Behavioral and biochemical effects of repeated immobilization stress were determined in male Wistar rats. The influence of acute or repeated administration of antidepressant drugs on these effects of stress were also evaluated. It was found that repeated stress (immobilization 3 h/2 degrees C/4 days or various stressors/8 days) reduced basal locomotor activity of rats and prolonged immobility time in Porsolt's despair test. Antidepressant drugs (desmethylimipramine, imipramine, amitriptyline, clomipramine, mianserine), given acutely, restored basal locomotor activity of stressed rats to control level. Desmethylimipramine, imipramine and amitriptyline reduced immobility time in Porsolt's test similarly in control as in stressed rats. However clomipramine, mianserine and trazodone were effective in this test only in stressed rats. Imipramine given for 4 or 8 days (1 h before the stressor) normalized basal locomotor activity. Repeated (for 8 days) various stressors decelerated utilization of noradrenaline (NA) and dopamine (DA) in the brain. Imipramine given once a day for 8 days (1 h before the stressor) normalized brain utilization of catecholamines (CA). It was proposed that depression of basal motility and reduction of CA utilization in the brain induced by repeated stress may be counter acted by antidepressant drugs.

Animals↗

PubMedDate not supplied

Effects of electroconvulsive shock on central GABA-ergic mechanisms.

A single electroconvulsive shock (ECS) has no influence on seizures induced by picrotoxin and bicuculline, although it decreases the level of GABA in the cortex. A repeated ECS (once daily for 7 days) does not change the level of GABA in the cortex, brain stem, and cerebellum, but depresses seizures induced by both compounds. It prolongs the time of their occurrence and decreases their intensity. This effect is stronger in the case of bicuculline. It manifests itself in the increase of the number of animals protected from seizures and decrease of their lethality. Baclofen does not change ECS action on seizures induced by picrotoxin and bicuculline whereas it enhances catalepsy caused by ECS. Bicuculline does not change the time-course of catalepsy. The obtained results suggest that repeated ECS reduces the seizures induced by GABA antagonists probably y increasing GABA-ergic transmission or/and by increasing dopaminergic and serotoninergic transmission which significantly modify the activity of GABA-ergic neurons.

Animals↗

PubMedDate not supplied

Immobilization stress modifies locomotor response to catecholamine receptor agonists in rats.

The effects of dopaminergic (apomorphine, nomifensine, B-HT 920) and noradrenergic (methoxamine, clonidine, salbutamol) agonists on locomotor activity were investigated in rats submitted to acute (3 h) or repeated (3 h/4 days) immobilization stress. The stress-induced functional changes were monitored by the blood level of corticosterone and the number of lymphocytes as well as the brain utilization of NA and DA. The rats subjected to acute immobilization stress displayed 30 min later an enhanced locomotor activation after apomorphine, nomifensine, or methoxamine and reduced sedative effect of clonidine, salbutamol or B-HT 920. 24 h after the repeated stress only the locomotor responses to apomorphine, nomifensine, B-HT 920 and salbutamol were modified. Spontaneous locomotor activity was not significantly changed under the influence of stressful stimuli. Increased plasma corticosterone level, strong reduction of blood lymphocytes and enhanced NA and DA utilization in the brain of rats after acute stress, together with above mentioned results, suggest that short-lasting stress evokes (30 min later) significant functional changes not only in the blood but also in the brain: enhanced CA neurons activity as well as the increased alpha 1-adrenergic and DA-post-synaptic receptors responsiveness in parallel with reduced alpha 2 - and beta-adrenergic and DA-presynaptic receptors reactivity. On the other hand, 24 h after last session of repeated stress CA brain neurons activity was not changed, however DA and beta-adrenergic responsivity was farther modified. It is postulated that the stress conditions produce in NA and/or DA brain systems a state of readiness to locomotion activating stimuli.

Albuterol↗

PubMedDate not supplied

Interaction between antidepressants and alpha-adrenergic receptor blocking agents.

Yohimbine and phentolamine administered in doses regarded as blocking presynaptic alpha-adrenoreceptors counteracted locomotor sedation elicited in rats by antidepressant drugs (imipramine, nortriptyline and amitriptyline). The reduction of noradrenaline (NA) utilization in the brain evoked by a single dose of antidepressants and the increase of NA utilization induced by chronic treatment with imipramine or nortriptyline were prevented by yohimbine. The results indicate the role of presynaptic alpha-adrenoceptors in the influence of tricyclic antidepressants on NA neurons in the brain.

Adrenergic alpha-Antagonists↗

PubMedDate not supplied

The influence of insulin hypoglycemia on central dopaminergic structures of the rat.

Daily administration of insulin, 2 U/kg/day for 9 days, leads to a marked increase in the activity of central dopaminergic structures, reflected by an increase in the apomorphine or amphetamine-induced stereotypy and a decrease in fluphenazine-induced catalepsy. These changes are accompanied by a depression of cerebral dopamine and noradrenaline levels and a depression of noradrenaline utilization in the brain.

Amphetamine↗