Effect of yohimbine on plasma homovanillic acid in panic disorder patients and normal controls.

The effects of oral yohimbine (20 mg) or placebo or both drugs on plasma homovanillic acid (HVA) were evaluated in patients with panic disorder and normal controls. Panic disorder patients had similar HVA values at baseline compared with normal controls, and yohimbine failed to produce appreciable changes in HVA in both groups. These findings are discussed within the context of catecholaminergic theories of panic disorder.

Multiplicity of depressive episodes: phenomenological and neuroendocrine correlates.

Sixty-four patients with a Research Diagnostic Criteria (RDC) diagnosis of major depressive disorder were categorized into three groups based on their number of depressive episodes (DE): Gr I (1 DE), n = 16, Gr II (2-4 DE), n = 25; and Gr III (5 or more DE), n = 23. All patients were nonsuppressors after 1 mg dexamethasone suppression test (DST) prior to the start of treatment. Patients were monitored during the course of their treatment using serial Hamilton Depression scores and post-DST plasma cortisol levels. A proportionately equal number of patients in the three groups had a favorable outcome, i.e., the number of depressive episodes did not predict recovery. Despite favorable clinical outcome, patients with higher numbers of depressive episodes had significantly higher post-DST plasma cortisol levels that were above the suppressive range (greater than 5 micrograms/dl). Patients with a higher number of depressive episodes had a significantly shorter duration of index episode and were younger at first depressive episode than patients in the other two groups. These results, however, were confounded with polarity, with a higher number of bipolars in Gr III than in the other two groups. Results are discussed in light of phenomenological and psychoendocrine findings of earlier studies.

Multiple depressive episodes and plasma postdexamethasone cortisol levels.

The hypothalamic-pituitary-adrenal (HPA) axis is dysregulated in many patients with major depressive disorder (MDD). To determine whether or not a past history of depressive episodes is associated with this dysregulation, we studied the relationships among number of past depressive episodes, number of previous hospitalizations for depression, and number of years since first depressive episode and biological markers of depression (postdexamethasone plasma cortisol levels and dexamethasone suppressor/nonsuppressor status). No significant relationships were detected.

Alpha 2-adrenoreceptor status in obsessive-compulsive disorder.

Ten patients with obsessive-compulsive disorder (OCD) and 13 normal control subjects received intravenous infusions of 2 X 10(-6) g/kg of clonidine and normal saline on separate days. Responses to the drug relating to plasma growth hormone (GH), 3-methoxy-4-hydroxyphenylglycol (MHPG), heart rate, blood pressure, and several symptoms were determined. Additionally, platelet alpha 2-adrenoreceptor binding was measured in most of the subjects. GH, MHPG, blood pressure, and heart rate responses to clonidine did not differ between groups. As expected, patients reported more symptoms than normal subjects, and clonidine was sedating for both groups. Patients did not differ from normal subjects in the symptom response to clonidine. The maximum number of binding sites (Bmax) for tritiated clonidine was significantly greater in OCD patients than in normals. This pattern of alpha 2-adrenoreceptor status is different than the patterns in major depression and panic anxiety.

Adrenergic receptors in premenstrual dysphoric disorder: I. Platelet alpha 2 receptors: Gi protein coupling, phase of menstrual cycle, and prediction of luteal phase symptom severity.

BACKGROUND: Abnormal alpha 2-adrenergic receptor (AR) function is implicated in anxiety and depressive disorders. Premenstrual dysphoric disorder (PMDD) is characterized by anxiety and depressive symptoms, which may be associated with changes in alpha 2AR function. Previous studies on alpha 2AR function during phases of the menstrual cycle in controls and PMDD patients are inconsistent. METHODS: alpha 2AR function was examined in 16 PMDD patients and 15 controls during the follicular phase, and in 10 PMDD patients during late luteal phase. Antagonist-measured maximum binding capacity, agonist-measured receptor density in high- and low-conformational states, and agonist affinity to both states were measured. Coupling efficiency to Gi protein was estimated. RESULTS: There were no significant differences in coupling efficiency. PMDD patients had significantly low antagonist affinity; there were no differences in other binding parameters. There were no changes in alpha 2AR binding parameters between phases of menstrual cycle in PMDD women. alpha 2AR density and symptom severity were inversely related during the follicular phase in controls and patients. During luteal phase, alpha 2AR density correlated positively with symptom severity in patients. High follicular alpha 2AR density predicted more severe luteal symptoms in PMDD patients. CONCLUSIONS: These findings are discussed in view of the molecular biology of alpha 2AR, and their role in PMDD, anxiety, and depressive disorders.

Biogenic amines distribution in the brain of nervous and normal pointer dogs. A genetic animal model of anxiety.

Nervous pointer dogs have been suggested as an animal model for pathological anxiety. In order to study possible disturbances in neurotransmitter functions in this animal model, we measured brain biogenic amines (norepinephrine, dopamine, and serotonin) and their metabolites in both nervous and normal dogs. Eight nervous and six normal dogs were behaviorally tested and later anesthetized and killed. Brains were removed and dissected while frozen using a punch technique. Samples were assayed using high-performance liquid chromatography (HPLC) with electrochemical detection. The nervous dogs had higher [NE] in the reticular formation and lower serotonin, and its metabolite 5-hydroxyindoleacetic acid, in the septal nuclei, indicating possible important differences in noradrenergic and serotonergic functions in the nervous dogs. There was a trend for lower [HVA] and [DOPAC] levels and a significantly lower [DOPAC]/[DA] ratio in the nervous dogs, suggesting decreased dopaminergic function.

Beta-adrenoreceptor coupling to GS protein in alcohol dependence, panic disorder, and patients with both conditions.

Ethanol may downregulate G-protein-coupled beta-adrenoreceptors (beta AR). beta AR may also be dysregulated in panic disorder (PD). In clinical samples, many patients have comorbid alcohol dependence (AD) and PD. Therefore, we investigated beta AR coupling in patients with these disorders. We harvested polymorphonuclear leukocytes from 24 healthy volunteers (Vs), and from 22 abstinent AD patients, 7 PD patients, and 9 patients with comorbid AD/PD. beta AR were assayed using saturation and agonist-displacement experiments. Group differences were tested using one-way analysis of variance (ANOVA). All beta AR binding parameters were similar in AD patients and Vs. The ratio of the agonists' dissociation constant from the receptor in the low affinity state (KL) to that in the high affinity state (KH) was significantly higher in PD patients than in AD patients and Vs (930.97 +/- 440.80 vs. 226.2 +/- 94.47 vs. 197.05 +/- 61.03, respectively, p < .01). This finding suggests that beta AR are supercoupled to GS in patients with PD. There was a trend for higher total receptor density (RT) in AD/PD and PD patients (Vs = 39.06 +/- 42.57 vs. AD = 27.93 +/- 23.07 vs. AD/PD = 66.85 +/- 79.02 vs. PD = 68.36 +/- 49.20, p < .08). There were no differences between AD/PD and PD patients, who combined had a significantly higher RT than Vs and AD patients (Vs = 38.95 +/- 8.81 vs. AD = 29.63 +/- 5.07 vs. AD/PD = 67.51 +/- 17.00, fmol/mg protein, p < .04). Finally, AD/PD patients had a significantly higher receptor density in the low-affinity conformational state than Vs and AD patients, but not PD patients (25.96 +/- 11.59 vs. 10.69 +/- 1.53 vs. 7.62 +/- 1.08 vs. 17.07 +/- 5.26 fmol/mg protein, respectively, p < .005). beta AR function in polymorphonuclear leukocytes is normal in abstinent alcoholics. The previously reported abnormal beta AR regulation in alcoholism may be state dependent. The higher RT and KL/KH ratio in AD/PD and PD, but not in AD patients, suggest that increased beta AR function may be important in the pathophysiology of PD.

Adrenergic receptor function in panic disorder. I. Platelet alpha 2 receptors: Gi protein coupling, effects of imipramine, and relationship to treatment outcome.

Various studies suggest alpha 2-adrenergic receptor (alpha 2AR) dysregulation in panic disorder (PD). Platelet alpha 2-AR exist in high- and low-conformational states as a function of their coupling to Gi protein. alpha 2AR coupling is important in signal transduction and is modulated by antidepressants. alpha 2AR density in the high- and low-conformational states, agonist affinity, and coupling efficiency were investigated in 21 healthy controls, 21 drug-free PD patients, and eight imipramine-treated patients using norepinephrine displacement of 3H-yohimbine binding. Percentage of receptors in the high-conformational state (%RH) and the ratio of the agonist dissociation constant to the receptor in the low-/high-conformational state (KL/KH), calculated from displacement experiments, were used as coupling indices. Patients had high alpha 2AR density in both conformational states. %RH and KL/KH ratio were significantly different, particularly in patients with Hamilton scale for depression (HAMD) scores > or = 15. Imipramine treatment (29 weeks) had no effect on alpha 2AR density or coupling, despite improvement in anxiety ratings. High pretreatment alpha 2AR density and coupling predicted low severity of anxiety after treatment. Increased alpha 2AR density and abnormal coupling may represent an adaptive mechanism or trait marker in PD.

Evidence for hypothalamo-growth hormone dysfunction in panic disorder: profile of growth hormone (GH) responses to clonidine, yohimbine, caffeine, glucose, GRF and TRH in panic disorder patients versus healthy volunteers.

Given the abrupt and time-limited nature of daytime-awake and nocturnal-sleep panic attacks, several chemical and neuroendocrine challenge tests have been employed to investigate the neurobiology of "spontaneous" panic attacks. Previously we demonstrated that panic disorder patients have blunted growth hormone (GH) responses to clonidine, an alpha 2-adrenergic agonist. However, the mechanism of this blunted response and the role of hypothalamic-GH dysfunction, if any, remains unclear. To further delineate the status of hypothalamic-GH function in panic disorder, we review the literature and present original data on the GH responses to a number of different chemical and neuroendocrine challenge paradigms. Although stress-mediated increases in GH are thought to be a common correlate of stress in humans, our findings indicate that panic disorder patients have significantly blunted GH responses to clonidine, yohimbine, growth-hormone releasing factor, and caffeine compared to normal control subjects. A similar trend was noted in the delayed rise in GH after glucose challenge. There was no difference in the rate of abnormal GH responses to thyrotropin-releasing hormone in panic disorder compared to normal control subjects. No drug or neuroendocrine challenge, even if associated with marked increases in anxiety, produced a significantly enhanced GH response compared to normal control subjects. These findings provide support for a hyporesponsive hypothalamic-GH system in panic disorder. These observations, combined with preliminary observations from our clinic of short stature in several cases of prepubescent children with anxiety disorders, also underscore the need for assessing early growth patterns in individuals with panic disorder. Strategies for investigating the site(s) of possible neurotransmitter or hypothalamic-GH-somatomedin dysfunction are discussed.

Plasma 3-methoxy-4-hydroxyphenylethylene glycol (MHPG) and growth hormone responses to yohimbine in panic disorder patients and normal controls.

Eleven patients with a DSM-III diagnosis of panic disorder and seven normal controls received yohimbine (20 mg) or placebo orally in a double-blind paradigm on two separate days. Compared to normal control subjects, the panic disorder patients had similar behavioral responses to placebo but a greater anxiogenic response to yohimbine. Compared to placebo, yohimbine produced a significant increase in plasma 3-methoxy-4-hydroxyphenylethylene glycol (MHPG) levels (p less than 0.02), with a trend toward greater MHPG rises in the panic disorder patients compared to the normal controls. In the patients, but not in the controls, there was a significant positive correlation between yohimbine-induced peak changes in MHPG and increased ratings of panic anxiety. Yohimbine had no effect on plasma growth hormone (GH) levels in either patients or controls. These results are discussed within the context of the noradrenergic theory of panic disorder.

Coupling efficiency of brain beta-adrenergic receptors to Gs protein in suicide, alcoholism and control subjects.

Abnormal beta-adrenergic receptor (betaAR) density in the brains of suicide victims has been reported, although results of studies are inconsistent. Ethanol modifies betaAR-mediated signal transduction. Moreover abnormal betaAR function has been implicated in alcoholism. BetaAR antagonists, which were used as ligands in previous betaAR binding studies, also bind to 5-HT1B/1Dbeta receptors; hence, their estimates of betaAR density are confounded by binding to 5-HT1B/1Dbeta receptors. More importantly, previous studies did not examine betaAR agonist affinity or coupling efficiency to Gs protein. We investigated agonist affinity and coupling efficiency of betaAR to Gs protein in the brains of ten suicide victims, six subjects with alcoholism, and eight controls. There were no differences in betaAR density in either the frontal cortex or hippocampus of suicide victims or alcoholic subjects compared to controls. Preliminary results indicate betaAR supercoupling in suicide victims in both brain regions and uncoupling in alcoholic subjects in the frontal cortex. These results are discussed in view of the existing literature on the role of betaAR in suicide and alcoholism and the mechanism of action of antidepressants.

Neutrophil beta2-adrenergic receptor coupling efficiency to Gs protein in subjects with post-traumatic stress disorder and normal controls.

The symptomatology of post-traumatic stress disorder (PTSD) involves sympathetic hyperarousal. Several of these sympathetic symptoms are mediated through end-organ beta2-adrenergic receptors (beta2AR). Increased sympathetic activity in PTSD could therefore be due to increased betaAR function. This study investigated betaAR function in 30 healthy controls and 20 drug-free PTSD patients. BetaAR binding studies were conducted using antagonist-saturation and agonist-displacement experiments. Measures of beta2AR coupling to Gs protein were derived from agonist-displacement experiments. PTSD patients had significantly higher beta2AR density particularly in the high-conformational state and higher beta2AR coupling than controls, as reflected in a higher percentage of receptors in the high conformational state and a higher ratio of the agonist dissociaton constant from the receptor in the low/high-conformational state. Increased betaAR function in PTSD is consistent with the symptomatology of this disorder. Increased betaAR density and coupling may be consistent with downregulation of betaAR density and uncoupling by antidepressants and may underlie their partial efficacy in PTSD. Dysregulation in Gs protein function is postulated and, agonist-mediated regulation of betaAR expression and/or betaAR kinase activity in PTSD should be investigated in future studies.

Platelet alpha2-adrenergic receptor coupling efficiency to Gi protein in subjects with post-traumatic stress disorder and normal controls.

Low platelet membrane alpha2-adrenergic receptor (alpha2AR) density and low basal and forskolin-stimulated cyclic adenosine monophosphate responses, which have been reported in post-traumatic stress disorder (PTSD), suggest either abnormal alpha2AR coupling to G(i) protein or dysregulation in post-receptor signal transduction mechanisms. alpha2AR density in the high- and low-conformational states, agonist affinity in both states and coupling to G(i) protein were investigated in 23 drug-free combat PTSD patients and 25 normal controls. alpha2AR coupling measures were not different between PTSD patients and controls. Total alpha2AR density was higher in PTSD patients than controls, due to a higher density of the receptor in the high-conformational state. There were no differences in agonist affinity to the receptor in either conformational state. Results rule out dysregulation in alpha2AR coupling to G(i) protein. Studies of post-receptor signal transduction mechanisms are warranted.

The relationship between plasma MHPG and NE: employing regression models in estimating centrally derived MHPG and peripheral NE turnover rate in panic disorder.

Studies investigating the role of the noradrenergic system in the pathophysiology of anxiety have focused on measuring plasma 3-methoxy-4-hydroxyphenylethyleneglycol (MHPG) levels. Fewer studies have examined norepinephrine levels. Basal plasma norepinephrine and free MHPG levels were simultaneously measured in 33 normal controls and 20 panic disorder (PD) patients. Norepinephrine levels were similar in patients and controls, but MHPG levels were significantly lower in patients (13.34 +/- 3.22 vs 18.37 +/- 4.49 pmol ml-1, p < 0.0001). Norepinephrine correlated significantly with plasma MHPG levels in controls (r = 0.538, p < 0.0001) and patients (r = 0.645, p < 0.002). Patients had a trend toward a lower y-intercept than controls, suggesting a lower contribution by the CNS to MHPG pool plasma levels (9.18 vs 12.51, p < 0.08). Norepinephrine turnover rate was similar in patients and controls. We propose that the dysregulation in the noradrenergic system in PD may be akin to animal studies of acute-on-top-of-chronic stress paradigms, whereby chronic stress results in normal or decreased basal NE turnover and sensitized responses to recurrent stresses.

Indices of brain beta-adrenergic receptor signal transduction in the learned helplessness animal model of depression.

Both stress response and antidepressant drug action may be mediated by beta-adrenergic receptors (beta AR). Since learned helplessness is a stress-induced animal model of depression, beta AR are relevant to investigate in this model. To date, studies have measured changes in total receptor density (RT), but have not examined more detailed aspects of signal transduction mechanisms such as coupling of the receptor to GS protein. We have investigated brain beta AR coupling in the frontal cortex, hippocampus and hypothalamus of rats exposed to inescapable shock and then tested for learned helplessness, and in both tested and naive controls using [125I]-iodocyanopindolol (ICYP) as the ligand. Both antagonist-saturation and agonist-displacement experiments were conducted, and the specificity for the beta AR was optimized by excluding ICYP binding to 5HT1B receptors. The percentage receptor density in the high-conformational state (%RH) and the ratio of agonist (isoproterenol) dissociation constant from the receptor in the low-/high-conformational states (KL/KH) were used as indices of coupling to GS protein. No significant differences were found between rats developing learned helplessness and non-helpless rats after inescapable stress in any parameter measured in any brain region. In the frontal cortex, exposure to inescapable shock induced beta AR uncoupling from GS protein as suggested by a low KL/KH ratio both in helpless and non-helpless rats but not in either control group. In the hypothalamus, there were trends for higher RL, RT and KL/KH ratio in helpless rats and stressed controls compared to naive controls. These findings suggest that beta AR binding parameters in frontal cortex, hippocampus or hypothalamus did not differentiate between helpless and non-helpless rats. Changes in beta AR coupling observed in these brain regions may reflect effects of stress, which appeared to be region-specific, rather than stress-induced behavioral depression.

Adrenergic receptor function in panic disorder. II. Neutrophil beta 2 receptors: Gs protein coupling, effects of imipramine treatment and relationship to treatment outcome.

Panic attacks are associated with increased autonomic symptoms, suggesting increased beta 2-adrenergic receptor (beta 2AR) function in PD. Tricyclic antidepressants downregulate beta AR function. Previous studies on beta AR function in PD, however, are inconsistent. We recently found increased beta AR coupling and density in neutrophils of symptomatic drug-free PD patients. This study evaluated beta AR coupling to Gs protein in 28 controls, 25 drug-free PD patients and 8 PD imipramine-treated patients. PD patients had significantly higher coupling and receptor density, particularly in the high-conformational state. Differences were more pronounced in patients with less depressive symptomatology. Treatment with imipramine was associated with decreased beta AR coupling and density in the high-conformational state. Several beta AR binding parameters were related to severity of anxiety symptoms and treatment outcome. Antidepressants downregulate beta AR density and induce uncoupling from Gs protein in PD. Future studies may investigate beta AR coupling in relationship to treatment outcome and the role of beta AR kinase in PD.

Effects of chronic exposure to ethanol alone and in combination with desipramine on beta-adrenoceptors of rat brain.

The effect of chronic ethanol exposure alone or in combination with desipramine on agonist and antagonist binding to beta-adrenoceptors was studied in membrane preparations from rat frontal cortex and hippocampus. Ten day exposure of animals to ethanol vapor (25 mg/l) in inhalation chambers had no effect on binding properties of antagonist iodocyanopindolol (ICYP) in either brain region. However, ethanol in combination with chronic desipramine treatment prevented the reduction of beta-adrenoceptor density in frontal cortex produced by desipramine administration. Similar to its effects on antagonist binding, chronic ethanol exposure did not change the agonist isoproterenol binding characteristics measured in membranes from either rat frontal cortex or hippocampus. However, the combination of ethanol plus desipramine reduced the dissociation constant of the low affinity state of the receptor (KL) in frontal cortex from 23.1 +/- 3.7 microM in controls to 11.2 +/- 1.7 microM. Moreover, ethanol plus desipramine produced a greater decrease in the percentage of cortical receptors in the high affinity state for agonist (%RH) than did desipramine alone. This suggests that ethanol enhances desipramine-induced desensitization of beta-adrenoceptors in frontal cortex in spite of the prevention of reduction in density of the receptors. In hippocampal membranes, ethanol together with desipramine prevented desipramine-induced changes in agonist binding characteristics, i.e. the decrease in KH (dissociation constant from high affinity state of the receptor) and the consequent enhancement in KL/KH ratio. Thus, chronic exposure to relatively low concentrations of ethanol partially prevents effects of desipramine on beta-adrenoceptors.

Ten day administration of desipramine produces an increase in KL/KH for beta-receptors in rat hippocampus.

The action of chronic desipramine administration on agonist and antagonist binding to beta-adrenoceptors was investigated in rat frontal cortex and hippocampus. Ten day treatment with desipramine (10 mg/kg per day i.p.) resulted in a significant 34% decrease in the density of beta-adrenoceptors in membranes from rat frontal cortex but not hippocampus. The KD values for antagonist (iodocyanopindolol) did not change in either tissue after the desipramine treatment. Desipramine had no effect on the affinity of the agonist isoproterenol in frontal cortex. The percentage of receptors in the high affinity state for isoproterenol (% RH) decreased by 11% in the membranes from frontal cortex after desipramine administration. In contrast, in hippocampal membranes, desipramine treatment produced a decrease in KH (dissociation constant for isoproterenol binding to the high affinity state) and consequently a 137% increase in the ratio of dissociation constants for isoproterenol to the low and high affinity conformations (KL/KH; an putative index of coupling). This observation is new and suggests possible supercoupling of beta-adrenoceptors in hippocampus during desipramine treatment. Thus, in addition to desensitization of beta-adrenoceptors in rat frontal cortex ten day administration of desipramine causes a change compatible with supercoupling of beta-receptors in hippocampal membranes.

The combined effects of chronic ethanol/desipramine treatment on beta-adrenoceptor density and coupling efficiency in rat brain.

Both ethanol and desipramine influence beta-adrenoceptor regulation. We reported previously that ethanol partially counteracted desipramine's effects on beta-adrenoceptor. Previous studies utilized beta-adrenoceptor radioligands that also bind to 5-HT1B receptors, thus, changes in 5-HT1B receptors could have confounded the results. The effects of chronic ethanol, desipramine and ethanol/desipramine treatment on beta-adrenoceptor coupling efficiency to Gs protein in rat brain were examined using 125I-iodocyanopindolol after blocking binding to 5-HT1B receptors. In the frontal cortex, ethanol uncoupled beta-adrenoceptor from GS. Desipramine decreased beta-adrenoceptor density, particularly in the high-conformational state, with no effect on coupling. In combined treatment, desipramine prevented ethanol-induced uncoupling. In the hippocampus, desipramine enhanced beta-adrenoceptor coupling, but ethanol had no effect. In combination with desipramine, ethanol enhanced desipramine-induced decrease in beta-adrenoceptor density in the high-conformational state, but uncoupled beta-adrenoceptors, an effect not observed with ethanol alone. These results suggest a complex interplay between ethanol and antidepressants in modulating beta-adrenoceptor function.

Neutrophil beta(2)-adrenoceptor function in major depression: G(s) coupling, effects of imipramine and relationship to treatment outcome.

Abnormal beta(2)-adrenoceptor density and beta(2)-adrenoceptor-mediated cyclic adenosine monophosphate (cAMP) responses were inconsistently reported in major depressive disorder. Tricyclic antidepressants downregulate beta-adrenoceptor density and decrease coupling to G(s) protein. Abnormal beta-adrenoceptor coupling may exist in major depressive disorder and may relate to treatment response. We investigated beta(2)-adrenoceptor coupling to G(s) protein in 25 controls, 23 major depressive disorder drug-free patients and 16 major depressive disorder patients after chronic imipramine treatment using agonist displacement experiments. Pretreatment beta(2)-adrenoceptor coupling and density were normal in patients as a whole. Chronic imipramine induced beta(2)-adrenoceptor uncoupling. This effect was observed in treatment responders who had increased beta(2)-adrenoceptor density in the high-conformational state and supercoupling prior to treatment. Beta(2)-adrenoceptor density decreased after imipramine treatment. Treatment non-responders had seemingly normal pretreatment beta(2)-adrenoceptor function, which was not changed by imipramine. Differences in beta(2)-adrenoceptor regulation in major depressive disorder may underlie treatment response. The results indirectly implicate abnormal agonist-mediated beta(2)-adrenoceptor gene expression, protein kinase A, and protein kinase C in major depressive disorder.