dopamine (DA) and also norepinephrine and epinephrine (E) in the serum were analyzed by high-performance liquid chromatography with an electrochemical detector. Blood glucose, free fatty acids and glycogen in the liver and skeletal muscle were also measured. Acetaldehyde caused a similar drop in colon temperature as did ethanol, but neither could prevent cold-induced vasoconstriction in the ear lobe. Ethanol significantly reduced the concentration of NE in the hypothalamus compared to the controls. Acetaldehyde had a tendency to lower hypothalamic NE. There was no significant difference between drug-treated groups in NE concentration. Neither ethanol nor acetaldehyde had any effect on hypothalamic DA. In the ethanol group serum E and glucose were significantly elevated compared to the acetaldehyde group. Serum glucose was also higher compared to the controls, and the difference in serum E concentration near the level of significance. No significant differences were found between the groups in serum NE, FFA or skeletal muscle and liver glycogen concentration. The results point to a possible central effect of ethanol during a short-term moderate cold exposure. The effects of acetaldehyde on neuronal tissue remain speculative, but a possible effect on noradrenergic neurons cannot be ruled out. Although the hypothermic effect of acetaldehyde corresponded that of ethanol, further experiments are required to elucidate the role of acetaldehyde in ethanol-induced hypothermia.

Central Ca++-channel blockade reverses ethanol-induced poikilothermia in the rat

Two series of experiments were performed to determine the possible involvement of Ca++ channels in the thermolytic action of ethanol administered at a room temperature of 22 degrees C. In one group of 11 adult female Sprague-Dawley rats, stainless steel guide cannulae were implanted stereotaxically above the lateral cerebral ventricle. Prior to an experiment, a thermistor probe was inserted into the colon so that core temperature could be monitored continuously for up to six hours or until the temperature had returned to a previous baseline level. When the animal's body temperature had stabilized, a dose of 4.0 g/kg in a v/v solution of 20% ethanol was given by intragastric gavage. After the body temperature had declined by about 2.0 degrees C, ordinarily 30 min after ethanol administration, either control CSF or the vehicle plus one of four doses of verapamil (8.3, 25, 50 and 100 micrograms) was infused intracerebroventricularly (ICV) in a volume of 10 microliter. In a second group of 7 unoperated rats, either 4.0 g/kg ethanol or a physiological saline control solution was administered isovolumetrically by intragastric gavage; then, 30 min later, either 3.0 or 10.0 mg/kg verapamil was injected intraperitoneally. At an ambient temperature of 22 degrees C, ethanol gavage produced a significant decline in colonic temperature which was unaffected by physiological saline given by the same route. Although the CSF control vehicle was without effect, verapamil administered ICV attenuated the thermolytic action of ethanol in all doses tested; however, the lowest dose exerted its antagonist effect but with a longer latency. Conversely, when verapamil was given systemically, the hypothermic action of ethanol was significantly potentiated in a dose-dependent manner.(ABSTRACT TRUNCATED AT 250 WORDS)

Monoamine transmitter release induced by tetrahydro-beta-carboline perfused in hippocampus of the unrestrained rat

Guide cannulae for unilateral push-pull perfusion were implanted stereotaxically to rest just dorsal to the hippocampus of the rat. On recovery, a tissue site in the hippocampus was double-labelled with a 1.0 microliter volume of [14C]-5-hydroxytryptamine (5-HT) and [3H]-norepinephrine (NE). Then the site was perfused by means of push-pull cannulae at a rate of 25 microliters/min with an osmotically-balanced CSF. When tetrahydro-beta-carboline (THBC) was added to the CSF perfusate in a concentration of 0.5-5.0 micrograms/125 microliters, the pattern of efflux of both of the monoamines exhibited an increase in release which was either immediate or delayed depending on the concentration and site of the hippocampal perfusion. Further, if the interval of a sequence of repeated perfusions was less than one day, the efflux of either [3H]-NE or [14C]-5-HT was attenuated. The addition of chlordiazepoxide to the CSF perfusate in a dose of 1.6 microgram/1.0 microliter did not affect the resting efflux of either of the monoamines, but did tend to reduce the THBC-induced release. A morphological "mapping" showed that the anatomical sites of perfusion in the hippocampus were homologous to those within which THBC injected locally induces anxiety-like behavior in the rat. Thus, it is envisaged that this beta-carboline serves to alter the behavior of the animal by a differential shift in the synaptic activity of monoamines within neurons of this limbic system structure which is implicated in emotional responses.