Aromatase and 5-alpha reductase gene expression: modulation by pain and morphine treatment in male rats.

Background: The steroid hormone testosterone has been found to be greatly reduced by opioids in different experimental and clinical conditions. The purpose of this study on male rats was to determine the effects of a single injection of morphine (5 mg/Kg) on persistent pain (formalin test) and the single or combined effects on p450-aromatase and 5-alpha reductase type 1 mRNA expression in the brain, liver and testis. Testosterone was determined in the plasma and in the brain, morphine was assayed in the plasma.

Sex differences in the analgesic effects of ICI 182,780 and Flutamide on ureteral calculosis in rats.

To better define the involvement of gonadal hormones in the sex differences observed in experimental visceral pain, we administered antagonists of estrogen receptors (ICI 182,780 [ICI]) or androgen receptors (Flutamide [FLU]) to adult male and female rats suffering from artificial ureteral calculosis. Subjects were divided into groups and treated with one of the substances (ICI, FLU) or sweet almond oil (OIL, vehicle) for 5 days, starting 2 days before surgery. On day 3, animals underwent surgery, with half receiving an artificial calculosis (Stone) and half only a sham procedure.

Modifications in DARPP-32 phosphorylation pattern after repeated palatable food consumption undergo rapid habituation in the nucleus accumbens shell of non-food-deprived rats.

In non-food-deprived rats a palatable meal induces a transient increase in dopamine output in the prefrontal cortex and nucleus accumbens shell and core; habituation to this response develops with a second palatable meal, selectively in the shell, unless animals are food-deprived. A palatable meal also induces time-dependent modifications in the dopamine and cAMP-regulated phosphoprotein of Mr 32 000 (DARPP-32) phosphorylation pattern that are prevented when SCH 23390, a selective dopamine D(1) receptor antagonist, is administered shortly after the meal. This study investigated whether dopaminergic habituation in the shell had a counterpart in DARPP-32 phosphorylation changes.

Hypothalamus-pituitary-adrenal modifications consequent to chronic stress exposure in an experimental model of depression in rats.

Unlabelled: The modifications in the hypothalamus-pituitary-adrenal (HPA) axis function induced by repeated unavoidable stress exposure, according to a standardized procedure used for inducing an experimental model of depression, were studied. Rats exposed to this procedure show hyporeactivity to both pleasurable and aversive stimuli and this condition is antagonized by the repeated administration of classical antidepressant drugs. We also studied whether imipramine administration during stress exposure would interfere with the possible modifications in the HPA axis.