Sex-dependent differences are frequently observed in the biological and behavioural effects of substances of abuse, including cannabis. We recently demonstrated a modulating effect of sex and oestrous cycle on cannabinoid-taking and seeking behaviours. Here, we investigated the influence of sex and oestrogen in the regulation of cannabinoid CB1 receptor density and function, measured by [³H]CP55940 and CP55940-stimulated [³⁵S]GTPγS binding autoradiography, respectively, in the prefrontal cortex (Cg1 and Cg3), caudate- putamen, nucleus accumbens, amygdala and hippocampus of male and cycling female rats, as well as ovariectomised (OVX) rats and OVX rats primed with oestradiol (10 µg/rat) (OVX+E). CB1 receptor density was significantly lower in the prefrontal cortex and amygdala of cycling females than in males and in OVX females, a difference that appeared to be oestradiol-dependent, because it was no more evident in the OVX+E group. CP55940-stimulated [³⁵S]GTPγS binding was significantly higher in the Cg3 of OVX rats relative to cycling and OVX+E rats. No difference was observed in CB1 receptor density or function in any of the other brain areas analysed. Finally, sex and oestradiol were also found to affect motor activity, social behaviour and sensorimotor gating in rats tested in locomotor activity boxes, social interaction and prepulse inhibition tasks, respectively. Our findings provide biochemical evidence for sex- and hormone- dependent differences in the density and function of CB1 receptors in selected brain regions, and in behaviours associated with greater vulnerability to drug addiction, revealing a more vulnerable behavioural phenotype in female than in male rats.

We have analysed the long-term effects of adolescent (postnatal day 28–43) exposure of male and female rats to nicotine (NIC, 1.4 mg/kg/day) and/or the cannabinoid agonist CP 55,940 (CP, 0.4 mg/kg/day) on the following parameters measured in the adulthood: (1) the memory ability evaluated in the object location task (OL) and in the novel object test (NOT); (2) the anxiety-like behaviour in the elevated plus maze; and (3) nicotinic and CB₁ cannabinoid receptors in cingulated cortex and hippocampus. In the OL, all pharmacological treatments induced significant decreases in the DI of females, whereas no significant effects were found among males. In the NOT, NIC-treated females showed a significantly reduced DI, whereas the effect of the cannabinoid agonist (a decrease in the DI) was only significant in males. The anxiety-related behaviour was not changed by any drug. Both, nicotine and cannabinoid treatments induced a long-lasting increase in CB₁ receptor activity (CP-stimulated GTPγS binding) in male rats, and the nicotine treatment also induced a decrease in nicotinic receptor density in the prefrontal cortex of females. The results show gender-dependent harmful effects of both drugs and long-lasting changes in CB₁ and nicotinic receptors.

Ventral tegmental area dopamine neurons control reward-driven learning, and their dysregulation can lead to psychiatric disorders. Tonic and phasic activity of these dopaminergic neurons depends on cholinergic tone and activation of nicotinic acetylcholine receptors (nAChRs), particularly those containing the β2 subunit (β2*-nAChRs). Nuclear peroxisome proliferator-activated receptors type-α (PPARα) tonically regulate β2*-nAChRs and thereby control dopamine neuron firing activity. However, it is unknown how and when PPARα endogenous ligands are synthesized by dopamine cells. Usingex vivoandin vivoelectrophysiological techniques combined with biochemical and behavioral analysis, we show that activation of α7-nAChRs increases in the rat VTA both the tyrosine phosphorylation of the β2 subunit of nAChRs and the levels of two PPARα endogenous ligands in a Ca²⁺-dependent manner. Accordingly,in vivoproduction of endogenous PPARα ligands, triggered by α7-nAChR activation, blocks in rats nicotine-induced increased firing activity of dopamine neurons and displays antidepressant-like properties. These data demonstrate that endogenous PPARα ligands are effectors of α7-nAChRs and that their neuromodulatory properties depend on phosphorylation of β2*-nAChRs on VTA dopamine cells. This reveals an autoinhibitory mechanism aimed at reducing dopamine cell overexcitation engaged during hypercholinergic drive. Our results unveil important physiological functions of nAChR/PPARα signaling in dopamine neurons and how behavioral output can change after modifications of this signaling pathway. Overall, the present study suggests PPARα as new therapeutic targets for disorders associated with unbalanced dopamine–acetylcholine systems.

Human rIL-1 alpha and -1 beta are shown to increase significantly the CFU-culture activity in the spleen as well as at other sites after i.v. or i.p. administration. IL-1 can also significantly increase survival and can "rescue" a number of animals if administered either before or after lethal doses of cyclophosphamide or gamma-irradiation. The protective and reconstitutive activities of the rIL-1 are shown to correlate with increased CFU-culture frequency and total number, as well as increased cellularity in the bone marrow and peripheral blood, suggesting that this is one of their mechanisms of action. The sequence and timing of administration of human rIL-1 is critical for the protection or rescue of animals receiving DNA-damaging agents; maximal activity is achieved when IL-1 is given 20 h before insult or 48 h after alkylating agent administration. Minimal therapeutic activity is observed with IL-1 as a single agent for the treatment of metastatic disease compared with other biologic response modifiers including IFN-gamma.