Introversion and extroversion: implications for depression and suicidality

A growing body of information suggests that core or underlying personality is a significant concomitant of depression and suicidality. Introversion (ie, low extroversion) is especially promising in its relationship to the phenomenology and outcome of depression, and may represent an underlying heritable trait of etiologic significance. Furthermore, the presence of introversion has implications for differentiating unipolar and bipolar depression. It is likely that introversion acts in concert with other core personality variables, including neuroticism and having a feeling-type personality to influence depression. Considering depression from the perspective of core personality allows for novel psychotherapeutic approaches based on targeting underlying personality variables.

Core heritable personality characteristics and relapse in alcoholics

This article represents the proceedings of a symposium at the 2000 ISBRA Meeting in Yokohama, Japan. The chairs were David S. Janowsky and Jan Fawcett. The presentations were (1) The tridimensional personality questionnaire: Predictor of relapse in detoxified alcoholics, by Kurt Meszaros; (2) Novelty seeking predicts clinical trial attrition in alcoholics, by Jan Fawcett; (3) Personality and alcohol/substance use disorder patient relapse and attendance at self-help group meetings, by David S. Janowsky; and (4) A three-pathway psychobiological model for craving for alcohol, by Roel Verheul.

Over-representation of Myers Briggs Type Indicator introversion in social phobia patients

The purpose of this study is to profile the personalities of patients with social phobia. Sixteen patients with social phobia were compared with a normative population of 55,971, and with 24 hospitalized Major Depressive Disorder inpatients, using the Myers Briggs Type Indicator. The Myers Briggs Type Indicator, a popular personality survey, divides individuals into eight categories: Extroverts versus Introverts, Sensors versus Intuitives, Thinkers versus Feelers, and Judgers versus Perceivers. Social phobia patients were significantly more often Introverts (93.7%) than were subjects in the normative population (46.2%). In addition, using continuous scores, the social phobia patients scored as significantly more introverted than did the patients with Major Depressive Disorder, who also scored as Introverted. Introversion is a major component of social phobia, and this observation may have both etiological and therapeutic significance.

Combination pharmacotherapy: a mixture of small doses of naltrexone, fluoxetine, and a thyrotropin-releasing hormone analogue reduces alcohol intake in three strains of alcohol-preferring rats

It is common to treat some diseases with more than one medication simultaneously. Since more than one neurotransmitter system is involved in alcohol-seeking behaviour, then a therapeutic approach that targets more than one system should be more effective in reducing alcohol intake than one addressing a single system. To test this hypothesis, we compared the efficacy of low doses of individual drugs reported to reduce voluntary alcohol drinking to the efficacy of a mixture of these agents at the same low doses in reducing alcohol intake in three strains of alcohol-preferring rats (P, HAD, and Fawn-Hooded). After establishment of a stable baseline for alcohol intake in a continuous access paradigm, each rat received separate single i.p. injections of relatively low doses of either naltrexone (2.0 mg/kg), fluoxetine (1.0 mg/kg), the thyrotropin-releasing hormone analogue TA-0910 (0.2 mg/kg), a mixture of all three drugs, or the vehicle at 09:30. Each rat received all treatments, with an inter-injection washout period of at least 3 days. Alcohol and water intakes were measured at 6 and 24 h, and food intake was measured at 24 h, after the injection. Our results show that individual drugs did not significantly affect food, water, or alcohol intake. However, the mixture significantly reduced alcohol intake in all three strains, but had no effect on food intake. Similar results were obtained when the HAD rats received an oral dose of the individual drugs or the mixture. When P rats were given an i.p. injection of the mixture for 10 consecutive days, there was a continued suppressing effect. These findings show that a combination treatment designed to target simultaneously serotonergic, dopaminergic, and opioidergic systems can reduce alcohol intake, even though the doses of the individual drugs in the mixture are relatively low and ineffective when given singly.

New treatments of bipolar disorder

This clinical trials review is derived from the presentations made at the Third International Conference on Bipolar Disorder, held June 17-19, 1999 in Pittsburgh, PA, published as abstracts in Bipolar Disorders: An International Journal of Psychiatry and Neurosciences, Edited by Jair C. Soares, and Samuel Gershon. In this review, abstracts reporting on the efficacy of "third generation" anti-epileptic agents, including topiramate, lamotrigine, diphenylhydantoin, gabapentin, and the new generation antipsychotic agent, olanzapine in treating bipolar disorders are reviewed.

Myers Briggs Type Indicator and Tridimensional Personality Questionnaire differences between bipolar patients and unipolar depressed patients

OBJECTIVES

The current study was designed to compare personality differences between bipolar patients and unipolar depressed patients, as evaluated on the Myers Briggs Type Indicator (MBTI) and the Tridimensional Personality Questionnaire (TPQ).

METHODS

A group of bipolar and a group of unipolar depressed patients filled out the MBTI, the TPQ, the Beck Depression Inventory, and the CAGE questionnaire. The two groups were compared with each other as to responses on the above surveys, and subgroups of bipolar depressed and bipolar patients with manic symptoms were also compared.

RESULTS

Bipolar patients were found to be significantly more extroverted (p = 0.004) and less judging (p = 0.007) on the MBTI. They were significantly more novelty seeking (p = 0.004) and less harm avoidant (p = 0.002) on the TPQ. Of the above differences, only the TPQ harm avoidance scale appeared strongly linked to the patients' level of depression.

CONCLUSION

Significant differences in personality exist between bipolar disorder and unipolar depressed patients.

Personality and alcohol/substance-use disorder patient relapse and attendance at self-help group meetings

This study evaluated the role of personality in the short-term outcome of alcohol/substance-use disorder patients. Detoxifying alcohol/substance-use disorder patients were administered the Myers-Briggs Type Indicator (MBTI), the Tridimensional Personality Questionnaire (TPQ), the Michigan Alcohol Screening Test (MAST), the CAGE Questionnaire, and the Beck Depression Inventory (BDI). These patients were subsequently evaluated over a 1-month period for relapse and attendance at self-help group meetings. High TPQ Persistence scale scores predicted abstinence. When the Thinking and Feeling groups were considered separately, and when these two groups were combined into a single group, high scores for the individual groups and the combined group (i.e. Thinking and Feeling types together) predicted abstinence. High TPQ Persistence scale scores and low Shyness with Strangers and Fear of Uncertainty subscale scores predicted attendance at self-help group meetings. High MBTI Extroversion and high MBTI Thinking scores also predicted attendance at self-help group meetings. When the Extroverted and Introverted types and the Thinking and Feeling types respectively were combined, as with abstinence, high scores predicted attendance at self-help group meetings. Age, gender, CAGE, MAST, and BDI scores did not predict outcome. The above information suggests that specific personality variables may predict abstinence and attendance at self-help group meetings in recently detoxified alcoholics, and this may have prognostic and therapeutic significance.

Underlying personality differences between alcohol/substance-use disorder patients with and without an affective disorder

The Myers-Briggs Type Indicator (MBTI), a popular personality test, was used to profile the personalities of in-patient alcoholics/substance-use disorder patients who had, and those who did not have, a concurrent affective disorder diagnosis. The MBTI divides individuals into eight categories: Extroverts and Introverts, Sensors and Intuitives, Thinkers and Feelers, and Judgers and Perceivers. Alcohol/substance-use disorder patients with no affective disorder differed from a normative population only in being significantly more often Sensing and significantly less often Intuitive single-factor types. The Extroverted/Sensing/ Feeling/Judging four-factor type was also significantly over-represented in this group, compared to a normative population. In contrast, mood-disordered alcohol/substance-use disorder patients were significantly more often Introverted, Sensing, Feeling, and Perceiving and significantly less often Extroverted, Intuitive, Thinking, and Judging single-factor types. They were also significantly more often Introverted/Sensing/ Feeling/Perceiving and Introverted/Intuitive/Feeling/Perceiving four-factor types. 'Pure' alcohol/ substance-use disorder patients differed from alcohol/substance-use disorder patients with a mood disorder in that they were significantly more often Extroverted and Thinking and significantly less often Introverted and Feeling single-factor types; and significantly less often were an Introverted/Sensing/ Feeling/Perceiving four-factor type. The above results may have psychogenetic, diagnostic, and psychotherapeutic implications.

Association between preference for sweets and excessive alcohol intake: a review of animal and human studies

This report reviews a series of studies demonstrating a relationship between the consumption of sweets and alcohol consumption. There is consistent evidence linking the consumption of sweets to alcohol intake in both animals and humans, and there are indications that this relationship may be at least partially genetic in nature. Alcohol-preferring rats have a tendency to consume sucrose and saccharin solutions far beyond the limits of their normal fluid intake and this has been proposed to be a model of the clinical phenomenon known as loss of control. Furthermore, rats and mice, genetically bred to prefer alcohol, tend to choose more concentrated sweet solutions, compared to animals which do not prefer alcohol. Similar tendencies to prefer ultra-sweet solutions have been noted in studies of alcoholic subjects, with most alcoholics preferring sweeter sucrose solutions than do controls. Evidence also exists that those alcoholics who prefer sweeter solutions may represent a familial form of alcoholism. Finally, consumption of sweets and/or sweet solutions may significantly suppress alcohol intake in both animals and in alcoholics. Carbohydrate structure and sweet taste may contribute to this effect through different physiological mechanisms involving serotonergic, opioid, and dopaminergic functions. The possibility that there is concordance between sweet liking and alcohol consumption and/or alcoholism has theoretical, biological, and diagnostic/practical implications.

Antidepressant effects of nicotine in an animal model of depression

Epidemiological studies indicate a high incidence of cigarette smoking among depressed individuals. Moreover, individuals with a history of depression have a much harder time giving up smoking. It has been postulated that smoking may reflect an attempt at self-medication with nicotine by these individuals. Although some animal and human studies suggest that nicotine may act as an antidepressant, further verification of this hypothesis and involvement of nicotinic cholinergic system in depressive symptoms is required. Flinders Sensitive Line (FSL) rats have been proposed as an animal model of depression. These rats, selectively bred for their hyperresponsiveness to cholinergic stimulation, show an exaggerated immobility in the forced swim test compared to their control Flinders Resistant Line (FRL) rats. Acute or chronic (14 days) administration of nicotine (0.4 mg/kg s.c.) significantly improved the performance of the FSL but not the FRL rats in the swim test. The effects of nicotine on swim test were dissociable from its effects on locomotor activity. Moreover, the FSL rats had significantly higher [3H]cytisine binding (selective for the alpha4beta2 nicotinic receptor subtype) but not [125I]alpha-bungarotoxin binding (selective for the alpha7 subtype) in the frontal cortex, striatum, midbrain and colliculi compared to FRL rats. These data strongly implicate the involvement of central nicotinic receptors in the depressive characteristics of the FSL rats, and suggest that nicotinic agonists may have therapeutic benefits in depressive disorders.

Preference for higher sugar concentrations and Tridimensional Personality Questionnaire scores in alcoholic and nonalcoholic men

Animal studies have shown a positive association between the consumption of high concentrations of sweet solutions and subsequent alcohol intake. In a previous clinical study, it was shown that a preference for a high (0.83 M) concentration of sucrose (sweet liking) is characteristic of alcoholics, compared with controls. The present study was designed to determine whether personality variables, reported to be associated with subtypes of alcoholism, differentiate sweet liking alcoholics from sweet liking controls. Fifty-two male controls and 26 alcoholic patients were tested for sweet preference and administered the Tridimensional Personality Questionnaire. Sweet liking alcoholics scored significantly higher on the Tridimensional Personality Questionnaire Novelty Seeking and Harm Avoidance scales and related subscales when compared with sweet liking controls. Further analysis showed that preferred sucrose concentration, Harm Avoidance score, and Novelty Seeking predicted alcoholic versus nonalcoholic group status at 65% sensitivity and 94% specificity, with a correct classification in 85% subjects. We hypothesize that sweet liking may identify a specific alcoholism subtype also characterized by high novelty seeking and high harm avoidance. These findings may have theoretical biological significance and practical clinical implications.

Cholinergic/serotonergic interactions in hypothermia: implications for rat models of depression

This article reviews published reports and presents new evidence that support a number of commonalties between lines of rats selectively bred for differences in cholinergic (muscarinic) and serotonergic (5-HT1A) sensitivity. The Flinders Sensitive Line (FSL) rat, a genetic animal model of depression derived for cholinergic supersensitivity, is more sensitive to both cholinergic and serotonergic agonists, and exhibits exaggerated immobility in the forced swim test relative to the control, Flinders Resistant Line (FRL), rat. Similar exaggerated responses are seen in a line of rats recently selected for increased sensitivity to the 5-HT1A agonist, 8-OH-DPAT (High DPAT Sensitive--HDS), relative to lines selectively bred for either low (Low DPAT Sensitive--LDS) or random (Random DPAT Sensitive--RDS) sensitivity to 8-OH-DPAT. For both the FSL and HDS rats, their exaggerated immobility in the forced swim test is reduced following chronic treatment with antidepressants. The present studies examined further the interaction between cholinergic and serotonergic systems in the above lines. Supersensitive hypothermic responses to 8-OH-DPAT were observed very early (postnatal day 18) in FSL rats, suggesting that both muscarinic and serotonergic supersensitivity are inherent characteristics of these rats. Scopolamine, a muscarinic antagonist, completely blocked the hypothermic effects of the muscarinic agonist oxotremorine in FSL and FRL rats, but had no effect on the hypothermic responses to 8-OH-DPAT, suggesting an independence of muscarinic and 5-HT1A systems. On the other hand, genetic selection of genetically heterogeneous rats for differential hypothermic responses to the muscarinic agonist oxotremorine were accompanied by differential hypothermic responses to 8-OH-DPAT, suggesting an interaction between muscarinic and 5-HT1A systems. Overall, these studies argue for an inherent interaction between muscarinic and 5-HT1A systems, which probably occurs beyond the postsynaptic receptors, possibly at the level of G proteins.

Potential animal model of multiple chemical sensitivity with cholinergic supersensitivity

Multiple Chemical Sensitivity (MCS) is a clinical phenomenon in which individuals, after acute or intermittent exposure to one or more chemicals, commonly organophosphate pesticides (OPs), become overly sensitive to a wide variety of chemically-unrelated compounds, which can include ethanol, caffeine and other psychotropic drugs. The Flinders Sensitive Line (FSL) rats were selectively bred to be more sensitive to the OP diisopropylfluorophosphate (DFP) compared to their control counterparts, the Flinders Resistant Line (FRL) rats. The present paper will summarize evidence which indicates that the FSL rats exhibit certain similarities to individuals with MCS. In addition to their greater sensitivity to DFP, the FSL rats are more sensitive to nicotine and the muscarinic agonists arecoline and oxotremorine, suggesting that the number of cholinergic receptors may be increased, a conclusion now supported by biochemical evidence. The FSL rats have also been found to exhibit enhanced responses to a variety of other drugs, including the serotonin agonists m-chlorophenylpiperazine and 8-OH-DPAT, the dopamine antagonist raclopride, the benzodiazepine diazepam, and ethanol. MCS patients report enhanced responses to many of these drugs, indicating some parallels between FSL rats and MCS patients. The FSL rats also exhibit reduced activity and appetite and increased REM sleep relative to their FRL controls. Because these behavioral features and the enhanced cholinergic responses are also observed in human depressives, the FSL rats have been proposed as a genetic animal model of depression. It has also been reported that MCS patients have a greater incidence of depression, both before and after onset of their chemical sensitivities, so cholinergic supersensitivity may be a state predisposing individuals to depressive disorders and/or MCS. Further exploration of the commonalities and differences between MCS patients, human depressives, and FSL rats will help to elucidate the mechanisms underlying MCS and could lead to diagnostic approaches and treatments beneficial to MCS patients.

Suppression of alcohol intake after administration of the Chinese herbal medicine, NPI-028, and its derivatives

The Chinese herbal medicine, NPI-028, has been used for centuries in China to counteract alcohol intoxication. The present study used a number of different experimental conditions to determine whether NPI-028 and its derivatives might selectively influence alcohol intake in rodents that naturally exhibit high alcohol intakes. It was determined that intraperitoneal (i.p.) injections of NPI-028 (0.5, 0.75, and 1.0 g/kg) suppressed alcohol intake by up to 30% in both alcohol-preferring P and Fawn-Hooded (FH) rats during a continuous access schedule. These injections did not significantly affect food or water intakes, nor did the highest dose of NPI-028 (1 g/kg) alter blood ethanol levels after an i.p. injection of 2.5 g/kg of ethanol. In P rats, it was found that NPI-028 was orally active with the dose of 1.5 g/kg having a greater effect on ethanol intake than the 1.0 g/kg dose; once again, food and water intakes were not significantly altered. In FH rats maintained on a limited access schedule (1 hr/day), alcohol intake was completely abolished by 1.5 g/kg of NPI-028. Chronic i.p. administration of NPI-028 (0.75 g/kg) for four consecutive days in FH rats maintained on a continuous access schedule did not lead to any diminution of its alcohol-suppressant effects. Thus, NPI-028 has significant effects on alcohol intake without much effect on water and food intake, and tolerance does not readily develop to these effects. The i.p. administration of a partially purified extract (NPI-031) of NPI-028, obtained by countercurrent chromatography, also dose-dependently suppressed ethanol intake in FH rats, but the highest dose 200 mg/kg) also significantly decreased food intake. Finally, the i.p. administration of puerarin (NPI-31G), an isoflavone isolated from NPI-031 by countercurrent chromatography, significantly reduced ethanol intake in FH rats without affecting food or water intake. Therefore, NPI-028 and one of its pure components, NPI-031G, selectively reduced ethanol intake in alcohol-preferring rats.

Further selection of rat lines differing in 5-HT-1A receptor sensitivity: behavioral and functional correlates

It was previously reported that selection for differences in the hypothermic effects to the selective 5-HT-1A agonist, 8-OH-DPAT, occurred rapidly, with very substantial differences present by the fourth generation. The present communication summarizes the findings from the next five generations of selection and from behavioral and other functional studies on these rats. The rats which were more sensitive to 8-OH-DPAT (High DPAT Sensitive-HDS) exhibited decreases in temperature of 4 degrees C or more and the distribution did not overlap with that of the rats which were less sensitive to 8-OH-DPAT (Low DPAT Sensitive-LDS) which exhibited decreases in temperature of 1.5 degrees C or less. The randomly bred control group (Random DPAT Sensitive-RDS) exhibited intermediate temperature decreases (means of 1.6-1.8 degrees C), with time overlap with the distributions of the selected groups. Pretreatment with pindolol, a 5-HT-1A antagonist, reduced the hypothermic response to 8-OH-DPAT, but pretreatment with ritanserin, a 5-HT-7 and 5-HT-2A/C antagonist, had no effect, confirming that the hypothermic response to 8-OH-DPAT is mediated predominantly by 5-HT-1A receptors. The HDS rats were less mobile in a forced swim test and drank more saccharin solution in a two-bottle choice paradigm than the LDS or RDS rats over several generations. In contrast, there were no consistent differences among the groups for open field activity or performance in an elevated plus maze. There were no differences among the groups for voluntary alcohol intake, but the HDS rats exhibited greater suppression of alcohol and saccharin intake after injection of 8-OH-DPAT (0.125 mg kg-1). The HDS rats were also found to have a higher number of 5-HT-1A binding sites in cortical regions than the LDS or RDS rats, but there were no 5-HT-1A binding site differences in the raphe nuclei. These findings clearly show that consistent behavioral differences do occur in the 8-OH-DPAT-selected lines of rats, but only for behaviors related to possible depression or reward, not anxiety. The pattern of binding results suggests that these behavioral correlates of 8-OH-DPAT selection may be related to changes in cortical 5-HT-1A receptors rather than raphe autoreceptors.

Administration of antidepressants, diazepam and psychomotor stimulants further confirms the utility of Flinders Sensitive Line rats as an animal model of depression

Flinders Sensitive Line (FSL) rats have been proposed as an animal model of depression because they resemble depressed humans in that they have elevated REM sleep, reduced activity, and increased immobility and anhedonia after exposure to stressors. The present paper reviews experiments on the drug treatment of FSL and control Flinders Resistant Line (FRL) rats related to their utility as an animal model of depression, and presents new information. FSL rats exhibited exaggerated immobility in the forced swim test which is counteracted by the tricyclic antidepressants imipramine and desipramine and the serotonin reuptake blocker sertraline; the low immobility exhibited by the FRL rats is generally unaffected by these compounds. In contrast to these "therapeutic" effects of well recognized antidepressants, lithium and bright light treatment did not alter the exaggerated immobility of FSL rats. Novel data indicated that neither FSL nor FRL rats exhibited alterations in swim test immobility following chronic administration of the psychomotor stimulant amphetamine (2 mg/kg) and the anticholinergic scopolamine (2 mg/kg), which typically reduce immobility after acute administration. However, it was found that the calcium channel blockers verapamil (5 and 15 mg/kg) and nicardipine (10 mg/kg) did reduce the exaggerated immobility in FSL rats following chronic administration, suggesting that these compounds need to be evaluated further in humans. Previous studies have indicated no differences between FSL and FRL rats evaluated in the elevated plus maze, either at baseline or after the administration of diazepam, suggesting that the FSL rat may not differ from controls in anxiety-related behavior. Another recently published study showed that the FSL rat also did not differ from normal Sprague-Dawley rats in startle tests, indicating that the FSL rats do not exhibit behaviors shown in animal models of schizophrenia. These findings confirm the utility of FSL rats as an animal model of depression because the FSL rats do not appear to exhibit behaviors analogous to anxiety or schizophrenia and because they respond "therapeutically" to antidepressants and not psychomotor stimulants.

Suppression of ethanol intake in alcohol-preferring rats by prior voluntary saccharin consumption

In a situation offering a free choice between 0.1% saccharin solution and tap water, Fawn Hooded (FH) rats consumed 363.0 +/- 33.5 ml/kg/day of saccharin solution. Subsequently those animals drank 3.0 +/- 0.4 g/kg of ethanol in a free choice between water and 10% ethanol solution. Control FH rats that did not have access to saccharin consumed 5.0 +/- 0.5 between groups was significant: p = 0.006). When control rats were exposed to the choice between 10% ethanol solution and 0.1% saccharin solution for 4 days they consumed 383.7 +/- 27.5 ml/kg/day of saccharin solution and their ethanol intake dropped to 1.2 +/- 0.3 g/kg/day. When these rats were returned back to alcohol/water choice and exposure to saccharin was discontinued, their alcohol intake was still reduced (3.7 +/- 0.3 g/kg/day for at least 10 consecutive days). Exposure of alcohol-experienced alcohol-preferring P rats with high (6.8 +/- 0.5 g/kg/day) and stable alcohol intake to saccharin/water choice for 4 days also resulted in a significant attenuation of their ethanol intake for at least 6 days following saccharin cessation. Thus, voluntary consumption of saccharin can suppress subsequent alcohol intake in both alcohol-naive and alcohol-experienced rats.

Saccharin-induced increase in daily fluid intake as a predictor of voluntary alcohol intake in alcohol-preferring rats

This study examined the relationship between saccharin intake and ethanol consumption in alcohol preferring (P) rats and Fawn Hooded (FH) rats before and after exposure to forced ethanol (10%, v/v) solution. Both groups exhibited large increases (> 2X) in daily fluid intake (DFI) when saccharin (0.1%, w/v) was present and exhibited moderate levels of ethanol intake. Only the P rats significantly increased their ethanol consumption after exposure to ethanol as the sole drinking fluid. Correlational analyses revealed that the absolute intakes of saccharin and ethanol were not significantly correlated in either group, but the increase in DFI in the presence of saccharin was highly correlated with ethanol intake after forced ethanol exposure (r > +0.8; p < 0.05). Similarly, when correlations were conducted for these variables over both the P and FH groups, the correlation between increase in DFI in the presence of saccharin and alcohol intake was significantly higher than that between saccharin and alcohol intakes. Reexamination of previous data from 6 different rat strains also revealed a significant correlation between increase in DFI in the presence of saccharin and ethanol intake. These findings suggest that the dramatic increase in of DFI in the presence of saccharin may be an animal analog of the clinical phenomenon known as a loss of control.

Effects of chronic mild stress on serum complement activity, saccharin preference, and corticosterone levels in Flinders lines of rats

Complement proteins and fragments participate in the induction and modulation of specific and nonspecific immune reactions. We have examined the effect of 4 weeks of chronic mild stress (CMS) on complement sheep red blood cell hemolytic activity measured in CH50 units in two selectively bred lines of rats, the Flinders resistant line (FRL) and the Flinders sensitive line (FSL), that differ in cholinergic sensitivity and behavioral characteristics. Additionally, CMS-induced hedonic deficit (decreased preference for 0.02% saccharin over water) and serum corticosterone levels were compared in FRL and FSL rats. CMS caused a significantly (p < 0.01) greater decline in CH50 responses in FSL (-15%) than in FRL (-7%) rats. This was accompanied by a significant (p < 0.01) suppression of saccharin preference over a 24 h period in both FRL and FSL rats. Both lines showed a similar, more than 2-fold (p < 0.01) increase in corticosterone levels following CMS. These results further confirm that CMS induces a depressive-like state in rats as well as the validity of the FSL rat as a genetic model of depression. They also indicate that the effect of stress on the immune system can be monitored by measuring the complement CH50 response.

Is cholinergic sensitivity a genetic marker for the affective disorders?

The recent literature on the involvement of cholinergic muscarinic mechanisms and adrenergic/cholinergic balance in affective disorders is reviewed and integrated with the older literature. There is strong evidence supporting the presence of exaggerated responses (behavioral, neuroendocrine, sleep) to cholinergic agents in affective disorder patients relative to normal controls and certain other psychiatric patients. There is also some, albeit less, conclusive evidence that these exaggerated responses may occur in euthymic individuals with a history of affective disorders, or in children at risk for development of affective disorders. Despite these promising results, suggesting a role for acetylcholine in the genetics of the affective disorders, further work in biochemistry and genetics is needed to link specific muscarinic receptors or other cholinergic variables to affective illness.

Swim test immobility co-segregates with serotonergic but not cholinergic sensitivity in cross-breeds of Flinders Line rats

The Flinders Sensitive Line (FSL) rat, a genetic animal model of depression, was cross-bred with its normal control, the Flinders Resistant Line (FRL) rat, in order to investigate the relationship between cholinergic sensitivity, the selected variable, and two apparent genetically correlated variables, serotonergic sensitivity and swim test immobility. Cross-breeding established F1, F2 and back-cross progeny, with at least 20 rats of each sex for each group. Cholinergic sensitivity was assessed as the hypothermic response to oxotremorine (0.2 mg/kg) in 30 day old rats. Serotonergic sensitivity was assessed as the hypothermic response to 8-OH-DPAT, a serotonin (5-HT)-1A agonist, in 35-40 day old rats. Immobility was assessed as the time spent immobile in a 5 min swim test in 60-70 day old rats. For each variable, there were highly significant group differences, with the parental FSL and FRL groups being at the extremes. The segregating populations tended to be intermediate between the parental lines and were generally significantly different from both FSL and FRL groups. However, the crosses more closely resembled the FRL parent for only the cholinergic responses, the distributions for 8-OH-DPAT and immobility suggesting predominantly additive genetics. Statistical analyses with chi square to compare response distributions and regression to quantify the association between variables in the segregating populations confirmed that cholinergic sensitivity was different from serotonergic sensitivity and immobility, which were significantly correlated with each other.(ABSTRACT TRUNCATED AT 250 WORDS)

Rapid selection for serotonin-1A sensitivity in rats

National Institutes of Health (NIH) heterogeneous stock (HS) rats were obtained and genetically selected for either larger (HI line) or smaller (LO line) hypothermic responses to the selective serotonin-1A (5-HT1A) agonist 8-hydroxy-2-(di-N-propylamino)tetralin (8-OH-DPAT). A randomly bred (RA) control line was also bred in parallel. There was a rapid response to selection, with HI and LO S1 progeny already showing significantly different hypothermic responses to DPAT. The data for the S3 progeny indicated that selection was proceeding in both directions, with the hypothermic responses of the LO line being about 0.5 degrees C less than that of the RA line (p < 0.01) and the hypothermic response of the HI line being about 0.7 degrees C greater (p < 0.01). The selected lines also differed in their hypothermic responses to the cholinergic agonist oxotremorine, but these differences did not change with further selection. These findings indicate that selection for 5-HT1A sensitivity may occur quite rapidly and that changes in muscarinic sensitivity do not parallel those changes in serotonergic sensitivity.

Chronic mild stress-induced anhedonia: greater effect in a genetic rat model of depression

The effects of acute and chronic stressors on saccharin intake and preference in the hypercholinergic Flinders Sensitive Line (FSL) rat, a putative genetic animal model of depression, were studied and compared to the control Flinders Resistant Line (FRL) rats. Overall, the FRL rats drank significantly less saccharin and water than the FSL rats when compared over a wide range of saccharin concentrations (0.01-5%) under baseline conditions. A 0.02% saccharin concentration was used in subsequent experiments. We observed a significant suppression of saccharin intake/preference at 1 h following a single 5-min exposure to cold swim stress only in FSL rats. There was a tendency to increase saccharin intake in both lines at 1 h following a scrambled foot shock stress. These effects of acute stressors disappeared upon retesting for saccharin consumption/preference 23 h after the stress. Chronic 4-week exposure to unpredictable mild stressors significantly (p < 0.01) decreased saccharin consumption in the FSL rats, but not in the FRL rats. The FSL rats also exhibited a significantly greater decrease in saccharin preference (-24% vs. prestress baseline, as compared to -7% in FRL controls, p < 0.05). In conclusion, FSL rats appear more prone than the FRL rats to chronic, as well as immediate acute, stress-induced anhedonic effects. This outcome further supports the notion that the FSL rat is a useful model of a genetic predisposition to depressive-like reactions.

Verapamil suppresses d-amphetamine-induced place preference conditioning

The effect of pretreatment with (+/-)-verapamil (5, 10 or 15 mg/kg, i.p.) on place preference induced with d-amphetamine (1 mg/kg, i.p. 40 min after verapamil) was studied in male rats. Place preference conditioning was performed using two-compartment shuttle boxes and 8 alternating stimulant/saline sessions. Verapamil dose-dependently suppressed amphetamine-induced place preference. No significant changes in place preference were observed following 8 alternating verapamil (no stimulant)/saline sessions, irrespective of whether verapamil injections were paired with the originally less or the originally more preferred compartment. It appears that verapamil effectively suppresses the reinforcing properties of d-amphetamine in the paradigm used.

Saccharin intake predicts ethanol intake in genetically heterogeneous rats as well as different rat strains

Saccharin and ethanol intakes were measured in seven strains of rats known to differ in their preferences for ethanol: The Fawn-Hooded (FH), alcohol-preferring (P) and Maudsley Reactive rats have been reported to drink ethanol voluntarily, whereas the alcohol-nonpreferring, Maudsley Nonreactive and Flinders Line (FSL and FRL) rats do not. Saccharin and ethanol intakes were highly correlated (r = +0.61) over all strains, with the FH rats drinking the most of both solutions. Correlation coefficients between pairs of drinking versus nondrinking rat strains were even higher. In a second experiment, genetically heterogeneous F2 progeny from cross-breeding the ethanol-preferring FH rats with the ethanol-nonpreferring Flinders Resistant Line (FRL) rats were studied. The results indicated a high positive correlation between saccharin and ethanol intakes (+0.65). These findings suggest that the association between saccharin and ethanol intakes previously reported in rat strains with different preferences for ethanol may have a similar genetic basis.

Maudsley reactive and nonreactive rats differ only in some tasks reflecting emotionality

The behavior of Maudsley reactive and nonreactive rats, along with that of Wistar controls, was studied using three behavioral tasks which have been associated with emotionality. Consistent with the hypothesis that they are more emotional, the Maudsley reactive rats were more immobile in the forced swim test and spent less time in the open arms of an elevated plus maze than the Maudsley nonreactive or Wistar control rats. However, they learned a two-way active avoidance task just as well as the other two groups. These findings suggest that emotionality is heterogeneous and/or that it is involved to different degrees in the three behavioral tasks.

Genetic animal models of depression and ethanol preference provide support for cholinergic and serotonergic involvement in depression and alcoholism

The present article summarizes some comparative studies of the Fawn-Hooded (FH) rat, a potential animal model of ethanol preference, and the Flinders Sensitive Line (FSL) rat, a potential animal model of depression. Both FH and FSL rats exhibit high degrees of immobility in the forced swim test and have difficulty learning a two-way active avoidance task. However, there were no differences between the FH and FSL rats in the elevated plus maze. Studies of ethanol preference indicated high rates of ethanol intake (greater than 4 g/kg) and preference (greater than 50%) in the FH rats, but low rates of ethanol intake (less than 1.1 g/kg) and preference (less than 20%) in FSL rats. It is concluded that the FSL rats exhibit behaviors consistent with their being an animal model of depression, whereas the FH rats exhibit features consistent with their being an animal model of both depression and alcoholism. Psychopharmacological challenges indicated that both FSL and FH rats were more sensitive to the hypothermic effects of oxotremorine, a muscarinic agonist. However, FSL rats were also more sensitive to serotonergic agonists, and some of the present results and other investigators have reported serotonergic subsensitivity in the FH rats. Thus, FSL rats exhibit both cholinergic and serotonergic supersensitivity, whereas FH rats exhibit cholinergic supersensitivity but normal or reduced serotonergic sensitivity. Progeny from a genetic cross between FH and FSL rats exhibit cholinergic supersensitivity and have high ethanol preference scores. These data are consistent with genetic models suggesting that ethanol preference may be influenced by dominant genes, whereas cholinergic sensitivity may be influenced by recessive genes.

Psychological aspects of premenstrual syndrome. I: Cognition and memory

Fourteen women with PMS and ten without PMS were evaluated with a battery of neuropsychological tests during the follicular and late luteal phases of two consecutive menstrual cycles. Classification was determined with NIMH diagnostic criteria and prospective record keeping. The results indicated that (1) the PMS women had significant difficulty in learning new material and this problem was not phase-dependent, (2) both groups performed better on a test of frontal lobe function during the follicular phase, and (3) mood did not account for any of the differences in cognitive functioning.

Attenuation of alcohol preference in alcohol-preferring rats by a novel TRH analogue, TA-0910

Experiments were performed to characterize the acute effect of different doses of a novel thyrotropin-releasing hormone (TRH) analogue (TA-0910) on ethanol intake in rats. Selectively bred alcohol-preferring (P) rats received a single intraperitoneal injection of normal saline or 0.083, 0.25 and 0.75 mg/kg of TA-0910 at 9:30 AM, and their consumption of ethanol, water, and food was measured for 24 hr. TA-0910 dose-dependently attenuated ethanol intake and commensurately increased water consumption. Only the highest dose of TA-0910 increased the total caloric intake. TA-0910 did not affect the pharmacokinetics of ethanol. These findings indicate involvement of TRH systems in ethanol preference and suggest that centrally acting TRH analogues may be therapeutic in the treatment of alcoholism.

Ethanol and complement hemolytic activity of selectively bred hypercholinergic rats

Depression and alcoholism are associated with impaired immune responses. Complement proteins and fragments participate in the induction and modulation of both specific and non-specific immune reactions. This study examined the effect of prolonged ethanol ingestion on complement CH50 levels in two strains of rats, the Flinders Resistant Line (FRL) and the Flinders Sensitive Line (FSL), that differ in cholinergic sensitivity and depressive tendencies. Chronic ethanol exposure given as either the source of drinking fluid or as a liquid diet had a significant inhibition on mean CH50 unit responses in both FSL (41-48%) and FRL (23-24%) rats. The difference in group response to ethanol was confirmed by a significant interaction of ethanol treatment versus group in the two-way ANOVA. The FSL rats appear to be more easily affected than FRLs. Genetic differences in the neurotransmitter systems, therefore, may play a role in susceptibility to immunosuppression resulting from ethanol exposure.

Suppression of alcohol and saccharin preference in rats by a novel Ca2+ channel inhibitor, Goe 5438

The effect of the novel 1,4-dihydronaphthyridine Ca2+ channel inhibitor Goe 5438 (CI-951) on voluntary ethanol consumption was examined in selectively bred alcohol-preferring (P) rats in a free choice two bottle preference test versus water. Intraperitoneally injected Goe 5438 dose-dependently (5, 10 or 20 mumol/kg, twice daily) inhibited ethanol and increased water intake over the 24 h period (injection day). The drug decreased ethanol preference, originally above 90%, by 6%, 19% and 45% at respective doses, on the injection day. That inhibitory effect of the highest dose of Goe 5438 on ethanol preference remained significant also on days 2 and 3 after injections (-51% and -18%, respectively). Goe 5438, in the highest dose, also tended to decrease granulated chow consumption during the injection day only. To further test whether the inhibition of ethanol preference is secondary to decrease in reinforcing properties of ethanol and not due to interference with satiety mechanisms, we compared the effect of two higher doses (10 and 20 mumol/kg, intraperitoneally, twice daily) of Goe 5438 on spontaneous preference for a non-caloric 0.04% saccharin solution in Sprague-Dawley rats. We observed a dose-dependent suppression of preference (by 44% and 58%, respectively) during the injection day, but not the subsequent 24 h period. However, Goe 5438 also significantly alleviated food pellet intake on the injection day. In conclusion, Goe 5438 produces potent and long-lasting inhibition of voluntary ethanol consumption, which may be secondary to attenuation of reinforcing properties of ethanol.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of calcium channel inhibitors on the hypothermic response to oxotremorine in normo and hypercholinergic rats

The Flinders Sensitive Line of rats (FSL) has been selectively bred to have increased sensitivity to cholinergic drugs. Typically, these rats react with twice as great a hypothermic effect to muscarinic agonists such as oxotremorine, as do similarly bred Flinders Resistant Line rats (FRL). We compared the effects of three chemically different calcium channel inhibitors (diltiazem, nicardipine and verapamil) on the hypothermia induced in FRL and FSL rats by oxotremorine (0.2 mg kg-1 s.c.). Each drug was injected i.p. in a dose of 20 mumol kg-1 30 min before oxotremorine. Methylatropine (2 mg kg-1 s.c.) was administered 15 min before oxotremorine to block the peripheral effects of the agonist. The hypothermic effect of oxotremorine in FSL rats was antagonized by nicardipine and diltiazem. In contrast, verapamil failed to influence the hypothermic response in FSL rats. Verapamil significantly (P less than 0.05) augmented oxotremorine hypothermia in FRL rats. Diltiazem and nicardipine were without effect on oxotremorine-induced hypothermia in FRL rats. There were no significant changes in temperature in separate groups of FRL and FSL rats treated with calcium channel inhibitors alone.

Decreased hyperthermic effect of MK-801 in selectively bred hypercholinergic rats

The Flinders Sensitive Line (FSL) of rats has been selectively bred to have increased sensitivity to cholinergic agonists. However, these rats exhibit altered responsiveness to a number of noncholinergic agents, such as apomorphine, buspirone and ethanol. This study compared the FSL and control Flinders Resistant Line (FRL) rats in terms of their hyperthermic response to the phencyclidine (PCP) receptor agonist, MK-801 (0.2 mg/kg SC) and their MK-801 binding characteristics. We have found that FSL rats react with a delayed hyperthermia, having a significantly lower hyperthermia for the first 120 min of observation. Thereafter the response does not differ in FSL and FRL rats. Both groups had similar affinities and numbers of [3H]MK-801 binding sites in the hippocampus/cerebral cortex. Pretreatment with scopolamine (1 mg/kg SC) failed to affect MK-801-induced hyperthermia in either line of rats. These findings suggest that selective breeding of FSL rats attenuated the secondary mechanisms involved in the PCP receptor-mediated hyperthermic response. However, by itself cholinergic supersensitivity does not appear to be a major factor in the blunted responsiveness of FSL rats to MK-801.

Alterations in the hypothalamic-pituitary-adrenal axis in a proposed animal model of depression with genetic muscarinic supersensitivity

Rats from the Flinders Sensitive Line (FSL) and Flinders Resistant Line (FRL), which have been bred for differences in sensitivity to cholinergic agonists, were killed by decapitation under quiet, nonstressful conditions and the concentrations of corticotropin-releasing factor (CRF) in various brain regions, the concentrations of CRF receptors in the anterior pituitary, and plasma ACTH and corticosterone concentrations were determined. A first study revealed that the cholinergically hypersensitive FSL rats exhibited lower concentrations of CRF in the median eminence, locus ceruleus, and prefrontal cortex, but no such changes in some 13 other brain regions. In this first study, the FSL rats had significantly lower plasma ACTH concentrations. However, there were no differences in plasma corticosterone concentrations between the two groups. A second study confirmed the results of the first study and revealed that the density of anterior pituitary CRF receptor binding sites was elevated in the FSL rats. The observed pattern of alterations in these measures of HPA axis activity suggest that the cholinergically supersensitive FSL rats may possess diminished HPA activity.

Effect of calcium-channel blockers on alcohol consumption in alcohol-drinking monkeys

Experiments were performed to determine the effect of the calcium-channel blockers verapamil and diltiazem on ethanol preference in monkeys. Two days of administration of 10 mg/kg verapamil but not diltiazem or saline significantly decreased ethanol intake in all monkeys tested. Chronic treatment with verapamil, but not saline, dose-dependently attenuated alcohol intake, without significantly influencing water intake. These findings suggest that verapamil exerts an inhibitory action on ethanol preference in chronically alcohol-drinking monkeys, possibly by interfering with Ca(2+)-channels and/or by interacting with the activity of certain central neurotransmitters.

Effect of verapamil on submissive behavior in genetically bred hypercholinergic rats in a water competition test

Male hypercholinergic FSL (Flinders Sensitive Line) and control FRL (Flinders Resistant Line) rats were placed on a water deprivation schedule and tested for dominance behavior with FSL/FRL pairs competing for water. FSL rats spent significantly less time drinking than their FRL partners. Acute injection of 10 mg/kg of verapamil, a calcium channel inhibitor, to FSL rats markedly increased their drinking time without influencing water intake in individually tested rats. This effect of the drug was no longer seen after prolonged 4 day treatment. It is suggested that submissiveness of FSL animals in the water competition test might be due to increased fear which is alleviated by verapamil treatment. Tolerance seems to develop to this effect of the drug.

Effects of bright light on responsiveness to a muscarinic agonist in rats selectively bred for endogenously increased cholinergic function

The Flinders Sensitive Line (FSL) was derived from the Sprague-Dawley rat by selectively breeding those animals exhibiting a high level of sensitivity to an anticholinesterase. The Flinders Resistant Line (FRL) was simultaneously developed as a control line. These lines exhibit nonoverlapping distributions of their thermic responsiveness to oxotremorine. Bright light prevents the development of supersensitivity to oxotremorine occurring as a result of forced stress or treatment with a muscarinic receptor antagonist in the rat. The authors now report that treatment with bright light during the regular photoperiod (i.e., a time that does not produce a phase-shift or free-running) differentially affects the hypothermic response and activity-suppressing effect of oxotremorine in both the FSL and FRL. Both lines exhibit decreased hypothermia without reduction in motor activity in response to oxotremorine following 6 days of treatment with bright light. The magnitude of blunting of the hypothermic response was greater in the FSL than the FRL. These findings suggest that (1) studies of the effects of bright light are contingent on the end point one measures and (2) the capacity of this treatment to blunt the hypothermic response to a muscarinic agonist is greater in an animal model with endogenously hyperactive muscarinic cholinergic systems.

Pilocarpine, an orally active muscarinic cholinergic agonist, induces REM sleep and reduces delta sleep in normal volunteers

The effect of oral pilocarpine, a direct-acting muscarinic, cholinergic agonist, on polygraphic sleep parameters was studied in 13 healthy male volunteers. Subjects received placebo and oral pilocarpine (25 mg) in a double-blind, counterbalanced, crossover design. Pilocarpine shortened the latency of rapid eye movement (REM) sleep and increased total REM time, REM%, and the duration of the first REM period. In addition, it reduced Stage 4 sleep and Delta sleep. Pulse rate was not significantly changed during the first hour of darkness after administration of pilocarpine. Subjective sleep experience and the subjects' condition in the morning were not altered. These results suggest that pilocarpine has central effects (i.e., induction of REM sleep) that are similar to those of other centrally acting muscarinic cholinomimetic agents.

Impaired active avoidance responding in rats selectively bred for increased cholinergic function

It was found that the Flinders Sensitive Line (FSL) of rat, selectively bred for increased cholinergic function, performed poorly in a tone-cued two-way active avoidance task in comparison with the control Flinders Restraint Line (FRL) of rat. These findings are consistent with the suggestion that the FSL rats may be a genetic animal model of depression.

MK-801 potently inhibits alcohol withdrawal seizures in rats

The ability of MK-801, an N-methyl-D-aspartate (NMDA)-channel antagonist, to suppress alcohol withdrawal seizures generated audio-genically was studied in adult male rats using a cross-over experimental design. MK-801 treatment reduced overall seizure score and proportion of rats seizing. In comparison to other seizure models, alcohol withdrawal seizures seem to be particularly sensitive to MK-801, suggesting that mechanisms which result in seizure susceptibility after withdrawal of chronic ethanol exposure may be dependent upon sensitization or upregulation of NMDA processes.

Enhanced affective aggression in genetically bred hypercholinergic rats

Affective aggression was studied in pairs of Flinders Sensitive Line hypercholinergic rats (FSL) and Flinders Resistant Line (FRL) rats in shock-induced and apomorphine-induced fighting tests. FSL rats were significantly more aggressive in both tests. They had higher pain threshold, assessed by the jump-flinch method, than FRL rats. It is concluded that genetically developed cholinergic system supersensitivity has resulted in enhanced responsiveness to stimuli eliciting affective aggression.

Selective antagonistic effects of exposure to bright light on the hypothermic action of ethanol

Flinders Sensitive and Resistant Lines of rats, which are differentially sensitive to the hypothermic effects of both muscarinic agonists and ethanol, were exposed to full spectrum artificial bright light for eight days, because exposure to bright light has been shown to blunt hypothermic responses to muscarinic agonists. There was a selective blunting of the hypothermic effects of ethanol, but no significant change in the intoxicating effects of ethanol, as measured by evaluation of the righting reflex. The selective effect of exposure to bright light on the hypothermic actions of ethanol suggests that bright light may be modifying the function of only a limited number of brain regions, including the hypothalamus.

Decreased alcohol consumption by verapamil in alcohol preferring rats

1. Calcium channel blockers have been proposed, in addition to inhibiting the influx of Ca++ into the cells, to possess a wide variety of pharmacological effects, including interference with certain neurotransmitters involved in mood, mental disorders and alcohol craving. Further, it has been documented that certain neurotransmitters are involved in alcohol craving both in animals and humans. 2. To investigate the effects of Ca(++)-channel antagonist on alcohol preference, verapamil in three doses (5, 10 and 15 mg/kg) was injected (S.C.) twice daily over a period of one day in alcohol-preferring (P) and alcohol non-preferring (NP) rats at 9:00 a.m. and 4:00 p.m. 3. Water, alcohol and food intake were monitored. 4. Our results show that verapamil in doses of 10 and 15 mg/kg significantly (p less than 0.02 and 0.01, respectively) reduced the intake of ethanol and increased the intake of water by P rats. However, injection of an equal volume of saline did not change the pattern of alcohol intake. 5. These results suggest that a (++(+)-channel blocker such as verapamil, could, at least partially, attenuate alcohol preference in alcohol preferring rats. It is possible that verapamil exerts an inhibitory effect on alcohol preference by interfering with Ca++ channels, blocking serotonin uptake or through another mechanism(s).

Behavioral hyporeactivity to physostigmine in detoxified primary alcoholics

Changes in anergia/inhibition, mood, and pulse rate induced by intravenous physostigmine were significantly less pronounced in 26 patients with primary alcoholism than in 36 normal control subjects. These results suggest possible abnormalities in central cholinergic functioning in primary alcoholics.

Effects of brief naps on mood and sleep in sleep-deprived depressed patients

To determine the effects of brief naps on mood and electroencephalographic (EEG) sleep in sleep-deprived depressed patients, data from 19 hospitalized patients with depression were analyzed; all were kept awake from 0700h until the following day, when they were allowed 10-min naps at either 0830h or 1500h. Six of the patients showed a clinically significant improvement (greater than 40% change) on the Hamilton Rating Scale for Depression (HRSD) before the nap after all-night sleep deprivation, and the group as a whole showed a significant improvement on the HRSD, the Profile of Mood States, and the Brief Psychiatric Rating Scale subscale for depression. Naps did not alter mood in the responders, but did improve measured depression on the HRSD in the non-responders. Morning and afternoon naps did not differ significantly in their effects on mood or nap sleep. On the recovery sleep, patients who were classified as responders after the nap showed a significantly greater increase in delta (Stage 3 + 4) sleep compared with baseline than nonresponders.

Biological effect of bright light

1. Five minute bright light exposures reduced plasma levels of melatonin in eight normal subjects. 2. No significant change in ACTH levels occurred. 3. These results raise the possibility that short intense light exposures can synchronize circadian rhythms as well as benefit patients with seasonal affective disorder. They also indicate that short pulses of bright light do not affect pituitary ACTH production.