Large amounts of an odorant-binding protein have been isolated from submaxillary glands of mature male pig. This polypeptide molecule is sex-specific, being absent in females. On electrophoretic gels under denaturing conditions it migrated as a broad band with an apparent molecular mass of around 20 kDa. Electrospray mass spectrometry revealed the presence of three main components, whose mass differences are not interpretable as result of any common post-translational modifications, indicating the presence of distinct polypeptide chains. N-terminal Edman degradation yielded a single sequence of 29 amino acids. It includes the lipocalin signature (-G-X-W-) and shows clear homology with a subclass of odorant-binding proteins present in mouse saliva, nasal mucus and urine. The purified protein still retained small ligands tightly bound ; among them 5A-androst-16-en-3-one and 5A-androst-16-en-3A-ol, both known sex pheromones for the pig, were identified. The protein also binds 2-isobutyl-3-methoxypyrazine, a good ligand for most odorant-binding proteins, with a dissociation constant of 5 µM.

These data demonstrate the capability of GS39,783 to attenuate the reinforcing properties of alcohol in alcohol-preferring rats. These data constitute a further piece of experimental evidence in support of the hypothesized role for the GABA(B) receptor in the control of alcohol drinking and reinforcement.

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Pharmacological blockade of the cannabinoid CB1 receptor has been repeatedly reported to suppress intake of food, including highly palatable foods, in laboratory animals. This study was designed to investigate whether treatment with the cannabinoid CB1 receptor antagonist, rimonabant, would reduce the reinforcing and motivational properties of a chocolate-flavoured beverage [containing 5% (w/v) chocolate powder] in nonfood-deprived and nonwater-deprived Wistar rats trained to self-administer this beverage under an operant conditioning procedure. This study was also aimed at assessing to what degree self-administration behaviour could be manipulated environmentally. After a period of training and maintenance of the self-administration behaviour, separate groups of rats were exposed to different experimental conditions [session length varying from 20 to 120 min; fixed ratio (FR) schedule of reinforcement varying from FR10 to FR40; reinforcer presentation varying from 2.5 to 10 s; concentration of the chocolate powder varying from 5% (w/v) to 0%]; other rat groups were used to test the effect of acute and repeated treatment with rimonabant (1-5.6 mg/kg, intraperitoneally) on two schedules of reinforcement (FR10 and progressive ratio) and extinction responding. All rats rapidly acquired and steadily maintained high levels of self-administration of the chocolate-flavoured beverage. Changes in experimental conditions modified the rats' self-administration behaviour; these changes seemed to be the result of the rats' attempt to adjust their behaviour so as to consume as much of the chocolate-flavoured beverage as possible when it was presented at its most palatable 5% concentration. Treatment with rimonabant dose-dependently suppressed self-administration of the chocolate-flavoured beverage. When rimonabant was administered repeatedly, only a modest degree of tolerance developed to its reducing effect. Finally, treatment with rimonabant resulted in a dose-dependent reduction of the motivational properties of the chocolate-flavoured beverage, measured by the progressive ratio schedule of reinforcement and extinction-responding procedure. These results suggest that self-administration of a chocolate-flavoured beverage can be rapidly and reliably established in rats and that this behaviour is environmentally manipulable. These results also suggest that the cannabinoid CB1 receptor is a crucial component of the neural substrate mediating the reinforcing and motivational properties of a highly palatable food such as a chocolate-flavoured beverage.