ABSTRACT
The avoidance responses of mice exposed to the hot plate (55 degrees C) were found to be modified when tested a second time. In fact, when forepaws licking was no longer observed, the rearing was clearly anticipated (7 s instead of 15 s) as well as jumping (24 s instead of 55 s). These modifications of avoidance strategies as well as their latencies were still observed even 24 days after the first exposure. Avoidance responses were prevented by morphine or haloperidol injected prior to the first exposure, but not with scopolamine or diazepam. These modifications were not affected in mice injected with morphine or submitted to either a supramaximal electroshock or to ether anesthesia delivered immediately after the first hot plate exposure. Among the various known types of memory, these modifications could be linked to procedural memory.
Subject(s)
Avoidance Learning/physiology , Dementia/prevention & control , Pain/physiopathology , Reaction Time/physiology , Thermosensing/physiology , Analysis of Variance , Animals , Anticonvulsants/administration & dosage , Avoidance Learning/drug effects , Behavior, Animal , Dementia/etiology , Diazepam/administration & dosage , Dopamine Antagonists/pharmacology , Dose-Response Relationship, Drug , Electroshock/adverse effects , Ether/therapeutic use , Haloperidol/pharmacology , Male , Mice , Morphine/pharmacology , Muscarinic Antagonists/administration & dosage , Narcotics/pharmacology , Pain/drug therapy , Pain/etiology , Pain Measurement/methods , Pain Threshold/drug effects , Pain Threshold/physiology , Reaction Time/drug effects , Scopolamine/administration & dosage , Thermosensing/drug effects , Time FactorsABSTRACT
Dopaminergic pathways play a key role in the central control of sexual behavior. Stimulation of central dopaminergic receptors elicits penile erection in a variety of species and has been proposed as a treatment option for erectile dysfunction in humans. The present study investigated the proerectile effects of apomorphine in mice. In this species, subcutaneous injection of apomorphine (range: 0.11-110 microg/kg sc) elicited three different behavioral responses: erection, erection-like responses and genital grooming. Proerectile effects of apomorphine were dose-dependent. More than 50% of mice displayed erections after administration of 1.1-11 microg/kg of apomorphine sc. Proerectile effects of apomorphine were blocked by haloperidol, a central D2 antagonist, but not by domperidone, a peripherally active dopaminergic antagonist. We conclude that apomorphine elicits erection in mice. This effect is dose-dependent and due to activation of central D2 dopaminergic receptors. The mouse model may be useful for pharmacological approaches designed to provide a better understanding of the central mechanisms of penile erection and sexual behavior.
Subject(s)
Apomorphine/pharmacology , Dopamine Agonists/pharmacology , Penile Erection/drug effects , Sexual Behavior, Animal/drug effects , Animals , Apomorphine/administration & dosage , Apomorphine/antagonists & inhibitors , Dopamine Agonists/administration & dosage , Dopamine Antagonists/pharmacology , Dose-Response Relationship, Drug , Haloperidol/pharmacology , Injections, Subcutaneous , Male , Mice , Mice, Inbred BALB C , Models, AnimalABSTRACT
Two lines of mice, previously selected for their sensitivity (BS) or their resistance (BR) to an anxiogenic benzodiazepine (BZ) receptor inverse agonist, methyl beta-carboline-3-carboxylate (beta-CCM), have recently been shown to present several differences in anxiety. In the present study, attempt was made to extend their behavioral profile in two situations classically used for testing antidepressant drugs. Reassessment of locomotor performance of these new populations confirmed that the motor activity of BR mice was lower than that of BS mice. In both the forced-swimming and the tail suspension tests, the immobility time of BS mice was significantly higher than that of BR mice. In the tail suspension test, two administrations of imipramine (30 mg/kg i.p., 5 h and 30 min before testing) significantly reduced the immobility time of BS mice but not of BR mice. From these data, it appears that BS mice are more "depressed" than BR mice. Thus, these selectively bred lines may represent potentially useful animal models to investigate behavioral, neurochemical and neuroendocrine correlates of antidepressant action.
