Central noradrenergic responsiveness to a clonidine challenge in Generalized Anxiety Disorder: a Single Photon Emission Computed Tomography study

Generalized Anxiety Disorder (GAD) may involve hypo-responsiveness of noradrenaline a2 receptors. To test this hypothesis, we used (99m)Tc-hexa-methyl-propylene-amine-oxime (HMPAO) Single Photon Emission Computed Tomography to measure regional cerebral perfusion in patients with untreated GAD, venlafaxine-treated patients and healthy controls during word generation before and after clonidine. Concurrent psychological and physiological measures supported noradrenergic hypofunction in GAD in some cases. A single-day split-dose technique was used. Images were processed using SPM5 (Institute of Neurology). Factorial analysis revealed no significant results. Exploratory analyses were done. Regional perfusion during verbal fluency differed by group pre-clonidine. Compared with healthy controls, patients with untreated GAD displayed increased perfusion in the left Broca's area and left occipitotemporal region. Treated GAD patients displayed increased cerebellar perfusion bilaterally. Clonidine was associated with different changes in cerebral perfusion in each group. Increases were seen in the right supra-marginal gyrus in healthy subjects, in the left pre-central gyrus in treated GAD patients and in the right cerebellum and middle frontal gyrus in untreated GAD patients. Despite these differences, the findings were not consistent with a noradrenergic hypo-responsiveness hypothesis, as the treated group showed a different pattern of response rather than a normalization of response.

A pilot study of the effectiveness of D-cycloserine during cue-exposure therapy in abstinent alcohol-dependent subjects

RATIONALE

Cue-exposure therapy (CET) has been advocated as a potentially effective treatment of addictive behaviours. Strategies that enhance learning may improve the outcome of CET. D-cycloserine (DCS), a partial N-methyl-D-aspartate receptor agonist, has been shown to facilitate extinction of learned fear in rats and augment exposure-based treatment in some anxiety disorders in man.

OBJECTIVE

This double-blind placebo-controlled pilot study used a cue-exposure paradigm, salient for an individual's alcohol drinking, to see if DCS would reduce cue-reactivity compared with placebo.

METHODS

Sixteen abstinent, alcohol-dependent individuals were randomised to receive either a single-dose (250 mg) DCS or placebo before CET sessions, separated by at least 1 week. Subjective responses were assessed using the Alcohol Urge Questionnaire (AUQ) and visual analogue scales. Cardiovascular responses were assessed using Finapres©.

RESULTS

The cue-exposure paradigm significantly increased craving assessed with the AUQ during the first session. In subsequent sessions, the degree of craving was reduced. However, no significant difference was seen between the DCS and placebo groups in any outcome measure. The variability of responses between individuals was great with more than half the groups reporting no or very small changes in AUQ scores.

CONCLUSION

This is the first human study to our knowledge to assess the efficacy of DCS in facilitating CET in alcohol dependence. The high proportion of subjects with little or no response to cue-exposure would make any effect of DCS very difficult to detect. It is important that future studies carefully consider the criteria for inclusion.

Noradrenergic function in generalized anxiety disorder: impact of treatment with venlafaxine on the physiological and psychological responses to clonidine challenge

Serotonin and noradrenaline reuptake inhibitor (SNRI) antidepressants have evidence of efficacy in the treatment of generalized anxiety disorder (GAD); however, it is not clear whether there is an advantage over selective serotonin reuptake inhibitor (SSRI) medicines and there is limited evidence for noradrenergic dysfunction in GAD. We tested whether a dysfunctional alpha-2 adrenoceptor system is present in patients with GAD and the effects of SNRI treatment on this system. The method used was an infusion of clonidine (a selective alpha-2 adrenergic receptor agonist) on psychological and physiological outcomes in three subject groups: 10 untreated GAD patients, five SNRI-treated GAD patients and seven normal controls. The clonidine challenge elicited sedation, a rise in growth hormone, decrease in blood pressure, decline in saccadic eye movement (SEM) variables, and improvement in verbal fluency as anticipated in the 22 subjects examined. Lower cortisol levels were found in controls and higher blood pressure readings in GAD-treated subjects, as well as evidence that GAD-treated subjects had SEMs that were intermediate between control and GAD subjects' scores and have less clonidine-induced sedation. The implications of these findings with reference to the study hypothesis in this small study are discussed.

Long-term effect of insulin on glucose transport and insulin binding in cultured adipocytes from normal and obese humans with and without non-insulin-dependent diabetes

We have tested the hypothesis that in vitro exposure of insulin-resistant adipocytes with insulin results in improved insulin action. A primary culture system of adipocytes from obese subjects with or without non-insulin-dependent diabetes mellitus (NIDDM) and nonobese control subjects has been developed. The adipocytes when cultured in serum-free medium do not lose their original characteristics in regard to insulin binding and glucose transport. The adipocytes from three groups were incubated with insulin (0, 10(-10) M, and 10(-7) M) for 24 h at 37 degrees C, receptor-bound insulin was dissociated, and basal and insulin (1 X 10(-11)-10(-7) M)-stimulated glucose transport and 125I-insulin binding were determined. The 24-h insulin exposure of adipocytes from control subjects decreased basal and insulin-stimulated glucose transport. The effects of 1 X 10(-7) M insulin were more pronounced than 1 X 10(-10) M insulin. Similarly, insulin exposure decreased insulin sensitivity and responsiveness of cultured adipocytes from obese and NIDDM patients. The insulin-induced reduction in insulin sensitivity and responsiveness for glucose transport in three groups were due to alterations at insulin binding and postbinding levels. In conclusion, insulin induces insulin resistance in control adipocytes and further worsens the insulin resistance of adipocytes from obese and NIDDM subjects. For insulin to improve the insulin resistance of adipocytes from NIDDM patients, either more prolonged in vitro insulin exposure and/or other hormonal factors might be required.