Further observations on the effect of repeated electroconvulsive shock on the behavioural responses of rats produced by increases in the functional activity of brain 5-hydroxytryptamine and dopamine

Systemic Lupus Erythematous Presenting as Catatonia and its Response to Electroconvulie Therapy

Neuropsychiatric systemic lupus erythematous (SLE) encompasses various psychiatric and neurological manifestations that develop in SLE patients, secondary to involvement of central nervous system. Neuropsychiatric SLE, presenting as catatonia is very uncommon, and treatment of this condition is not well defined. Previously the role of benzodiazepines, immunosuppression, plasma exchange, and electroconvulsive therapy (ECT) has been described in its management. Here we describe a case of neuropsychiatric lupus presenting as catatonia that did not respond to benzodiazepines or immunosuppression. The symptoms of catatonia showed improvement with ECT. Furthermore, we have discussed the pathology of the disorder and the role of ECT in the treatment of cases of catatonia associated with SLE, who do not respond to benzodiazepines.

Electroconvulsive therapy alters dopamine signaling in the striatum of non-human primates

Electroconvulsive therapy (ECT) is one of the most effective therapies for depression and has beneficial motor effects in parkinsonian patients. However, little is known about the mechanisms of therapeutic action of ECT for either condition. The aim of this work was to explore the impact of ECT on dopaminergic function in the striatum of non-human primates. Rhesus monkeys underwent a course of six ECT treatments under a human clinical protocol. Longitudinal effects on the dopaminergic nigrostriatal system were studied over 6 weeks using the in vivo capabilities of positron emission tomography (PET). PET scans were performed prior to the onset of ECT treatments and at 24-48 h, 8-10 days, and 6 weeks after the final ECT treatment. Early increases in dopamine transporter and vesicular monoamine transporter 2 binding returned to baseline levels by 6 weeks post-ECT. Transient increases in D1 receptor binding were also observed, whereas the binding potential to D2 receptors was unaltered. The increase in dopaminergic neurotransmission suggested by our results may account in part for the therapeutic effect of ECT in mood disorders and Parkinson's disease.

Dopamine, schizophrenia, mania, and depression: Toward a unified hypothesis of cortico-striatopallido-thalamic function

Considerable evidence from preclinical and clinical investigations implicates disturbances of brain dopamine (DA) function in the pathophysiology of several psychiatric and neurologic disorders. We describe a neural model that may help organize theseindependent experimental observations. Cortical regions classically associated with the limbic system interact with infracortical structures, including the nucleus accumbens, ventral pallidum, and dorsomedial nucleus of the thalamus. In our model, overactivity in forebrain DA systems results in the loss of lateral inhibitory interactions in the nucleus accumbens, causing disinhibition of pallidothalamic efferents; this in turn causes rapid changes and a loss of focused corticothalamic activity in cortical regions controlling cognitive and emotional processes. These effects might be manifested clinically by some symptoms of psychoses. Underactivity of forebrain DA results in excess lateral inhibition in the nucleus accumbens, causing tonic inhibition of pallidothalamic efferents; this perpetuates tonic corticothalamic activity and prevents the initiation of new activity in other critical cortical regions. These effects might be manifested clinically by some symptoms of depression. This model parallels existing explanations for the etiology of several movement disorders, and may lead to testable inferences regarding the neural substrates of specific psychopathologies.

High but not low ECS stimulus intensity augments apomorphine-stimulated dopamine postsynaptic receptor functioning in rats

BACKGROUND

Clinical research shows that the antidepressant and cognitive adverse effects of electroconvulsive therapy are both dependent on the administered electrical stimulus intensity (dose); however, dose-dependent neurotransmitter system changes in the brain, which might underlie the therapeutic or adverse effects, remain to be demonstrated.

OBJECTIVE

We used a behavioral model to examine dose-related effects of electroconvulsive shock (ECS) on dopamine postsynaptic receptor functioning in the rat brain.

METHODS

In a factorially designed study, rats (n = 100) were treated with five once-daily ECSs at three levels (sham ECS, 30 mC ECS, and 120 mC ECS), and with drug at two levels (saline, and 1 mg/kg s.c. apomorphine). Motility was assessed in the small open field.

RESULTS

Apomorphine-elicited, dopamine postsynaptic receptor-mediated hypermotility was significantly increased by 120 mC ECS but not by 30 mC ECS. An additional but unrelated finding was that, while the ECS seizure duration expectedly decreased across time, no dose-dependent effects were observed.

CONCLUSION

ECS-induced dopamine postsynaptic receptor up-regulation may depend on the intensity of the administered electrical stimulus.

Repeated administration of fluoxetine, desipramine and tranylcypromine increases dopamine D2-like but not D1-like receptor function in the rat

We tested the effect of repeated treatment (twice daily for 14 days) of rats with the antidepressant drugs fluoxetine, desipramine and tranylcypromine, on the behavioural response to the non-selective dopamine (DA) receptor agonist, apomorphine, the D1-like receptor agonists, SKF 38393 and SKF 81297 and the D2-like receptor agonists, RU 24213 and quinpirole. Agonist-induced behaviour was monitored by automated activity meters and direct observation using a checklist scoring method. Fluoxetine, desipramine and tranylcypromine enhanced (albeit to a varying degree) the behavioural responses to apomorphine (0.75 mg/kg, s.c.), quinpirole (0.25 mg/kg, s.c.) and RU 24213 (0.75 mg/kg, s.c.). In contrast, fluoxetine, desipramine and tranylcypromine did not increase the behavioural responses to SKF 38393 (7.5 mg/kg, s.c.) and SKF 81297 (0.5 mg/kg, s.c.). Finally, fluoxetine, despiramine and tranylcypromine did not modify the behavioural responses to the concomitant administration of SKF 38393 (7.5 mg/kg, s.c.) and quinpirole (0.25 mg/kg, s.c.). Our data suggest that repeated administration of fluoxetine, desipramine and tranylcypromine increases central DA D2-like but not D1-like receptor function.

Neuropeptide Y in brains of the Flinders Sensitive Line rat, a model of depression. Effects of electroconvulsive stimuli and d-amphetamine on peptide concentrations and locomotion

Neuropeptide Y (NPY), has been implicated in the pathophysiology of depression and the mechanisms of action of electroconvulsive treatment (ECT). In this series of experiments, we explored whether there are differences between Flinders Sensitive Line (FSL) rats, an animal model of depression, and controls, Flinders Resistant Line (FRL) in (1) baseline brain NPY-LI concentrations, (2) effects of ECS on locomotion and brain neuropeptides, (3) amphetamine effects on behavior, and (4) effects of ECS pretreatment on subsequent effects of amphetamine on behavior. Both strains were divided into two groups, receiving eight ECS or ShamECS. Twenty-four hours after the last session, animals were habituated in activity boxes for 45 min before given d-amphetamine (1.5 mg.kg(-1), subcutaneously) or vehicle. Locomotor activity was then recorded for an additional 45 min. Twenty-four hours later, rats were sacrificed by microwave irradiation, the brains dissected into frontal cortex, occipital cortex, hippocampus, hypothalamus and striatum, and the neuropeptides extracted and measured by radioimmunoassay. No differences between FSL and FRL rats in baseline locomotor activity were found. FSL compared to FRL animals showed a significantly larger locomotion increase following saline and a significantly smaller increase following amphetamine. ECS pretreatment significantly decreased the saline effects on locomotion in the FSL and the amphetamine effects in the FRL rats. 'Baseline' NPY-like immunoreactivity (LI) concentrations were lower in the hippocampus of the 'depressed' rats. ECS increased NPY-LI in frontal cortex, occipital cortex and hippocampus of both strains. The hippocampal NPY-LI increase was significantly larger in the FSL compared to FRL animals.

Decreased levels of preprotachykinin-A and tachykinin NK1 receptor mRNA in specific region of the rat striatum after electroconvulsive stimuli

The effects of electroconvulsive stimuli on the expression of mRNAs coding for preprotachykinin-A and the substance P-sensitive tachykinin NK1 receptor were examined in subregions of the rat striatum. In the electroconvulsive stimuli-treated animals, a 43% decrease in preprotachykinin-A mRNA was detected in the dorso-lateral caudate-putamen as compared to sham electroconvulsive stimuli treated animals. A 75% decrease in numerical density of tachykinin NK1 receptor mRNA positive neurons was found in the caudal part of the nucleus accumbens core. These findings provide new evidence for selective effects of electroconvulsive stimuli on specific populations of neurons in the rat striatum.

Electroconvulsive shock increases dopamine D1 and D2 receptor mRNA in the nucleus accumbens of the rat

The present study examined the effects of acute and repeated administration of electroconvulsive shock (ECS) on levels of D1 and D2 receptor mRNAs in the nucleus accumbens and striatum (caudate-putamen) of the rat. Quantitative in situ hybridisation with 35S-labelled oligonucleotide probes specific for D1 and D2 receptor mRNAs was utilised. Compared to controls, rats receiving a single ECS showed higher levels of both D1 and D2 receptor mRNAs in the nucleus accumbens 4 h, but not 24 h, after treatment. Similarly, rats receiving ECS repeatedly (five ECS in 10 days) also exhibited higher levels of D1 and D2 receptor mRNAs in the nucleus accumbens 4 h, but not 24 h, after the last treatment. The effects of single and repeated ECS treatment on dopamine receptor mRNA levels were localised to the caudal region of the nucleus accumbens. No statistically significant changes in mRNA levels were detected in the striatum of rats treated with either acute or repeated ECS. We discuss the possibility that increased expression of D1 and D2 receptors in the nucleus accumbens may be involved in the dopamine-enhancing properties of ECS detected in behavioural studies.

Limbic effects of repeated electroconvulsive stimulation on neuropeptide Y and somatostatin mRNA expression in the rat brain

The aim of this study was to determine the effect of repeated electroconvulsive stimulation (ECS) on the expression of neuropeptide Y (NPY) and somatostatin (SS) mRNA in the rat brain. For that purpose, quantitative in situ hybridization histochemistry and RNA blot analysis were used. In the hippocampal formation the prevalence of NPY mRNA positive neurons increased in the hilus of the dentate gyrus and the CA3 while a decrease was seen in layers II-III of the entorhinal cortex. In contrast, SS mRNA was increased in the granule cells of the dentate gyrus and in most neurons of the outer parts of the layer III in the entorhinal cortex with cell bodies of perforant pathway projections to the hippocampal CA1 region. Both NPY and SS mRNA expressing neurons were increased in numerical density in the prefrontal cortex with similar amounts of mRNA in individual NPY positive neurons after the stimulations while SS mRNA levels decreased in hybridization positive neurons. In the striatum the only observed significant effect was an increased prevalence of NPY mRNA positive neurons in the caudal nucleus accumbens. Our results provide an outline of a complex functional anatomy of ECS in the rat brain. This type of investigations contributes to map the neuronal systems involved in the action of ECT used in the treatment of affective and schizophrenic disorders.

D1 receptor binding in rat striatum: modification by various D1 and D2 antagonists, but not by sibutramine hydrochloride, antidepressants or treatments which enhance central dopaminergic function

[3H]SCH 23390 is a selective high affinity ligand for D1 receptors in vitro. Using this ligand persistent blockade of D1 receptors by SCH 23390 and cis-flupenthixol was shown to significantly increase the number of D1 receptor binding sites in rat striatum. In contrast, repeated administration of the D2-selective antagonist, clebopride, resulted in a small, but significant, reduction in number. No differences in binding affinity were observed and a single dose of these compounds was without effect. The D2-selective antagonist, haloperidol, the non-selective D1/D2 receptor antagonist, chlorpromazine, the dopamine reuptake inhibitors, bupropion, GBR 12909 and nomifensine, and the dopamine releasing agent, d-amphetamine, had no effect on D1 receptors. The antidepressant treatments, desipramine, zimeldine, amitriptyline, tranylcypromine, mianserin and ECS and the monoamine reuptake inhibitor, sibutramine, similarly did not alter striatal D1 sites. Thus, of the treatments investigated only chronic receptor blockade by high affinity antagonists altered D1 receptor binding in rat striatum.

Physical exercise as a novel antidepressant agent: possible role of serotonin receptor subtypes

Long-term exercise is associated with an antidepressant effect in patients with mild to moderate forms of nonbipolar depression and appears to be a promising new approach to its treatment. Adaptive changes in serotonin (5-HT) receptor functioning appears to play an important role in mediating the action of various antidepressant treatments. We investigated the adaptive changes in behavioral sensitivity of the 5-HT receptor subtype following 4 weeks of swimming exercise in normal rats, as well as in an animal model of depression (3 week, variety of chronic stressors). 5-HT1A autoreceptor sensitivity was assessed by hyperphagic response induced by 8-OH-DPAT (0.25 mg/kg, IP); 5-HT1A postsynaptic receptor by 5-HT syndrome induced by 8-OH-DPAT (0.75 mg/kg, IP), and 5 Me-ODMT (5 mg/kg, IP); and 5-HT2 receptor by wet dog shakes response induced by quipazine (1 mg/kg, IP) and 5MeODMT (5 mg/kg, IP). It was observed that exercise training in normal rats resulted in enhanced sensitivity of the 5-HT2 receptors along with subsensitivity of 5-HT1A autoreceptors. Exercise, given prophylactically along with chronic stressors, was able to prevent the development of behavioral deficit in the open-field test, and the animals developed remarkably enhanced sensitivity of 5-HT2 receptors. This adaptive supersensitivity of 5-HT2 receptor is also seen after various antidepressant treatments and may play an important role in mediating the antidepressant action of exercise.

Differential involvement of voltage-dependent calcium channels in apomorphine-induced hypermotility and stereotypy

The involvement of the voltage-dependent calcium channel in behavioral effects of apomorphine was tested in naive rats and in animals which were morphine-abstinent or were subjected to chronic electroconvulsive treatment (ECS). In naive rats a calcium channel blocker, nifedipine, which by itself does not affect locomotor activity, inhibited the locomotor stimulation induced by apomorphine, while it facilitated stereotyped behavior. Morphine-abstinent and ECS-treated rats displayed elevated responsiveness to apomorphine, reflected by hypermotility and stereotyped behavior after a dose of 1 mg/kg IP that does not produce overt behavioral effects in naive animals. Nifedipine, 5 mg/kg IP, significantly reduced hypermotility produced by apomorphine in morphine abstinent or ECS-treated rats. The calcium channel blocker did not, however, antagonize enhanced stereotyped behavior. The results indicate that apomorphine hypermotility is controlled by dihydropyridine calcium channels and that enhancement of calcium channel density produced by morphine abstinence and by chronic ECS potentiates the hypermotility response. Calcium channels seem to be differently involved in control of apomorphine-induced hypermotility and stereotypy.

Role of the dopaminergic system in depression

A hypothesis implicating dopamine in depression was proposed over 15 years ago (Randrup et al 1975). The identification of multiple new subtypes of dopamine receptors and evolving views regarding the function of the dopamine systems in the brain require a reexamination of this hypothesis. Results from studies in depression, Parkinson's disease, and animal models of depression suggest a deficiency of dopamine in depression. Dopamine precursors, dopamine agonists, and dopamine reuptake inhibitors show therapeutic efficacy in depression. Electroconvulsive therapy (ECT) and standard pharmacological antidepressants enhance dopamine function. Studies using receptor-specific drugs in clinical trials and neuroimaging studies are needed to further clarify the role of dopamine in depression.

The effects of rubidium, caesium and quinine on 5-HT-mediated behaviour in rat and mouse--3. Quinine

It has been shown that caesium, which shares properties with quinine as a K(+)-channel blocker, enhanced 5-HT-mediated behaviour in both rats and mice. It was therefore of interest to investigate the effects of quinine on 5-HT-mediated behaviour in the rat and mouse. Quinine, dose-dependently (ED50 = 5 mg/kg), produced the 5-HT behavioural syndrome in rats pre-treated with tranylcypromine (TCP) (15 mg/kg, i.p.). p-Chlorophenylalanine (i.p., 300 mg/kg x2) or (-)-propranolol (20 mg/kg, i.p.), pindolol (4 mg/kg, i.p.) and ritanserin (0.4 mg/kg, s.c.), all prevented the behavioural syndrome induced by quinine (72 mg/kg, i.p.) plus TCP. The administration of quinine (72 mg/kg, i.p.) enhanced the 5-HT syndrome elicited by p-chloramphetamine (4 mg/kg, i.p.) and the 5-HT agonists, 8-OH-DPAT (0.5 mg/kg, s.c.), 5-MeODMT (2 mg/kg, i.p.), DOI (8 mg/kg, s.c.) and quipazine (25 mg/kg, i.p.) in rats. Pretreatment with quinine also potentiated the 5-HT2-mediated head-twitch in the mouse but had no effect on the hypothermia in the mouse, induced by 8-OH-DPAT (0.5 mg/kg, s.c.). Quinine also enhanced the rate of synthesis of 5-HT in the brain of the rat. On the basis of these findings, together with those in the preceding two papers, it is suggested that the effects of rubidium, caesium and quinine, to enhance differentially various aspects of 5-HT function are mediated by actions on 5-HT-modulated K(+)-channels. This conclusion is also discussed in relation to the actions of lithium and electroconvulsive shock on 5-HT function in brain and the treatment of manic-depressive disease.

MK-801 prevents the enhanced behavioural response to apomorphine elicited by repeated electroconvulsive treatment in mice

Repeated administration of electroconvulsive stimuli (ECS) to mice once daily for a period of 7 days results in an enhanced locomotor response induced by apomorphine (1.0 mg/kg, IP). Pretreatment (30 min) with the N-methyl-D-aspartate (NMDA) receptor antagonist, MK-801 (0.01-1.0 mg/kg IP), suppressed ECS-induced seizure activity in a dose-dependent manner. MK-801 (0.01 and 0.033 mg/kg, IP) given 30 min before each ECS dose-dependently decreased apomorphine-mediated responses. Administration of MK-801 (0.033 mg/kg IP) 30 min after each convulsion had the same effect. These results indicate that MK-801 can abolish the ECS-induced enhancement of dopamine-mediated behaviour possibly by interfering with postictal processes. Thus, NMDA receptors seem to be involved in the behavioural changes and presumably also in the neural adaptations produced by repeated ECS.

Augmentation of rat brain endogenous monoamine oxidase inhibitory activity (tribulin) by electroconvulsive shock

The effects of acute and subacute supramaximal and submaximal electroshock-induced convulsions on rat brain tribulin activity were investigated. Both supramaximal and submaximal shocks induced a marked increase, as measured 30 min after the onset of convulsions, with a significantly greater effect from the former. The effects were no longer present 24 h after stimulus. Repeated electroshock for 5 and 10 days showed that submaximal stimuli produced little change, whereas supramaximal shock brought about a significant increase in tribulin activity, the effect being greater with 10-day exposure. The results are not inconsistent with the clinical observation that a single electroconvulsive therapy (ECT) shock has little clinical usefulness but that repeated shocks, spread over several days, result in therapeutic benefit due, perhaps, to an increase in brain concentrations of tribulin, an endogenous monoamine oxidase inhibitor.

Effects of chronic electroconvulsive shock on interstitial concentrations of dopamine in the nucleus accumbens

There is accumulating evidence that chronic electroconvulsive shock (ECS) can increase the functional output of central dopaminergic systems. The present experiments investigated the effects of acute and chronic ECS on interstitial concentrations of dopamine (DA) in the nucleus accumbens (NAC) using in vivo microdialysis in awake freely moving rats. ECS (150 V, 0.75 s) increased interstitial concentrations of DA, DOPAC and HVA to approximately 130% of baseline values. The magnitude of the ECS-induced increase in DA was not affected by chronic ECS. In contrast, the response of the DA metabolites was attenuated in the chronic ECS group. Chronic ECS did not influence apomorphine (25 micrograms/kg, SC)-induced decreases in extracellular concentrations of DA or its metabolites in the NAC, thus providing no support for the hypothesis that chronic ECS produces subsensitivity of DA autoreceptors. d-Amphetamine (1.5 mg/kg SC)-induced increases in extracellular DA were significantly prolonged in the NAC of the chronic ECS group. In accordance with previous reports, the locomotor stimulant effects of d-amphetamine were also enhanced in the chronic ECS group. These data provide further evidence that chronic ECS can increase certain behavioral and neurochemical indices of meso-accumbens DA function.

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.

Localized alterations of dopamine receptor binding in rat brain by repeated electroconvulsive shock: an autoradiographic study

The effects of repeated electroconvulsive shock (ECS) on binding parameters of D1 and D2 type dopamine (DA) receptors were investigated in different brain regions of male rats using quantitative autoradiography. D1 binding was studied with [3H]SCH 23390 as the ligand and D2 binding with [3H]spiroperidol. The distribution patterns of both D1 and D2 receptor sites were in good agreement with previously published reports. Repeated ECS induced upregulation of D1 receptors in the olfactory tubercle, the endopiriform nucleus and the substantia nigra without appreciably affecting D1 binding sites in the striatum, n. accumbens or in other brain regions containing D1 binding sites. Upregulation of D2 binding sites, after ECS, was seen in the accumbens, the olfactory tubercle, the amygdaloid nuclei, the claustrum and the endopiriform nucleus, but not in the caudate-putamen or in other brain regions containing D2 binding sites. The present finding that repeated ECS can selectively upregulate DA receptor binding sites in discrete brain areas, including limbic structures, renders important support to a large number of previous studies that demonstrated effects of repeated ECS on DA receptor function in behavioral models.

Electrotherapy in mice: dopaminergic and noradrenergic effects in the Tail Suspension Test

The Tail Suspension Test (TST) is a psychotropic screening test which is used principally to detect antidepressant activity. Electrotherapy (ECT) is used to treat depressions which are resistant to the usual antidepressant drugs and has proved to have a profile in the TST approaching that of antidepressants after treating mice at the rate of 2 shocks per day for 5 days. The results of a single treatment were not statistically different from those of the control group, whereas single daily treatment for 5 days showed a reduction in immobility which did not differ significantly from the control group. The reduction in immobility, induced by 5 days of ECT treatment twice daily, was antagonized by sulpiride and prazosin but not by yohimbine, methysergide, metergoline and DL propranolol. The results suggest that electrotherapy leads to an increase in noradrenergic and dopaminergic activities expressed by a reduction in immobility in the TST.

Depression and antidepressant therapy: receptor dynamics

1. The classical norepinephrine (NE) and serotonin (5-HT) theories of depression have been abandoned in light of recent chronic antidepressant drug studies. 2. The new NE and 5-HT theories of depression focus on the dynamics of receptor subtypes in depression and chronic antidepressant treatments. 3. Recent studies in molecular genetics suggest a reclassification of monoamine receptors based on receptor structural homologies in DNA and amino acid sequences rather than receptor affinity for ligands. 4. Electrophysiologic studies in rats suggest that 5-HT1 receptor function is facilitated by chronic antidepressant treatment. 5. Preclinical studies employing a range of 5-HT1 mediated behavioral models also suggest that chronic antidepressant treatment facilitates transmission at central 5-HT1 receptors. 6. Patient studies, employing a 5-HT1 mediated neuroendocrine model, suggest that depression is associated with decreased transmission at CNS 5-HT1 receptors; and that chronic antidepressant treatment facilitates 5-HT1 receptor responsiveness in depressed patients. 7. New 5-HT1 selective agonists have been developed and found to be clinically effective antidepressants. 8. The above clinical and preclinical data suggest that some forms of depression are related to a decreased responsiveness of 5-HT1 receptors which is reversed by chronic antidepressant treatment. 9. Beta adrenergic and NE-stimulated cyclic AMP studies suggest that chronic antidepressant treatment decreases the responsiveness of central beta-adrenergic receptors, particularly beta-1 receptors. 10. A novel approach to antidepressant drug development focuses on identifying centrally active beta-1 agonists, which like clinically proven antidepressants, decrease beta-1 receptor responsiveness with chronic treatment. 11. 5-HT2 receptor binding studies and initial studies of 5-HT2 receptor coupled PI turnover suggest that chronic antidepressant treatment decreases 5-HT2 receptor number and function. 12. The development of new atypical antidepressants with 5-HT2 receptor related mechanisms of action suggest that 5-HT2 receptors may be associated with certain types of depression and their clinical treatment.

Repeated treatment with antidepressant drugs and/or electroconvulsive shock (ECS) does not affect the quinpirole-induced elevation of the serum corticosterone concentration in rats

The selective dopamine D2 receptor agonist quinpirole (0.03-1 mg/kg intra peritoneally) increased dose-dependently the serum corticosterone level in rats. The effect of the maximum dose of quinpirole (0.3 mg/kg intraperitoneally) was antagonized in a dose- dependent manner by the selective D2 receptor antagonist sulpiride (3-30 mg/kg intra peritoneally), but not by the selective D(1) receptor antagonist SCH-23390 (3 mg/kg intra peritoneally). Imipramine and amitriptyline (10 mg/kg per os), administered acutely or repeatedly (twice daily for 14 days), did not affect the corticosterone response to quinpirole (0.1 mg/kg intraperitoneally). The response was modified neither in animals treated repeatedly with electroconvulsive shock (ECS) (seven shocks every 2 days), nor after their combined repeated treatment with imipramine and ECS. The above results indicate that repeated treatment with antidepressant drugs and/or ECS does not affect the sensitivity of dopamine D2 receptors involved in the corticosterone response to quinpirole.

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.

Electroconvulsive treatment attenuates behavioral response to SKF 38393 in reserpine-treated mice

Electroconvulsive treatment (ECT) of mice, once daily for 7 days, significantly reduced the stimulation of motor activity induced by the selective dopamine (DA) D1-receptor agonist SKF 38393 (15 mg/kg IP), but significantly increased the motor stimulation by the unselective DA-receptor agonist apomorphine (1.5 mg/kg IP) in reserpine-treated (10 mg/kg IP) mice, when compared to control mice, receiving sham ECT. The results provide a functional correlate to previously observed ECT-induced down-regulation of D1 receptor sites in DA-rich regions of the rodent brain. Such an effect may be significant for clinical actions of ECT in affective disorders and, possibly, in Parkinson's disease.

Effects of chronic electroconvulsive shock on D1 and D2 dopamine receptor-mediated activity of adenylate cyclase in homogenates of striatum and limbic forebrain of rat

Stimulation of adenylate cyclase by dopamine in homogenates of the striatum was unaltered in rats which had received either a single or a series of 10 electroconvulsive shock, compared to those which received sham treatment. In homogenates of the limbic forebrain, stimulation by both 100 microM dopamine and by 4 microM SKF 38393 was significantly increased after chronic electroconvulsive shock. The activity of D2 receptors, as measured by inhibition of forskolin-stimulated adenylate cyclase, in the presence of the D1 receptor antagonist SCH 23390, was unaltered by chronic electroconvulsive shock in either area of the brain. The selective effect of chronic electroconvulsive shock in increasing the activity of D1 receptors may account both for the increase, in dopamine-mediated behaviour, seen after chronic electroconvulsive shock and for the antiparkinsonian effects of this treatment.

Modulation of second messenger function in rat brain by in vivo alteration of receptor sensitivity: relevance to the mechanism of action of electroconvulsive therapy and antidepressants

1. The second messengers cyclic AMP and inositol triphosphate are the intracellular mediators for a number of neurotransmitters for which receptors exist on brain neurons. 2. Up- or down-regulation of these receptors in general produce corresponding changes in the associated second messenger systems. 3. Chronic administration of antidepressants including electroconvulsive shock to rats produces a number of changes in cerebral receptors, notably down-regulation of beta-adrenergic and serotonin 5-HT2 receptors and up-regulation of alpha-1 adrenergic receptors. 4. The changes in receptor number induced by such antidepressant treatments are in general accompanied by corresponding changes in the associated second messenger reactions. 5. Antidepressant administration has also been shown to induce increased post-receptor mediated adenylate cyclase activity in cortical membranes, and similar effects have also been reported in striatum after chronic administration of neuroleptics. The relevance of these effects to the mechanism of action of the drugs is discussed.

Chronic antidepressant treatment increases the apomorphine-induced elevation of plasma corticosterone in rats

Plasma corticosterone concentrations in response to subcutaneous administration of apomorphine (25 and 200 micrograms kg-1) have been assessed in rats treated acutely (2 days) or repeatedly (15 days) with saline, clomipramine, electroshock and clomipramine + electroshock. Chronic, but not acute, antidepressant treatment decreased the corticosterone level which remained unchanged in control and in rats acutely treated with apomorphine. Chronic antidepressant treatment significantly increased the corticosterone response to apomorphine. Neuroendocrine evidence is provided for an increased responsiveness of dopamine receptors which are thought to mediate the apomorphine effect on corticosterone secretion following chronic antidepressant treatment.

Hypothermia induced by baclofen, a possible index of GABAB receptor function in mice, is enhanced by antidepressant drugs and ECS

1 Intraperitoneal injection to mice of the gamma-aminobutyric acidB (GABAB) receptor agonist (+/-)-baclofen induces a dose-dependent decrease in rectal temperature. 2 Injection of (-)-baclofen intracerebroventricularly at doses that had no effect when given peripherally induced a marked hypothermia. (+)-Baclofen was without effect. 3 The decrease in rectal temperature induced by (-)-baclofen when injected intraperitoneally was highly correlated with an increase in sedation. 4 Repeated administration of amitriptyline (10 mg kg-1 daily for 14 days) resulted in mice displaying an enhanced temperature and sedation response to injection of (+/-)-baclofen (5 mg kg-1) 24 h after the last dose of antidepressant. 5 An enhanced hypothermic response was also seen following repeated administration of zimeldine, mianserin or desipramine (all 10 mg kg-1 daily for 14 days) or repeated electroconvulsive shock (ECS; 5 ECS over 10 days) 24 h after the last treatment. 6 A single administration of any of the antidepressant drugs or ECS or repeated administration of the anxiolytic drug flurazepam (20 mg kg-1 daily for 14 days) did not alter the baclofen-induced hypothermic response. 7 Administration of (+/-)-baclofen (5 mg kg-1) daily for 5 or 14 days attenuated the baclofen-induced hypothermic response. However, one pretreatment dose did not alter the response. 8 It has previously been reported that repeated baclofen administration decreases GABAB receptor number in the brain while repeated administration of antidepressant drugs and ECS increases the density of this receptor. The current data therefore suggest that baclofen-induced hypothermia may provide a simple index of GABAB receptor function in the brain and strengthens the evidence that GABAB receptor function is enhanced by antidepressant drugs and ECS.

On the mechanism of potentiation of apomorphine-induced stereotypy due to electroconvulsive shock

Electroconvulsive shock-induced changes in the intensity of stereotype induced by apomorphine, the binding of [3H]spiroperidol in the corpus striatum, the accumulation of [3H]dopamine in brain and the permeability of the blood-brain barrier, were monitored in rats 30 min after single, or 24 hr after chronic (once daily for 7 days) electroconvulsive shock. There was significant potentiation in stereotypy induced by apomorphine after chronic electroconvulsive shock. The binding of [3H]spiroperidol did not show any change in the affinity (Kd) or density (Bmax) of receptors in the striatum after acute or chronic electroconvulsive shock. The accumulation of dopamine increased significantly in the hypothalamus after acute electroconvulsive shock and in the corpus striatum and hypothalamus after chronic electroconvulsive shock. A significant increase in the entry of sodium fluorescein into the hypothalamus occurred after acute electroconvulsive shock; it increased in all the regions of the brain after chronic electroconvulsive shock. Alteration in the blood-brain barrier (BBB) by electroconvulsive shock leading to increased accumulation of dopamine in the corpus striatum may be responsible for the potentiation of stereotypy.

Effects of single and repeated electroconvulsive shock on local cerebral glucose utilization in the conscious rat

Local rates of cerebral glucose utilization (LCGU) were determined in adult rats submitted to electroconvulsive shock (ECS) treatment. One group of rats (n = 5) received a single ECS, a second group (n = 5) was treated once daily for 7 days. A third group (n = 5) of unshocked rats served as control. LCGU measurements were performed one day after either the single or the last ECS. Following a single ECS, most of the 45 brain regions examined exhibited lower rates of LCGU than controls, in contrast after repeated ECS treatment the metabolic activity results increased in segments of the hippocampus. The results indicate that repeated ECS treatment selectively increases metabolic rates within the hippocampus, a structure of the limbic system thought to be related to affective disorders and memory.