Effect of acute ethanol administration on noradrenaline metabolism in brain regions of stressed and nonstressed rats

Neuroprotective potential of ocimum sanctum (Linn) leaf extract in preventing and attenuating stress induced substantia nigral neuronal damage in rats

BACKGROUND

In Ayurveda; an Indian system of traditional medicine, Ocimum sanctum is said to have remedial effect on hriddaurbalya (problems affecting the mind), aakshepayukta vikara (nervous disorders) and shiroroga (diseases of head). Hence, in Ayurvedic practice, it is profoundly used as an antistress medicine. Stress is known to affect neurons of functionally significant brain regions like substantia nigra. However, experimental evidence showing its effect on morphology of substantia nigral neurons is lacking. In addition, whether the O. sanctum treatment attenuates stress induced substantia nigral neuronal structural changes is not known.

OBJECTIVES

To know the effect of stress on morphology of substantia nigral neurons and the effect of O. sanctum fresh leaf extract (OSE) on substantia nigral neurons of stressed rats.

MATERIAL AND METHODS

Present study included three experiments. Experiment I: To study the effect of 3 and 6 weeks of foot shock stress in rats; Experiment II- To study the effect of 3 weeks of OSE treatment on 3 week-stress undergoing rats and on 3 week-stressed rats; Experiment III- To study the effect of 6 weeks of OSE treatment in 6 week-stress undergoing rats and in 6 week-stressed rats.

RESULTS

In experiment I, stress had significant deleterious effect on dendritic arborization of substantia nigral neurons. Experiments II and III showed prevention and attenuation of the stress induced dendritic atrophy of substantia nigral neurons in both 2 ml and 4 ml OSE treatment groups. Protective effect of OSE was more pronounced in rats which are treated for a longer duration.

CONCLUSIONS

Foot shock stress induces neuronal damage in the substantia nigra of rats. Treatment with fresh leaf extract of O. sanctum could prevent and attenuate the foot shock stress induced behavioral deficit and substantia nigral neuronal damage.

The antihypertensive drug pindolol attenuates long-term but not short-term binge-like ethanol consumption in mice

Alcohol dependence is a debilitating disorder with current therapies displaying limited efficacy and/or compliance. Consequently, there is a critical need for improved pharmacotherapeutic strategies to manage alcohol use disorders (AUDs). Previous studies have shown that the development of alcohol dependence involves repeated cycles of binge-like ethanol intake and abstinence. Therefore, we used a model of binge-ethanol consumption (drinking-in-the-dark) in mice to test the effects of compounds known to modify the activity of neurotransmitters implicated in alcohol addiction. From this, we have identified the FDA-approved antihypertensive drug pindolol, as a potential candidate for the management of AUDs. We show that the efficacy of pindolol to reduce ethanol consumption is enhanced following long-term (12 weeks) binge-ethanol intake, compared with short-term (4 weeks) intake. Furthermore, pindolol had no effect on locomotor activity or consumption of the natural reward sucrose. Because pindolol acts as a dual beta-adrenergic antagonist and 5-HT_1A/1B partial agonist, we examined its effect on spontaneous synaptic activity in the basolateral amygdala (BLA), a brain region densely innervated by serotonin and norepinephrine-containing fibres. Pindolol increased spontaneous excitatory post-synaptic current frequency of BLA principal neurons from long-term ethanol-consuming mice but not naïve mice. Additionally, this effect was blocked by the 5-HT_1A/1B receptor antagonist methiothepin, suggesting that altered serotonergic activity in the BLA may contribute to the efficacy of pindolol to reduce ethanol intake following long-term exposure. Although further mechanistic investigations are required, this study demonstrates the potential of pindolol as a new treatment option for AUDs that can be fast-tracked into human clinical studies.

The α2-adrenergic receptor agonist, clonidine, reduces alcohol drinking in alcohol-preferring (P) rats

Evidence suggests that noradrenergic signaling may play a role in mediating alcohol-drinking behavior in both rodents and humans. We have investigated this possibility by administering clonidine to alcohol-drinking rats selectively bred for alcohol preference (P line). Clonidine is an α2-adrenergic receptor agonist which, at low doses, inhibits noradrenergic signaling by decreasing norepinephrine release from presynaptic noradrenergic neurons. Adult male P rats were given 24 h access to food and water and scheduled access to a 15% (v/v) alcohol solution for 2 h daily. Rats received intra-peritoneal (IP) injections with clonidine (0, 10, 20, 40, or 80 μg/kg body weight [BW], 10-11 rats/treatment group) once/day at 30 min prior to onset of the daily 2 h alcohol access period for 2 consecutive days. Clonidine, in doses of 40 or 80 μg/kg BW, significantly reduced alcohol intake on both days of treatment (p<0.001). Two weeks later, rats were treated with clonidine for 5 consecutive days and clonidine, in doses of 40 or 80 μg/kg BW, reduced alcohol intake on all 5 treatment days (p < 0.001). Clonidine did not alter water consumption during the daily 2 h free-choice between alcohol and water. In a separate group of male P rats, clonidine (40 μg/kg BW) suppressed intake of a saccharin solution (0.04 g/L). These results are consistent with and complement our previous findings that the α1-adrenergic receptor antagonist, prazosin, decreases voluntary alcohol drinking in alcohol-preferring rats, but suggests that effects of clonidine may not be specific for alcohol. The results suggest that although activation of the noradrenergic system plays an important role in mediating voluntary alcohol drinking, care is needed in selecting which drugs to use to suppress central noradrenergic signaling in order to maximize the selectivity of the drugs for treating alcohol-use disorders.

Elevated Norepinephrine may be a Unifying Etiological Factor in the Abuse of a Broad Range of Substances: Alcohol, Nicotine, Marijuana, Heroin, Cocaine, and Caffeine

A wide range of commonly abused drugs have effects on the noradrenergic neurotransmitter system, including alterations during acute intoxication and chronic use of these drugs. It is not established, however, that individual differences in noradrenergic signaling, which may be present prior to use of drugs, predispose certain persons to substance abuse. This paper puts forth the novel hypothesis that elevated noradrenergic signaling, which may be raised largely due to genetics but also due to environmental factors, is an etiological factor in the abuse of a wide range of substances, including alcohol, nicotine, marijuana, heroin, cocaine, and caffeine. Data are reviewed for each of these drugs comprising their interaction with norepinephrine during acute intoxication, long-term use, subsequent withdrawal, and stress-induced relapse. In general, the data suggest that these drugs acutely boost noradrenergic signaling, whereas long-term use also affects this neurotransmitter system, possibly suppressing it. During acute withdrawal after chronic drug use, noradrenergic signaling tends to be elevated, consistent with the observation that norepinephrine lowering drugs such as clonidine reduce withdrawal symptoms. Since psychological stress can promote relapse of drug seeking in susceptible individuals and stress produces elevated norepinephrine release, this suggests that these drugs may be suppressing noradrenergic signaling during chronic use or instead elevating it only in reward circuits of the brain. If elevated noradrenergic signaling is an etiological factor in the abuse of a broad range of substances, then chronic use of pharmacological agents that reduce noradrenergic signaling, such as clonidine, guanfacine, lofexidine, propranolol, or prazosin, may help prevent or treat drug abuse in general.

Prazosin reduces alcohol drinking throughout prolonged treatment and blocks the initiation of drinking in rats selectively bred for high alcohol intake

BACKGROUND

This study examined whether prazosin reduces alcohol drinking over the course of prolonged treatment and whether it blocks the initiation of alcohol drinking in rats with a genetic predisposition toward high alcohol drinking, that is alcohol-preferring (P) rats.

METHODS

In study one, alcohol-experienced P rats that had been drinking alcohol for 2 h/d for several months were treated daily with prazosin (0, 0.5, 1.0, or 2.0 mg/kg body weight [BW]) for 7 weeks. In study two, alcohol-naïve P rats were treated daily with prazosin (0, 1.0, or 2.0 mg/kg BW) for 2 weeks prior to, or concomitantly with, the initiation of alcohol access and throughout 3 weeks of alcohol availability. Prazosin treatment and alcohol access were then discontinued for 2 weeks followed by reinstatement of alcohol access without prazosin treatment for 4 weeks, followed by resumption of daily prazosin treatment (2.0 mg/kg BW) for 3 weeks.

RESULTS

Prazosin reduced alcohol drinking throughout 7 weeks of treatment in P rats accustomed to drinking alcohol. Following termination of prazosin treatment, alcohol drinking slowly returned to pretreatment baseline. Reduced alcohol intake was accompanied by increased water intake. In alcohol-naïve P rats, prazosin administration prior to the first opportunity to drink alcohol and throughout 3 weeks of alcohol access retarded acquisition of alcohol drinking and reduced the amount of alcohol consumed. When prazosin was administered concomitantly with the first opportunity to drink alcohol, it abolished acquisition of alcohol drinking. Discontinuation of prazosin treatment allowed expression of a genetic predisposition toward high alcohol drinking to gradually emerge. Prazosin retained the ability to reduce alcohol intake with repeated treatments.

CONCLUSIONS

Prazosin decreased alcohol drinking during prolonged treatment and may be useful for treating alcoholism and alcohol-use disorders. Prazosin may also be useful for deterring the initiation of drinking in individuals with a family history of alcoholism.

Differential patterns of alcohol consumption and dopamine-2 receptor binding in Wistar-Kyoto and Wistar rats

The Wistar-Kyoto (WKY) rat strain has been described as an animal model of depressive behavior that consumes significantly greater amounts of alcohol compared to the Wistar (WIS) rat strain. Since the mesolimbic dopamine (DA) type-2 (D2) receptors mediate reward-related behaviors, the present study measured the binding of [(125)I]-Iodosulpiride to D2 receptors in the brains of WKY versus WIS rats following 24 days of voluntary alcohol or water consumption. Alcohol consuming WKY rats showed a significant increase in D2 receptor binding in several regions of the mesolimbic and nigrostriatal systems. In contrast, alcohol consuming WIS rats showed a reduction in D2 receptor binding in DA cell body areas. The differential regulation of D2 receptors by voluntary alcohol consumption in the two rat strains suggests that D2 receptor mediated neurotransmission may be playing a role in the increased alcohol drinking behavior reported in WKY rats.

A longitudinal analysis of alcohol consumption and the risk of posttraumatic symptoms

BACKGROUND

Previous studies investigating the impact of alcohol ingestion on the emergence of posttraumatic psychological symptoms have generated contradictory findings.

METHODS

One thousand forty-five patients, admitted to hospital following traumatic injury were assessed during hospitalisation for patterns of alcohol consumption prior to the injury and also during the month prior to reassessment at 3 months. Anxiety, depression and posttraumatic stress disorder (PTSD) were assessed post accident and at 3 months. In a sub sample (n=167), blood alcohol levels were measured at the time of admission to emergency departments.

RESULTS

Moderate alcohol consumption prior to and following the accident predicted lower levels of psychological distress at 1 week and 3 months. No significant relationship was found between the blood alcohol level and psychiatric outcomes. PTSD predicted the emergence of alcohol abuse following the accident, suggesting self-medication in a subgroup of survivors.

LIMITATIONS

The impact of alcohol consumption upon injury severity and the nature of injury was not controlled for and some non-participation may have been related to patterns of alcohol consumption. We relied on retrospective reports of alcohol use obtained shortly after the traumatic injury to index prior alcohol use and these reports may have been influenced by mood states at the time of recall. Our follow-up was limited to 3 months and there is a need for longer-term assessment of the relationship between prior alcohol use and subsequent posttraumatic adjustment.

CONCLUSION

Given the potential impact of alcohol use on traumatic injury and post-injury recovery, we advocate active screening and early intervention strategies that focus on moderate alcohol usage.

The alpha1-adrenergic receptor antagonist, prazosin, reduces alcohol drinking in alcohol-preferring (P) rats

BACKGROUND

Preliminary evidence suggest that noradrenergic signaling may play a role in mediating alcohol drinking behavior in both humans and rats. Accordingly, we tested the hypothesis that blockade of alpha(1)-adrenergic receptors will suppress alcohol drinking in rats selectively bred for alcohol preference (P line).

METHODS

Adult male P rats were given 24-hour access to food and water and scheduled access to a 15% (v/v) alcohol solution for 2 hours daily. Rats were injected IP with the alpha(1)-adrenergic receptor antagonist, prazosin (0, 0.5, 1.0, 1.5, or 2.0 mg/kg body weight), once a day at 15 minutes prior to onset of the daily 2-hour 2-bottle choice, alcohol versus water, access period for 2 consecutive days and then 3 weeks later for 5 consecutive days.

RESULTS

Prazosin significantly reduced (p < 0.01) alcohol intake during the initial 2 daily administrations, and this reduction of alcohol intake was maintained for 5 consecutive days by daily prazosin treatment in the subsequent more prolonged trial (p < 0.05). The prazosin-induced reduction of alcohol intake was not dependent upon drug-induced motor impairment since increases in water drinking (p < 0.05) were exhibited during the 2-hour access periods during both 2- and 5-day prazosin treatment.

CONCLUSIONS

The results indicate that the noradrenergic system plays a role in mediating alcohol drinking in rats of the P line and suggest that prazosin--a safe, well-characterized, and well-tolerated drug--may be an effective pharmacotherapeutic agent for the treatment of alcohol use disorders.

Forebrain and hindbrain effects of ethanol on counterregulatory responses to hypoglycemia in conscious rats

Ethanol (OH) has been reported to blunt counterregulation and increase insulin sensitivity, thereby causing greater hypoglycemia in patients with diabetes mellitus. The aim of this study was to determine if fore- or hindbrain sensing of OH differentially affects autonomic and metabolic counterregulatory responses to hypoglycemia. Forty-one Sprague-Dawley rats received 5% OH or isotonic sodium chloride solution (or normal saline; SAL) infused peripherally or into the lateral (forebrain) or fourth cerebral ventricles (hindbrain) from time 0 to 120 minutes. From time 120 to 240 minutes, rats were exposed to a hyperinsulinemic (5 mU/[kg min]) hypoglycemic (2.9 +/- 0.1 mmol/L) clamp. The 4 groups of rats studied were as follows: SAL (n = 8), peripheral alcohol (POH) (n = 10), lateral ventricle alcohol (LVOH) (n = 12), and left ventricle alcohol (4VOH) (n = 11). After OH, basal levels of norepinephrine were lower in the POH and 4VOH groups (P < .05). Epinephrine and norepinephrine responses to hypoglycemia were significantly lower in POH, 4VOH, and LVOH vs SAL. However, the magnitude of blunting was significantly greater in POH and 4VOH vs LVOH. Other counterregulatory hormones and glucose kinetics were not significantly different among all groups during hypoglycemia. In summary, peripheral and central nervous system OH infusion blunted autonomic nervous system counterregulatory (epinephrine, norepinephrine) responses to subsequent hypoglycemia. The greater impact of 4VOH compared with LVOH administration suggests that OH exerts its effects to blunt autonomic nervous system counterregulatory responses during hypoglycemia primarily by actions on the hindbrain.

Chronic daily ethanol and withdrawal: 6. Effects on rat sympathoadrenal activity during "abstinence"

We have reported that repetitive daily ethanol consumption increased anxiety-like behavior in rats 4 weeks after ethanol consumption had ceased, consistent with the persistently increased anxiety exhibited by abstinent alcoholics. Increased anxiety is associated with sympathoadrenal activation, so we have now also investigated ethanol-induced persistent changes in basal and stress-induced plasma epinephrine (E) and norepinephrine (NE) levels. Male Sprague-Dawley rats received liquid diet containing ethanol versus pair-fed isocaloric control liquid diet for 9 weeks. After 5 weeks' subsequent "abstinence" (i.e., no ethanol in the diet), the control rats exhibited low basal plasma E and NE, which were both increased by 150-300% within 5 min after transfer to a novel cage in a novel room, returning toward basal levels within 15 min. "Abstinent" ethanol-treated rats exhibited elevated basal E levels (195% of controls, P<.05), which were not significantly altered by transfer to novel environment; basal NE levels tended (P<.07) to be elevated and likewise were not altered by novel environment. These results suggest that daily ethanol consumption can induce persistent increases in sympathoadrenal activation during subsequent "abstinence," which are relatively refractory to further stimulation.

Psychopharmacological possibilities in the acute disaster setting

This article focuses on possible psychopharmacological interventions in the immediate post disaster setting. As there is little evidence for the efficacy or effectiveness of such interventions-given the difficulty in performing randomized, double-blind, placebo controlled studies with these populations-the article will delineate the neurobiological basis for pathological sequelae and theoretical drug interventions targeting putative disease mechanisms.

Catecholamine depletion by reserpine blocks the anxiolytic actions of ethanol in the rat

Neurochemical investigations of the anti-anxiety action of ethanol demonstrate that increased dopaminergic, noradrenergic, and serotonergic activity mediates the anxiolytic actions of ethanol. Results of studies with animals and human beings also confirm an involvement of the sympathetic nervous system in the behavioral actions of ethanol. Because enhanced sympathetic activity increases the release of norepinephrine from sympathetic terminals, the interruption of normal sympathetic activity might disrupt the anxiolytic action of ethanol. The present study examined the effect of chemical sympathectomy by reserpine pretreatment on the subsequent anxiolytic action of ethanol. Seventy-one, female, Sprague-Dawley rats were administered reserpine (0 or 5 mg/kg), followed 17-19 h later by ethanol (0, 0.5, or 1.0 g/kg). Animals were then tested in the elevated plus maze. Compared with saline pretreatment, which did not attenuate the anxiolytic actions of a 1.0-g/kg dose of ethanol, reserpine pretreatment completely blocked the anxiolytic action of a 1.0-g/kg dose of ethanol. Reserpine, by itself, did not possess anxiolytic or anxiogenic actions. Because the anxiolytic action of ethanol involves increased catecholamine activity and the depletion of norepinephrine and dopamine from sympathetic nerve terminals by reserpine blocked the anxiolytic action of ethanol, it is concluded that the anxiolytic action of ethanol requires the presence of normal catecholamine activity. We suggest that prostaglandin activity normally evoked by enhanced sympathetic nervous system activity might be involved in the anxiolytic action of ethanol.

Behavioral and neurochemical changes following predatory stress in mice

This article had several objectives. First it aimed at investigating the anxiogenic-like behaviors elicited by unavoidable cat exposure and/or cat odor across nine strains of mice (BALB/c, C57BL/6, C3H, CBA, DBA/2, NMRI, NZB, SJL, Swiss) in a modified version of the free-exploration test. The second objective was to investigate possible neurochemical changes following cat exposure in Swiss mice by measuring the turnover of dopamine (DA), noradrenaline (NA) and serotonin (5-HT) in several brain regions known to be involved in the modulation of emotional processes (hippocampus, hypothalamus and striatum). Finally, the third objective was to examine the effects of anxiolytic drug treatments on the anxiogenic responses elicited by a cat odor (i.e. a feces) in Swiss mice previously exposed to a cat using the free-exploration test. Results from the strain comparison showed that mice could be divided into three distinct groups: two non-reactive strains (NZB and SJL) which were relatively insensitive to predatory exposure and/or odor; five intermediate-reactive strains (Swiss, NMRI, CBA, C3H and BALB/c) which displayed clear anxiogenic-like responses only when exposed to both cat and, subsequently, to feces; and two high reactive strains (C57BL/6 and DBA/2) which showed anxiogenic-like reactions following cat exposure, regardless of the stimulus (clay or feces) present in the free-exploration cage. Neurochemical data revealed that, while brain levels of NA, DA, 5-HT in cat exposed Swiss mice were not significantly different from those of control animals, turnover rates of these monoamines were increased in the hippocampus (NA and 5-HT), hypothalamus and striatum (DA) after cat exposure. Results from pharmacological experiments indicated that repeated administration of the 5-HT reuptake inhibitor fluoxetine (5-20 mg/kg, twice a day, for 5 days) completely abolished avoidance of the cat feces in Swiss mice previously exposed to the predator. Neither acute nor repeated administration of the classical anxiolytic diazepam was able to reduce avoidance behavior of the anxiogenic stimulus in the free-exploration test. Taken together, these findings indicate that the exposure of mice to unavoidable predatory stimuli is associated with behavioral and neurochemical changes consistent with increased anxiety.

Risk and preventive factors of post-traumatic stress disorder (PTSD): alcohol consumption and intoxication prior to a traumatic event diminishes the relative risk to develop PTSD in response to that trauma

BACKGROUND

Previous reports examined the effects of selected pre- (e.g. female gender, previous trauma), peri- (e.g. the horror of the trauma, threatened death) or post-exposure (e.g. the physical injury caused by the trauma) risk factors on the development of post-traumatic stress disorder (PTSD), an anxiety disorder associated with a traumatic event outside the range of usual human experience. We hypothesized that alcohol consumption prior to traumatic events may reduce the incidence rate of PTSD. The aim of this study was to examine the effects of the above risk factors and preventive factors, such as alcohol consumption, on the development of PTSD.

METHODS

An epidemiological cohort study was carried out on 127 victims trapped in a ballroom fire. Data were collected, 7-9 months after the traumatic event, by means of the Composite International Diagnostic Interview (CIDI) and structured interviews, aimed to assess the above pre-, peri- and post-exposure factors. Logistic regression analysis was used to examine the association of PTSD with the etiologic factors and to delineate those risk factors which contribute most to the development of PTSD.

RESULTS

Female gender, the number of previous trauma, a past history of simple phobia, threatened death, trauma exposure, hospitalization for trauma-induced injuries and the presence of burns increased the odds of PTSD, whereas a sense of control during the trauma, and alcohol consumption and intoxication decreased the odds of PTSD. Six factors made independent contributions to the prediction of PTSD, i.e. the number of previous trauma, a past history of simple phobia, loss of control (increase the odds), a sense of control, alcohol consumption and alcohol intoxication (decrease the odds).

CONCLUSIONS

The results of this study show that the development of PTSD is determined by the effects of pre-, peri- and post-exposure risk factors and may be prevented by the effects of peri-traumatic factors, such as sense of control, alcohol consumption and intoxication.

Ethanol induces taurine release in the amygdala: an in vivo microdialysis study

The effect of acute IP ethanol injections on the extracellular aspartate, glutamate, taurine and GABA content of the basolateral amygdala microdialysate was investigated in relationship with total brain ethanol. Each acute intraperitoneal injection of ethanol, 0.5, 1.0, 2.0 and 3.0 g/kg body weight, induced an immediate increase in microdialysate taurine; both 0.5 and 1.0 g/kg ethanol evoked an increase during the first 20 minutes following injection which returned to baseline value by 40 minutes, despite the fact that ethanol was detectable in the brain until 60 or 120 minutes, respectively. After either 2.0 or 3.0 g/kg ethanol there was an increase in taurine of gradual intensity which gradually declined to reach baseline values by 100 minutes. In contrast, the ethanol concentration for 2.0 g/kg remained elevated at the end of the 120 minutes; approximately 25 mg ethanol/mg protein. The stimulated release of taurine within the amygdala could participate in the regulation of ethanoli-nduced changes in osmolarity, since taurine is postulated to act as an osmoregulator in the brain. Taurine could also mediate or interact with ethanol-induced central nervous system effects, as it exerts a modulatory action on cell excitability and neurotransmitter processes.

The Neurobiological Basis of Anxiety and Fear: Circuits, Mechanisms, and Neurochemical Interactions (Part II)

This article is Part II of a review of the neuronal circuits, neural mechanisms, and neuromodulators that seem to be involved in anxiety and fear states. Part I focused on the specific brain structures, including the roles of the amygdala, locus coeruleus, hippocampus, and various cortical regions and the neural mechanisms of fear conditioning, extinction, and behavioral sensitization in mediating the signs and symptoms of anxiety and fear. Part II attempts to develop a better understanding of neurochemical mediation of traumatic remembrance and the neurobiological consequences of stress, particularly when experienced early in life. Finally, the data is synthesized to provide a basis for understanding the pathophysiology of anxiety disorders, such as Panic disorder and Posttraumatic Stress Disorder. NEUROSCIENTIST 4:122–132, 1998

The role of ethanol availability on stress-induced increases in ethanol consumption

Exposure to stressors can increase ethanol consumption and ethanol can attenuate the behavioral and biochemical effects of stressors. This study determined whether the availability of ethanol during the period of exposure to repeated restraint alters the poststress increase in ethanol intake. Seven days of restraint increased ethanol intake on the first poststress test only in animals deprived of ethanol during the restraint period. These results indicate that the availability of ethanol during exposure to restraint can attenuate the impact of restraint on ethanol intake. Ethanol intake was also positively related to novelty-induced locomotion and restraint eliminated this relationship. However, amphetamine-induced locomotion was not altered by either restraint or EtOH intake. These results indicate that voluntary ethanol intake can attenuate the impact of restraint stress and that restraint stress can alter the influence of ethanol on novelty-induced locomotion. It is suggested that this symmetrical relationship between ethanol intake and restraint stress may be involved in an interactive manner that determines stress-induced ethanol consumption.

Noradrenergic mechanisms in stress and anxiety: I. Preclinical studies

There is considerable preclinical evidence for a relationship between noradrenergic brain systems and behaviors associated with stress and anxiety. The majority of noradrenergic neurons are located in the locus coeruleus (pons), with projections throughout the cerebral cortex and multiple subcortical areas, including hippocampus, amygdala, thalamus, and hypothalamus. This neuroanatomical formation of the noradrenergic system makes it well suited to rapidly and globally modulate brain function in response to changes in the environment, as occurs during the presentation of stressors. Stress exposure is associated with an increase in firing of the locus coeruleus and with associated increased release and turnover of norepinephrine in brain regions which receive noradrenergic innervation. Increased firing of the locus coeruleus is also associated with behavioral manifestations of fear, such as arched back and piloerection in the cat. Exposure to chronic stress results in long-term alterations in locus coeruleus firing and norepinephrine release in target brain regions of the locus coeruleus. Norepinephrine is also involved in neural mechanisms such as sensitization and fear conditioning, which are associated with stress. These findings are relevant to an understanding of psychiatric disorders, such as panic disorder and post-traumatic stress disorder (PTSD), the symptoms of which have been hypothesized to be related to alterations in noradrenergic function.

Extraversion as a modifying factor in catecholamine and behavioral responses to ethanol

Individual differences in catecholamine response to stress and ethanol were tested in extraverts and introverts on the basis of Eysenck's drug postulate claiming that introverts would be less susceptible to sedative drugs like ethanol. Forty-four healthy males received either 0.8 g/kg ethanol mixed into a drink of caffeine-free cola or a respective placebo and were tested with a stressful mental arithmetic task before and 40 min after the intake of the drink. Plasma catecholamines were determined from blood samples drawn at five defined intervals from an indwelling cannula and self-ratings on deactivation, relaxation, and anxiety were obtained as well as quality and quantity of performance in the arithmetic task. Results showed that there was no difference in catecholamine stress responses between introverts (Ex -) and extraverts (Ex +) before the drink, but that the intake of the fluid (both ethanol and placebo) resulted in higher norepinephrine (NE) increases in Ex - than in Ex +. The combined effects of ethanol and stress yielded larger responses of longer durations in Ex - than in Ex +. The concomitant psychological changes showed larger reductions in anxiety and increases in relaxation as well as larger decrements in quality of performance (% errors) in introverts in spite of their higher catecholamine increases. Thus, the predictions on the basis of arousal theory could not be verified experimentally and the drug postulate has to be modified in the sense that introverts probably have a higher depletion of NE in the central nervous system under physical but not under mental stress which is reflected by higher levels in the plasma and respective decreases in performance and activation.

Restraint stress in biomedical research: an update

Since the publication of our initial review of restraint stress in 1986, much work has continued with this technique, either as a tool for the investigation of other pharmacological, physiological, or pathologic phenomena or with restraint stress itself serving as the object of the study. As we noted in 1986, the major use of restraint has been for the induction of stress responses in animals and, more specifically, for the investigation of drug effects, particularly as they affect typical stress-related pathology--gastrointestinal, neuroendocrine, and immunological agents have been extensively studied. In compiling this update on restraint stress and its effects, we noted an increasing emphasis on central nervous system mechanisms in peripheral disease, especially gastrointestinal disease. In particular, many CNS-active agents have been tested for their effects on gastric and duodenal lesion formation and gastric secretion, including antidepressants, antipsychotics, anxiolytics, noradrenergic, serotonergic, dopaminergic, and peptidergic compounds. Some of these agents are especially active in the gastrointestinal tract even when administered centrally, further solidifying the concept of a brain-gut axis. The present update includes studies of: methods and procedures, pre-restraint manipulations, post-restraint/healing effects, and drug effects. In addition, a current bibliography of reports that have employed restraint is included.

Ethanol alters monoamines in specific mouse brain regions

Ethanol (3.5 g/kg 60 min post-IP injection) produced the following changes in regional brain monoamine levels and in the respective metabolite/neurotransmitter ratios: for the noradrenergic system, MHPG was decreased in the amygdala and increased in the hypothalamus, while the MHPG/NE ratio was increased in the prefrontal cortex and the hypothalamus. For the dopaminergic system, DA was decreased in the olfactory tubercle, DOPAC was increased in the prefrontal cortex and septum, and DOPAC/DA was increased in the prefrontal cortex, septum, striatum, and hypothalamus. HVA was increased in the prefrontal cortex and septum, while HVA/DA was increased in the same regions plus the olfactory bulb. 3MT was decreased in the olfactory tubercle and striatum. The serotonergic system was not altered. The results demonstrate that ETOH produces selective regional changes in the concentration and utilization of monoamines in mouse brain with a predominant influence on dopaminergic systems and a lesser effect on noradrenergic activity.

Effects of age and alcoholism on the prevalence of panic disorder

Findings are reported evaluating the effects of aging and alcoholism histories on the 6-month prevalence rates of panic disorder. The data were collected in 5 communities as part of the Epidemiologic Catchment Area (ECA) study: New Haven, CT; Baltimore, MD; St. Louis, MO; Durham, NC; and Los Angeles, CA. Reanalysis of ECA data provided additional support for a decline in the prevalence of panic disorder among elderly people. In addition, the presence of a history of alcohol abuse or dependence was associated with significantly elevated panic disorder rates in younger individuals, but an earlier decline in panic disorder prevalence with age, regardless of gender. These findings offer preliminary support for neurodevelopmental hypotheses for the onset and outgrowing of panic disorder. They also highlight the impact of alcoholism on the course of panic disorder.

Direct evidence of conditioned fear-elicited enhancement of noradrenaline release in the rat hypothalamus assessed by intracranial microdialysis

Inescapable footshock stress produced marked increases in noradrenaline (NA) release, which was assessed by intracranial microdialysis, in the hypothalamus of conscious rats. Emotional stress, without physical stimuli (replacement to the environment where the rats had received footshock previously), also increased hypothalamic NA release. These results suggest that foodshock stress caused increases in NA release and this activation of NA neurons appears to be reinstated simply by re-exposure to the environment previously associated with shock.

Pentobarbital attenuates stress-induced increases in noradrenaline release in specific brain regions of rats

To examine whether anxiolytic action of drugs acting at the GABA/BZD-chloride channel complex may be related to the brain noradrenergic system, we investigated the effect of pentobarbital, a typical barbiturate which has potent GABA modulating properties, on increased NA release in nine brain regions of stressed rats. Pentobarbital (10 and 25 mg/kg) was injected IP 65 min before sacrifice (5 min before one-hour immobilization stress). Levels of 3-methoxy-4-hydroxyphenylethyleneglycol sulfate (MHPG-SO4), the major metabolite of brain noradrenaline (NA), and of plasma corticosterone, were fluorometrically determined. Pentobarbital treatment by itself increased MHPG-SO4 levels in the thalamus, locus coeruleus (LC) region, midbrain and basal ganglia of nonstressed rats. Stress produced increases in MHPG-SO4 levels in all brain regions examined and elevation of plasma corticosterone levels. Pentobarbital attenuated, in a dose-dependent manner, stress-induced increases in MHPG-SO4 levels in the hypothalamus, thalamus, anterior cerebral cortex, LC region and basal ganglia and also attenuated the stress-induced elevation of plasma corticosterone levels. These data suggest that pentobarbital can attenuate both stress-induced increases in NA release in specific brain regions as well as activation of the hypothalamo-pituitary-adrenocortical system. These attenuating effects may be related to the anxiolytic action of barbiturates.

Met-enkephalin, injected during the early phase of stress, attenuates stress-induced increases in noradrenaline release in rat brain regions

By measuring levels of 3-methoxy-4-hydroxyphenylethyleneglycol sulfate (MHPG-SO4), the major metabolite of noradrenaline (NA), we investigated the effects of Met-enkephalin (Met-ENK) ICV injected at three different stages of stress, i.e., 0 min, 5 min, or 10 min after exposure to immobilization stress. Immobilization stress caused significant increases in MHPG-SO4 levels in all brain regions examined, i.e., the hypothalamus, amygdala, thalamus, midbrain, hippocampus and locus coeruleus (LC), which suggests that stress increases NA release in these regions. Met-ENK at a dose of 50 micrograms, injected ICV immediately before stress exposure significantly attenuated stress-induced increases in MHPG-SO4 in the amygdala, thalamus and LC, but did not have such an effect when injected either 5 min or 10 min or 10 min after exposure to stress. Similarly, Met-ENK at 150 micrograms at 0 min significantly attenuated these increases in all brain regions examined, however, it did not do so when given at 5 min or 10 min after stress initiation. The amount of defecation and the weight loss caused by stress were also significantly attenuated by Met-ENK injected but only at 0 min. These results suggest that the attenuating effect of Met-ENK on stress-induced increases in NA release is greatly affected by the time of the peptide administration and that Met-ENK might inhibit stress-induced increases in NA release in these regions by affecting the initial changes induced by stress.

Involvement of noradrenergic system in a remarkably rapid tongue clonus produced by acute hypnotic doses of ethanol in Fischer F344 rats

Ethanol (2.95 g/kg, IP) eliminated the righting reflex and induced vigorous tongue clonus spontaneously or following tactile tongue stimulation in Fischer F344 rats. Responses normally lasted 30-60 min, and was reinstated by tactile stimulation in those cases where it subsided quickly. Sub-hypnotic (1.95 g/kg) or high (3.95 g/kg) doses failed to elicit clonus, even after tactile stimulation. A lipophilic alpha 1-adrenergic agonist (St 587) promptly initiated tongue clonus in rats treated with a 3.95 g/kg dose of ethanol. Prazosin, a selective alpha 1-adrenergic antagonist, blocked clonus, while the dopamine selective antagonist pimozide failed to modify this response. We infer an alpha 1-adrenergic effect in which norepinephrine is released by ethanol.