The effect of single and repeated electroconvulsive shock (ECS) on locomotor activity in rats

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.

The effect of electroconvulsive shock seizures on behaviour induced by dopaminergic agonists and on immobility in the Porsolt test

Male, Wistar rats were given a course of eight electroconvulsive shock seizures (ECS group) or matched handling (control group). They were then tested for locomotion and rearing (7 days post-ECS), for grooming and yawning (9 days post-ECS), and for immobility in the Porsolt test (7, 14 and 21 days post-ECS). Seven days post-seizure, the ECS group showed significantly more locomotion following intraperitoneal administration of apomorphine (0.2 mg/kg), but not following injections of amphetamine (1 mg/kg). Drug-induced rearing was not different in the ECS and control animals. Nine days post-seizure, the ECS group showed significantly more grooming induced by the D-1 dopamine receptor agonist, SKF 38393 (1 mg/kg), but no difference in the yawning induced by the D-2 dopamine receptor agonist, quinpirole (0.05 mg/kg). In the Porsolt test, immobility was decreased in the ECS animals at 7 and 14, but not at 21 days post-ECS. It is concluded that ECS increases activity in the dopaminergic systems of the rat brain for at least 1-2 weeks post-seizure. The beneficial effects of electroconvulsive therapy (ECT) may relate to these dopaminergic alterations.

Locomotor suppressive and anxiolytic-like effects of urocortin 3, a highly selective type 2 corticotropin-releasing factor agonist

Murine urocortin 3 (mUcn 3), a member of the corticotropin releasing factor (CRF) peptide family, was recently identified. Of known agonists, this neuropeptide displays the highest degree of selectivity in binding to the CRF(2) receptor. These experiments sought to test the hypothesis that CRF(2) receptors have a role in modulating stress by examining intracerebroventricular (i.c.v.) administration of mUcn 3 in animal models of activation and anxiety. To investigate the effects of mUcn 3 on motor activity, rats were injected with mUcn 3 (0, 0.1, 1.0 or 10 microg, i.c.v.) 10 min prior to testing and activity was monitored for 6 h. To determine changes in novelty-induced exploration, rats were injected with mUcn 3 (0, 0.1, 1.0 or 10 microg, i.c.v.) 10 min prior to testing and examined in the elevated plus maze. Finally, delayed effects of mUcn 3 were tested in rats injected with 1.0 microg of mUcn 3 or vehicle 30 or 60 min prior to testing in the elevated plus maze. Injections of mUcn 3 significantly decreased locomotor activity in rats during the first hour of testing. In the elevated plus maze, mUcn 3 injections significantly increased open arm preference compared to vehicle when tested using a 10-min pretreatment interval. mUcn treated rats tested in the elevated plus maze following the delayed pretreatment interval did not differ from controls. These data demonstrate that injection of mUcn 3 leads to acute locomotor suppressive effects and decreases in stress-like behaviors, indicating an anxiolytic-like action for mUcn 3, and suggests a possible role of the CRF(2) receptor in the regulation of stress-related behavior.

Transcranial magnetic stimulation in an amphetamine hyperactivity model of mania

OBJECTIVES

Transcranial magnetic stimulation (TMS) of the brain has been reported to have therapeutic effects in mania, as well as depression. TMS has previously been reported to have effects similar to those of electroconvulsive shock in rat models of depression.

METHODS

We, therefore, studied TMS in amphetamine-induced hyperactivity as a rat model of mania.

RESULTS

While two and seven daily TMS sessions significantly reduced activity after amphetamine, twice-daily TMS for 7 days enhanced activity after amphetamine.

CONCLUSIONS

The results suggest that TMS treatment to rats interacts with the effects of amphetamine; the specific effects may be dependent on the schedule of treatment.

Long-term changes in regional brain cytochrome oxidase activity induced by electroconvulsive treatment in rats

Quantitative cytochrome oxidase (CO) histochemistry was used to examine brain regional metabolic effects of electroconvulsive shock-induced seizures (ECS). Rats receive a course of either eight ECS or control treatments and were sacrificed either 24 h or 28 days after the last session. Regional CO activity (mumol/gT/min) was quantitated throughout the brain using internally calibrated standards. Twenty-four hours after the last ECS session there was no significant difference between ECS- and sham-treated brains in any of the 99 brain regions examined. In contrast, 28 days after the last session, ECS brains showed significant increases in CO activity in the interpeduncular nucleus (+20%), bed nucleus of the stria terminalis (+25%), dorsomedial hypothalamus (+20%), ventromedial hypothalamus (+12%), mammillary nucleus (+14%), pontine nucleus (+16%), basolateral amygdala (+14%), medial amygdala (+12%), piriform cortex (+12%) and ventromedial thalamus (+9%). These results suggest that ECS induces localized increases in brain CO activity which are long-lasting and may develop independently of additional stimulation. The fact that CO changes were predominantly in limbic areas suggests that they may be relevant to the antidepressant effects of ECS.

Locomotor behavior following kindling in three different brain sites

Spontaneous and drug-induced interictal and post-ictal locomotor behavior of rats was investigated following electrical 'kindling' of different limbic structures at 3 brain sites which differ in the relative amount of innervation from dopamine cells of the ventral tegmentum: nucleus accumbens (N.Acc.), amygdala (AMYG), and dorsal hippocampus (DHPC). Kindling produced decreases in spontaneous post-ictal locomotion that did not appear to depend on the site of stimulation, but produced region specific attenuations in spontaneous interictal behavior as well as amphetamine-induced interictal and post-ictal responses. The most dramatic decreases were seen in N.Acc. kindled animals and the least dramatic were seen in rats kindled via DHPC. These data suggest that the mesolimbic dopamine system may participate in the changes in locomotion seen following kindled seizures, and may also provide a model for the study of human post-ictal and interictal behavior.