The dopamine β-hydroxylase inhibitor, nepicastat, suppresses chocolate self-administration and reinstatement of chocolate seeking in rats

Acute inhibition of dopamine β-hydroxylase attenuates behavioral responses to pups in adult virgin California mice (Peromyscus californicus)

In biparental species, in which both parents care for their offspring, the neural and endocrine mediators of paternal behavior appear to overlap substantially with those underlying maternal behavior. Little is known, however, about the roles of classical neurotransmitters, such as norepinephrine (NE), in paternal care and whether they resemble those in maternal care. We tested the hypothesis that NE facilitates the initiation of nurturant behavior toward pups in virgin male and female California mice (Peromyscus californicus), a biparental rodent. Virtually all parents in this species are attracted to familiar and unfamiliar pups, while virgins either attack, avoid, or nurture pups, suggesting that the neurochemical control of pup-related behavior changes as mice transition into parenthood. We injected virgin males and females with nepicastat, a selective dopamine β-hydroxylase inhibitor that blocks NE synthesis (75 mg/kg, i.p.), or vehicle 2 h before exposing them to a novel pup, estrous female (males only), or pup-sized novel object for 60 min. Nepicastat significantly reduced the number of males and females that approached the pup and that displayed parental behavior. In contrast, nepicastat did not alter virgins' interactions with an estrous female or a novel object, suggesting that nepicastat-induced inhibition of interactions with pups was not mediated by changes in generalized neophobia, arousal, or activity. Nepicastat also significantly reduced NE levels in the amygdala and prefrontal cortex and increased the ratio of dopamine to NE in the hypothalamus. Our results suggest that NE may facilitate the initiation of parental behavior in male and female California mice.

A Phaseolus vulgaris Extract Reduces Cue-Induced Reinstatement of Chocolate Seeking in Rats

Previous evidence has suggested that treatment with a standardized dry extract of Phaseolus vulgaris reduced intake and operant self-administration of highly palatable foods and fluids in rats and mice. The present study was designed to assess whether such extract was also effective in reducing seeking behavior for a highly hedonic chocolate-flavored beverage, using a "reinstatement" procedure adopted from the drug addiction research field and modeling relapse behavior. Rats were initially trained to lever-respond for the chocolate-flavored beverage under the Fixed Ratio (FR) 10 schedule of reinforcement. Subsequently, rats were exposed to an extinction responding phase, during which lever-responding - being unreinforced - diminished progressively up to extinction. Lever-responding was then powerfully reinstated by the non-contingent presentation of a complex of gustatory, olfactory, auditory, and visual stimuli previously associated to the availability of the chocolate-flavored beverage. Acute, intragastric administration of P. vulgaris dry extract (100 and 500 mg/kg) reduced lever-responding by 40-45%, in comparison to vehicle condition. These results indicate the ability of P. vulgaris dry extract to reduce seeking behavior for a highly palatable nourishment in an experimental model of relapse into disordered eating of palatable foods. The unavailability of the chocolate-flavored beverage in the reinstatement session tends to exclude that the observed effect of the P. vulgaris dry extract was secondary to any inhibition of carbohydrate metabolism; conversely, it is the likely consequence on a central action on the rewarding and hedonic properties of food.

Selective inhibition of dopamine-beta-hydroxylase enhances dopamine release from noradrenergic terminals in the medial prefrontal cortex

INTRODUCTION

Disulfiram has been claimed to be useful in cocaine addiction therapy, its efficacy being attributed to dopamine-beta-hydroxylase (DBH) inhibition. Our previous results indicate that disulfiram and the selective DBH inhibitor nepicastat increase extracellular dopamine (DA) in the rat medial prefrontal cortex (mPFC), and markedly potentiated cocaine-induced increase. Concomitantly, in rats with cocaine self-administration history, cocaine-seeking behavior induced by drug priming was prevented, probably through overstimulation of D1 receptors due to the DA increase. The present research was aimed at studying the neurochemical mechanisms originating the enhanced DA release.

METHODS

Noradrenergic system ablation was attained by intracerebroventricular (i.c.v.) administration of the neurotoxin anti-DBH-saporin (aDBH-sap). DA, noradrenaline (NA), and DOPAC were assessed by HPLC after ex vivo tissue extraction or in vivo microdialysis. Control and denervated rats were subjected to microdialysis in the mPFC and caudate nucleus to evaluate the effect of nepicastat-cocaine combination on extracellular DA levels and their regulation by α2-adrenoceptors.

RESULTS

Fifteen days after neurotoxin or its vehicle administration, tissue and extracellular NA were reduced to less than 2% the control value, while extracellular DA was increased by approximately 100%. In control rats, nepicastat given alone and in combination with cocaine increased extracellular DA by about 250% and 1100%, respectively. In denervated rats, nepicastat slightly affected extracellular DA, while in combination with cocaine increased extracellular DA by 250%. No differences were found in the caudate nucleus. Clonidine almost totally reversed the extracellular DA elevation produced by nepicastat-cocaine combination, while it was ineffective in denervated rats.

CONCLUSIONS

This research shows that the increase of extracellular DA produced by nepicastat alone or in combination with cocaine was prevented by noradrenergic denervation. The results indicate that nepicastat enhances DA release from noradrenergic terminals supposedly by removing NA from α2-autoreceptors. In addition to the inhibition of DA uptake, the latter mechanism may explain the synergistic effect of cocaine on nepicastat-induced DA release.

The dopamine β-hydroxylase inhibitor, nepicastat, reduces different alcohol-related behaviors in rats

BACKGROUND

Recent experimental data indicate that treatment with the selective dopamine β-hydroxylase inhibitor, nepicastat, suppressed different reward-related behaviors, including self-administration of chocolate and reinstatement of cocaine and chocolate seeking, in rats. This study was designed to extend to different alcohol-related behaviors the investigation on the "anti-addictive" properties of nepicastat.

METHODS

Sardinian alcohol-preferring (sP) rats, selectively bred for excessive alcohol consumption, were exposed to different procedures of alcohol drinking and self-administration.

RESULTS

Repeated treatment with nepicastat (0, 25, 50, and 100 mg/kg, intraperitoneally [i.p.], once daily for 10 consecutive days) produced a stable and dose-related reduction in daily alcohol intake in sP rats exposed to the homecage 2-bottle "alcohol (10% v/v) versus water" choice regimen with unlimited access. Acute treatment with nepicastat (0, 25, 50, and 100 mg/kg, i.p.) completely suppressed the "alcohol deprivation effect" (i.e., the temporary increase in alcohol intake occurring after a period of abstinence; model of alcohol relapse episodes) in sP rats exposed to the 2-bottle choice regimen. Acute treatment with nepicastat (0, 25, 50, and 100 mg/kg, i.p.) dose dependently and selectively reduced oral alcohol self-administration in sP rats trained to lever respond for alcohol (15% v/v) on a fixed ratio 4 schedule of reinforcement. Finally, combination of nepicastat (0, 50, and 100 mg/kg, i.p.) and alcohol (2 g/kg, intragastrically) did not alter spontaneous locomotor activity in sP rats.

CONCLUSIONS

Together, these data extend to alcohol the capacity of nepicastat to suppress different behaviors motivated by natural stimuli and drugs of abuse.

Disulfiram for binge eating disorder: an open trail

OBJECTIVE

To evaluate the efficacy and safety of disulfiram for treatment of binge eating disorder.

METHOD

Two hundred and fifty milligrams per day of disulfiram was administered to 12 patients affected by binge eating disorder for 16 weeks; the number of binge eating episodes per week and the number of participants who reported side effects were evaluated.

RESULTS

Nine participants (75.0%) completed the trial, while the other 3 (25.0%) discontinued prematurely. Disulfiram significantly decreased the mean frequency of binge eating episodes per week from 7.9±1.2 to 0.9±0.6 (p<.001). All patients (100.0%) reduced the frequency of binge eating episodes, and 7 participants (58.3%) achieved remission of binge eating. Eleven participants (91.7%) reported side effects [drowsiness (N=9), headache (N=7), dysgeusia (N=3), tachycardia (N=3), dizziness (N=2), and nausea (N=2)].

DISCUSSION

While disulfiram reduced the frequency of binge eating episodes, side effects were observed in the majority of participants. Longer-term placebo-controlled studies are warranted to exclude the contribution of a placebo response from these results and to evaluate drugs with similar pharmacological activity but improved tolerability.