Anti-muricide mechanisms of chlorpromazine and imipramine in OB rats: Adrenoceptors and hypothalamic functions

The aggression theory of schizophrenia: revisited

The aggression theory of schizophrenia is a psychoanalytic theory which proposes that schizophrenia results from uncontrolled, deprivation-induced aggressive impulses. An animal model of the aggression theory is presented using predatory aggression as the source of arousal. Although neurochemical control of predatory aggression is nonspecific, anatomic control is located in the lateral hypothalamus across species. The lateral hypothalamus also controls schedule-induced polydipsia which has been implicated in schizophrenia. The aggression theory could be empirically evaluated by determining if schizophrenics respond differently than normals to scheduled feedings. Implications of the aggression theory are discussed.

Clozapine: strong antiaggressive effects with minimal motor impairment

Clinical studies have shown clozapine to be effective in the treatment of schizophrenia and associated with an extremely low incidence of extrapiramidal side effects. Diverse studies indicate that clozapine is an atypical neuroleptic with a preferential activity on the mesolimbic structures and a lower affinity for striatal D2 receptors than the classical antipsychotics. The purpose of this study was to assess the behavioral properties of clozapine, especially its effects on aggressive and motor behaviors. Individually housed male mice of the OF1 strain were exposed to anosmic "standard opponents" 30 minutes after the last drug administration. One category of animals received a single IP dose of the compound (0.2, 0.5, 1 or 1.5 mg/kg). Another category received daily doses (0.5, 1 or 1.5 mg/kg) for 21 days. Encounters were videotaped and behavior evaluated using an ethologically based analysis. Clozapine, in the acute treatment condition, produced a significant decrease in "attack" and "threat" behaviors without "immobility" being significantly increased. These results suggest a rather specific antiaggressive action of the compound with little motor impairment. In the chronic administration, no significant change in aggressive behavior was observed which may be attributed to the development of some degree of tolerance.

Brain output dysregulation induced by olfactory bulbectomy: an approximation in the rat of major depressive disorder in humans?

Mounting evidence indicates that the emotional, cognitive, neurovegetative and behavioral symptoms of patients with major depressive disorder are due to abnormal neurochemical substrates in the brain. Although the specific neurochemical abnormalities responsible have not been identified, the presenting symptoms of major depression are consistent with a disruption of normal neural communications between the limbic system and hypothalamus. Following removal of the olfactory bulbs, rats display a syndrome of behavioral deficits that also reflect a disruption of the limbic-hypothalamic axis. Moreover, the bulbectomy induced deficits are selectively reduced by the chronic administration of the same drugs that alleviate the symptoms of depression when given chronically to the patients. In addition to this pharmacological similarity, there are also numerous behavioral parallels between bulbectomized rats and major depression patients. The bulbectomized rat provides a good model in which to study antidepressant drugs and also may provide neurochemical and neuroanatomical data that are relevant to understanding the biological substrates of emotion and the causes of depression in humans.

Potentiation of haloperidol-induced catalepsy by beta-adrenoceptor antagonists in mice

Several clinical papers have reported that beta-adrenoceptor antagonists were useful in the management of schizophrenia and tardive dyskinesia. The present study examined effects of beta-antagonists on haloperidol (HAL)-induced catalepsy using mice in order to study the relationship between beta-antagonists and central dopaminergic functions. Catalepsy was tested by the standard bar test 30 min after intraperitoneal treatment of HAL. Beta-antagonists were administered subcutaneously just after HAL-treatment. Propranolol, alprenolol, oxprenolol and pindolol increased the incidence of catalepsy compared to HAL alone. Atenolol, not penetrating into the brain, and the sedative and hypnotic drug chlordiazepoxide did not potentiate it. These results suggest that the potentiation of HAL-catalepsy by beta-antagonists is based on their central action. Therefore, a central beta-receptor appears to be implicated in the regulation of the central dopaminergic functions.

Acute administration of MIF-1 or Tyr-MIF-1 inhibits haloperidol-induced catalepsy in rats

The effects of MIF-1 (Pro-Leu-Gly-NH2) and Tyr-MIF-1 (Tyr-Pro-Leu-Gly-NH2) on haloperidol-induced catalepsy were studied in order to examine the influences of both peptides on central dopaminergic function. In the first experiment, several variables were tested. It was found that the optimal effect was achieved with a dose of 1.0 mg/kg haloperidol injected SC an hour before testing for catalepsy and 1.0 mg/kg MIF-1 injected SC 30 min before testing. In the second experiment, Tyr-MIF-1 as well as MIF-1 were injected as single injections at four doses. Catalepsy was inhibited in an inverted U-shape dose-response relationship with the maximal effect of each peptide occurring at 1.0 mg/kg. The results indicate that when careful attention is given to dose, both MIF-1 and Tyr-MIF-1 can activate dopaminergic neuronal activity after acute administration.