Further evidence for a relationship between changes in GABA concentration in rat brain and enhanced monoamine-mediated behavioural responses following repeated electroconvulsive shock

Anxiety in major depression and cerebrospinal fluid free gamma-aminobutyric acid

BACKGROUND

Low gamma-aminobutyric acid (GABA) is implicated in both anxiety and depression pathophysiology. They are often comorbid, but most clinical studies have not examined these relationships separately. We investigated the relationship of cerebrospinal fluid (CSF) free GABA to the anxiety and depression components of a major depressive episode (MDE) and to monoamine systems.

METHODS AND MATERIALS

Patients with a DSM-IV major depressive episode (N = 167: 130 major depressive disorder; 37 bipolar disorder) and healthy volunteers (N = 38) had CSF free GABA measured by gas chromatography mass spectroscopy. Monoamine metabolites were assayed by high performance liquid chromatography. Symptomatology was assessed by Hamilton depression rating scale.

RESULTS

Psychic anxiety severity increased with age and correlated with lower CSF free GABA, controlling for age. CSF free GABA declined with age but was not related to depression severity. Other monoamine metabolites correlated positively with CSF GABA but not with psychic anxiety or depression severity. CSF free GABA was lower in MDD compared with bipolar disorder and healthy volunteers. GABA levels did not differ based on a suicide attempt history in mood disorders. Recent exposure to benzodiazepines, but not alcohol or past alcoholism, was associated with a statistical trend for more severe anxiety and lower CSF GABA.

CONCLUSIONS

Lower CSF GABA may explain increasing severity of psychic anxiety in major depression with increasing age. This relationship is not seen with monoamine metabolites, suggesting treatments targeting the GABAergic system should be evaluated in treatment-resistant anxious major depression and in older patients.

Seizure expression during electroconvulsive therapy: relationships with clinical outcome and cognitive side effects

Since electroconvulsive therapy (ECT) can result in generalized seizures that lack efficacy, physiological markers of treatment adequacy are needed. Specific electroencephalographic (EEG) features differentiate seizures produced with barely suprathreshold right unilateral (RUL) ECT, an ineffective treatment, from effective forms of ECT. This study determined whether EEG features are sensitive to treatment condition using a broad dosing range for RUL ECT, as well as predictive of clinical and cognitive outcomes. Quantitative EEG measures and observer ratings were compared in predictive power. From a larger study, 54 in-patients with major depression were randomized to low (1.5 x seizure threshold (ST)), moderate (2.5 x ST), or high-dose (6 x ST) RUL ECT, or high-dose (2.5 x ST) bilateral (BL) ECT. High dosage RUL and BL ECT were comparable in efficacy, and superior to low and moderate dosage RUL ECT. In the slow frequency bands (delta), BL ECT resulted in greater ictal power, ictal coherence, and postictal suppression than each RUL ECT condition, but the EEG measures failed to discriminate the RUL ECT groups. EEG measures were modestly associated with clinical outcome, with greater ictal power, delta coherence, and postictal suppression positive predictors. None of the EEG measures were associated with cognitive outcomes. Inability to distinguish forms of RUL ECT differing markedly in dosage and efficacy suggests that EEG measures have limited potential as markers of treatment adequacy. Rather than assaying treatment adequacy, the EEG features associated with efficacy may reflect individual differences in the strength of inhibitory processes that terminate the seizure, and can help isolate the biological variability that predisposes to positive or negative clinical response to ECT.

Repeated electroconvulsive stimuli: changes in neuropeptide Y, neurotensin and tachykinin concentrations in time

1. The effects of repeated electroconvulsive stimuli (ECS) on neuropeptide Y (NPY)-, neurokinin A (NKA)-, substance P (SP)- and neurotensin (NT)- like immunoreactivity (-LI) levels in specific rat brain regions were studied in order to establish changes in peptide tissue concentrations in time after the last ECS. 2. The rats were sacrificed 15 minutes, 60 minutes, 1 day, 7 days or 15 days after the sixth sham ECS or ECS, using focused microwave irradiation. 3. Following dissection of the brains, peptides were extracted and measured in extract aliquots by radioimmunoassays. 4. ECS increased NPY-LI in both right and left hippocampus, frontal cortex and occipital cortex at 15 min, 60 min and 1 day after the treatments. Seven days following the last treatment, NPY-LI concentrations were elevated in the left hippocampus and occipital cortex but not in the corresponding right structures. Fifteen days following the last ECS treatment no changes in NPY concentrations were seen. 5. Also NKA-LI was increased in both the right and left hippocampus; the duration of changes was identical to those of NPY-LI. 6. No effects on SP- or NT-LI were found. 7. These results are in line with our hypothesis that one of the ECT's mechanisms of action might involve its effects on NPY and NKA.

Electroconvulsive therapy in Parkinson's disease and other movement disorders

Early case reports note marked improvements in the signs of Parkinson's disease (PD) in several patients with coexisting psychiatric disorders after treatment with electroconvulsive therapy (ECT). Studies since 1959 reveal improvement of parkinsonism in over half of PD patients receiving ECT, regardless of the presence or absence of psychiatric comorbidity. Drug-induced parkinsonism, tardive dystonia, and tardive dyskinesia have also been shown to improve with ECT administration; tic syndromes have achieved mixed results. In animals, ECT enhances dopamine-mediated effects and increases GABA concentrations in the CNS. Optimal parameters relevant to the antiparkinsonism effects of ECT require further study.

Repeated ECS enhances dopamine D-1 but not D-2 agonist-induced behavioural responses in rats

The present study examined the effect of acute and repeated administration of electroconvulsive shock (ECS) on behaviours induced by various dopamine agonists in rats. Components of behavioural arousal induced by the dopamine D-1 agonist SKF 38393, the dopamine D-2 agonist RU 24213 and the mixed D-1/D-2 agonist apomorphine were assessed using a behavioural check-list method. Also, the overall behavioural syndrome produced by these drugs was measured using rating scales. Rats receiving repeated (5 times over 10 days) but not a single ECS showed enhanced grooming and sniffing in response to SKF 38393 (7.5 mg/kg) when compared to controls. Repetitive sniffing induced by apomorphine (0.5 mg/kg) was also enhanced by repeated ECS. Neither repeated nor a single ECS significantly changed behaviours induced by RU 24213 (0.75 mg/kg), although a downward trend was evident. The behaviour rating scale measurements also demonstrated that repeated administration to ECS increased behavioural responsiveness to SKF 38393 and apomorphine but not RU 24213. These results suggest that the increase of dopamine-mediated behaviour in rats seen after chronic ECS relates to an increase in central dopamine D-1 receptor function.

Chronic electroconvulsive shock and neurotransmitter receptors--an update

Electroconvulsive shock (ECS) produces many neurochemical alterations which may be related to its efficacy in the treatment of different psychiatric disorders. This review focuses particularly on experimental findings of CNS receptor changes in animals following chronic ECS and relates them to neurotransmitter and behavioral changes. Also, the pharmacological effect of other antidepressant treatment are compared. Possible mechanisms of action are discussed.

Electroconvulsive shock and L-dopa reduce head-turning induced by electrical stimulation of the caudate nucleus in the rat

The effect of repeated electroconvulsive shock (ECS) and L-dopa on contralateral head-turning induced by electrical stimulation of the caudate nucleus in rats was determined. Repeated ECS treatment consisting of a single daily ECS for 10 days was found to increase the number of caudate stimuli required to induce head-turning. As reported by others, oral L-dopa (250 mg/kg) was also found to antagonize the caudate stimulation-induced head-turning. The repeated ECS treatment had an additive effect with the 250 mg/kg L-dopa dose to increase the number of stimulations to induce the head-turn. These findings support previous reports that repeated ECS enhances dopamine-mediated behaviors as well as the theory that caudate stimulation-induced head-turning is mediated in part by dopaminergic mechanisms.

Neurochemical aspects of depression: the past and the future?

The role of aberrant neurochemical substrates in the etiology of depression and the neurochemical mechanisms of antidepressant therapies have been the subjects of many hypotheses in the last 30 years. Pharmacological studies of early antidepressant drugs indicated that brain monoamines were significantly affected by these drugs and these led to the formulation of the biogenic amine hypothesis of depression. Although this hypothesis has been of heuristic value in the study of drug mechanisms and has provided a basis for screening drugs for antidepressant potential, deficiencies in it have become apparent. Neuroanatomical and neurochemical considerations favour the view that brain noradrenaline and serotonin systems may serve as bias adjusting systems for each other and numerous other neural systems. As a consequence of such a relationship, a primary defect in some other neural system would appear amplified in measurements of serotonin or noradrenaline. A possible site for this primary defect may be in membrane composition and function. Recent studies have found that typical and other antidepressant therapies have a pronounced effect on membrane lipids. Thus, in view of the important functions of membrane lipids and the fact that they have been linked to the initiation and development of a number of other disease processes, it is now suggested that consideration be given to them as playing primary causal roles in the etiology of depression and as a site of action for antidepressant drugs.

Some anticonvulsant drugs alter monoamine-mediated behaviour in mice in ways similar to electroconvulsive shock; implications for antidepressant therapy

The effects in mice of administration of the anticonvulsants, progabide, sodium valproate, diazepam, carbamazepine and phenytoin on 5-hydroxytryptophan (5-HTP)-induced head-twitch, apomorphine-induced locomotion, clonidine-induced sedation, and beta-adrenoceptor and 5-HT2 receptor number have been examined. Repeated progabide administration (400 mg kg-1, i.p. twice daily for 14 days) enhanced the head-twitch response the effect lasting for over 8 days after the last dose, and also increased 5-HT2 receptor number in frontal cortex. Progabide (400 mg kg-1, i.p.) enhanced the head-twitch response when given once daily for 10 days and when given intermittently (5 times over 10 days) but not after 1 day of administration. Repeated Na valproate (400 mg kg-1, i.p.) also increased the 5-HTP-induced head-twitch response and 5-HT2 receptor number in the frontal cortex when given twice daily for 14 days, but no behavioural enhancement was seen after 10 days' treatment. Diazepam (1.25 mg kg-1, i.p.) twice daily for 14 days increased the head-twitch response and 5-HT2 receptor number. Repeated progabide and valproate (but not diazepam) administration attenuated the sedation response to the alpha 2-adrenoceptor agonist, clonidine (0.15 mg kg-1) but neither drug altered beta-adrenoceptor number in the cerebral cortex. No changes in apomorphine-induced locomotor behaviour were seen after progabide, valproate or diazepam. Repeated carbamazepine (20 mg kg-1) or phenytoin (40 mg kg-1) administration failed to alter any of the biochemical or behavioural parameters listed above. Like repeated electroconvulsive shock (ECS), progabide altered the head-twitch response, clonidine-induced sedation response and 5-HT2 receptor number. Unlike repeated ECS, it did not alter beta-adrenoceptor number or the apomorphine-induced locomotor response. These data suggest that ECS may produce some changes in monoamine function by altering GABA metabolism as has previously been postulated.

Diazepam administration to mice prevents some of the changes in monoamine-mediated behaviour produced by repeated electroconvulsive shock treatment

Administration to mice of electroconvulsive shock (ECS) five times over 10 days results in an enhanced 5-HTP-induced head twitch response, an enhanced apomorphine-induced locomotor response and an attenuated sedation response to the alpha 2-adrenoceptor agonist clonidine. Diazepam (1.25 mg/kg IP) injected 5 min before each ECS abolished the enhanced 5-HT- and dopamine-mediated responses but left the attenuated sedation response unaltered. When diazepam was given 5 min after each convulsion it still had the same effect, although its effects on the ECS-induced changes was blocked by administration of the specific benzodiazepine antagonist Ro 15-1788 (10 mg/kg IP) at the same time as diazepam. It is concluded that diazepam can abolish the ECS-induced changes in 5-HT- and DA-mediated behaviour, but not alpha 2-adrenoceptor-mediated responses, possibly by interfering with post-ictal changes. The implications for administration of benzodiazepines during electroconvulsive therapy (ECT) are discussed.

Chronic antidepressants and GABA "B" receptors: a GABA hypothesis of antidepressant drug action

Amitryptyline (10 mg/kg), desipramine (5 mg/kg), citalopram (10 mg/kg) and viloxazine (10 mg/kg) were administered to rats either acutely (decapitation 1 hr after i.p. injection) or subacutely (by subcutaneous minipump implantation for 18 days followed by decapitation 24 hr after removal). After acute administration there was not any consistent alteration in GABA levels, GAD activity, 3H GABA "A" or 3H-GABA "B" receptor binding or 3H-nipecotic acid binding to the recognition site for GABA uptake in the frontal cortex or hippocampus. Upon subacute antidepressant drug infusion, GABA levels, GAD activity and 3H-GABA-"A" binding showed only scattered differences in drug treated animals as compared to saline treated rats. However, 3H-GABA "B" binding in the frontal cortex was consistently elevated after all drug treatments (in % of control: amitryptyline = 155%; desipramine = 151%; citalopram = 173%; viloxazine = 189%). Scatchard analysis showed that this was due to a Bmax increase without an effect in Kd. These findings were reproduced by subacute administration of pargyline, a MAO inhibitor. These data suggest that GABA "B" receptors may be involved in the mechanism of action of antidepressant drugs and provide a link between GABAergic and monoaminergic hypotheses of depression.

Repeated electroconvulsive shock has no specific anxiolytic effect but reduces social interaction and exploration in rats

Administration of repeated electroconvulsive shock (ECS) to rats did not result in a specific anxiolytic profile in the social interaction test, but did significantly reduce several spontaneous behaviours: social interaction, locomotor activity, exploratory head-dipping and rearing. None of these behavioural changes was reversed by the administration of pentylenetetrazol prior to each seizure, a treatment that abolishes ECS-induced changes in GABA and 5-HT in the brain.

Antidepressant treatments: effects in rodents on dose-response curves of 5-hydroxytryptamine- and dopamine-mediated behaviours and 5-HT2 receptor number in frontal cortex

The effects of repeated electroconvulsive shock (ECS) administration, repeated desmethylimipramine injection (5 mg kg-1, twice daily for 14 days) and acute administration of the beta-adrenoceptor, clenbuterol, on 5-hydroxytryptamine (5-HT)- and dopamine-mediated behaviours in mice have been examined. All three treatments enhanced the carbidopa/5-hydroxytryptophan (5-HTP)-induced head-twitch response at all doses of 5-HTP examined, producing a parallel shift in the dose-response curve. A single ECS administration or single dose of desmethylimipramine had no effect. Only repeated ECS enhanced the locomotor response to injection of apomorphine. The dose-response curve shift was not parallel. A single ECS had no effect. A 6-hydroxydopamine lesion of brain dopamine terminals also enhanced the apomorphine response, but again did not produce a parallel shift in the dose-response curve. Both repeated ECS and repeated desmethylimipramine administration to rats increased the number of 5-HT2 receptor sites in rat brain. Clenbuterol had no effect. The enhancing effects of repeated ECS and clenbuterol administration on the 5-HTP-induced head-twitch response were additive. Enhanced 5-HT-mediated behavioural responses are seen in both mice and rats after these treatments. If it is assumed, therefore, that similar receptor changes occur in both species it appears that there is no relationship in either behavioural system between the ability of the treatment to alter receptor number and the change in the dose-response curve (parallel or non-parallel). All three antidepressant treatments (ECS, a tricyclic and a beta-adrenoceptor agonist) increase 5-HT-mediated behavioural responses although clenbuterol did not increase 5-HT2 receptor number. Only ECS increased dopamine-mediated responses.

Increased 5-HT2 receptor number in brain as a probable explanation for the enhanced 5-hydroxytryptamine-mediated behaviour following repeated electroconvulsive shock administration to rats

Following electroconvulsive shock (ECS) administration daily for 10 days there was an increase (35%) in 5-hydroxytryptamine2 (5-HT2) receptor number in rat frontal cortex 24 h after the last ECS, compared with handled controls. A similar increase was seen after intermittent ECS administration (5 ECS over 10 days) given during halothane anaesthesia, compared with halothane-treated controls. The dissociation constant was also increased at this time. A single ECS had no effect. Treatment of rats with pentylenetetrazol, p-chlorophenylalanine or alpha-methyl p-tyrosine during the intermittent ECS administration abolished the increase in 5-HT2 receptor binding. Since enhanced 5-HT-mediated behavioural responses are seen after repeated ECS but not when the ECS is given with the drug treatments outlined above, it is suggested that ECS-induced enhancement of 5-HT-mediated behaviour results from an increase in 5-HT2 receptor number.

Regional GABA concentration and [3H]-diazepam binding in rat brain following repeated electroconvulsive shock

It has been confirmed that 24 hours following a series of electroconvulsive shocks (ECS) given once daily for 10 days (ECS X 10) to rats there is an increase in GABA concentration in the corpus striatum. A similar change was seen after the ECS had been given to rats anaesthetised with halothane, or when 5 ECS were given spread out over 10 days, the rats being anaesthetised during the ECS. A daily convulsion for 10 days elicited by flurothyl exposure resulted in an increased striatal GABA concentration, but also increased the GABA concentration in the hypothalamus, hippocampus and cortex. The increase in striatal GABA concentration was present 24 hours after ECS daily for 5 days or 3 days after ECS daily for 10 days. No change in [3H]-diazepam binding was seen in hippocampus, cortex or corpus striatum 24 hours after the last of 10 once daily ECS. The increase in striatal GABA concentration was therefore seen at all times when enhanced monoamine-mediated behaviours have been demonstrated following seizures.