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Updated: May 25, 2026

Disrupting Reconsolidation of Fear Memory in Humans by a Noradrenergic β-Blocker

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Published on: December 18, 2014

Imipramine in panic disorder. 2. Effects on α2-adrenoceptor function.

D J Nutt¹, P Glue

¹University Department of Psychiatry, Warneford Hospital, Oxford, UK.

Journal of Psychopharmacology (Oxford, England)

|January 28, 2012

Summary

Imipramine treatment for panic disorder reduced alpha-2 adrenoceptor sensitivity, indicated by smaller clonidine-induced MHPG, blood pressure, and heart rate changes. These alterations partially explain antidepressant effects in panic disorder.

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Area of Science:

Neuroscience
Psychopharmacology
Clinical Psychiatry

Background:

Panic disorder is associated with altered alpha-2 adrenoceptor sensitivity.
Clonidine challenge testing assesses adrenoceptor function.
Imipramine is a common antidepressant treatment for panic disorder.

Purpose of the Study:

To investigate the effects of imipramine treatment on clonidine-induced responses in panic disorder patients.
To assess changes in biochemical, physiological, hormonal, and psychological parameters before and after imipramine therapy.

Main Methods:

Six patients with panic disorder underwent clonidine challenge testing.
Tests were performed before and after a course of imipramine treatment.
Measurements included plasma MHPG, blood pressure, heart rate, growth hormone, and sedation levels.

Main Results:

Imipramine treatment significantly reduced the clonidine-induced fall in plasma MHPG.
Smaller decreases in diastolic blood pressure and heart rate were observed post-treatment.
Growth hormone and sedation responses to clonidine remained unaltered by imipramine.

Conclusions:

Imipramine treatment appears to reduce the sensitivity of central alpha-2 adrenoceptors in panic disorder patients.
These adrenoceptor changes may partially contribute to the therapeutic efficacy of imipramine.
The observed alterations do not fully account for the antidepressant mechanisms in panic disorder.