Pharmacological challenge with a serotonin 1D agonist in alcohol dependence

Serotonin function in pathological gambling: blunted growth hormone response to sumatriptan

Pathological gambling is a disruptive behaviour and an important public health concern that is classified as an impulse control disorder, and is also conceptualized as a prototype of 'behavioural addiction'. Its phenomenology cannot be reduced to a single neurobiological dysfunction; instead, it has been conceived as a complex chain of events in which the serotonergic system (5-HT) has often been suggested as one of the most prominent involved. Acute administration of Sumatriptan, a selective 5-HT(1B/1D) agonist, has been used to investigate the functional responsivity of 5-HT(1B/1D) receptors in alcoholics, resulting in a blunted growth hormone response. These findings have been interpreted as being due to the down-regulation of these receptors. However, previous studies could not rule out the possibility that the changes in receptor function were induced by chronic substance exposure. Twenty-two pathological gamblers and 19 healthy control subjects were evaluated in response to double-blind administration of both a single dose of oral Sumatriptan (100 mg) and of placebo in a crossover design. All participants were screened to ensure that they were negative for lifetime alcohol and drug addiction, and had been free of substance abuse for at least 6 months. Outcome measures included growth hormone, prolactin, gambling severity, mood, craving and 'high' change scales. A blunted growth hormone response was observed in pathological gamblers compared with healthy controls after Sumatriptan administration. No statistically significant differences were found for prolactin or behavioural measures, except for an increase in anxiety over time in pathological gamblers. These results, together with those obtained in our previous serotoninergic challenge study, document the presence of a serotonergic dysfunction in pathological gamblers similar to that reported in alcoholics.

Enhanced 5-HT(2A) receptor status in the hypothalamus and corpus striatum of ethanol-treated rats

AIM

Brain is the major target for the actions of ethanol and it can affect the brain in a variety of ways. In the present study we have investigated the changes in 5-HT level and the 5-HT(2A) receptors in the ethanol-treated rats.

METHODS

Wistar adult male rats of 180-200 g body weight were given free access to 15% (v/v) (approx.7.5 g/Kg body wt./day) ethanol for 15 days. Controls were given free access to water for 15 days. Brain 5-HT and its metabolites were assayed by high performance liquid chromatography (HPLC) integrated with an electrochemical detector (ECD) fitted with C-18-CLS-ODS reverse phase column. 5-HT(2A) receptor binding assay was done with different concentrations of [3H] MDL 100907.

RESULTS

The hypothalamic 5-HT content significantly increased (P < 0.001) with a decreased (P < 0.001) 5-HIAA/5-HT turnover in the ethanol-treated rats when compared to control. The corpus striatum 5-HT content significantly decreased (P < 0.01) with increased (P < 0.01) 5-HIAA/5- HT turnovers in the ethanol-treated rats when compared to control. Scatchard analysis of [(3)H] MDL 100907 against ketanserin in hypothalamus showed a significant increase (P < 0.001) in B(max )with a decreased affinity (P < 0.001) in ethanol-treated rats when compared to control. The competition curve for [3H] MDL 100907 against ketanserin fitted one-site model in all the groups with unity as Hill slope value. An increased K(i) and log (EC(50)) value were also observed in ethanol-treated rats when compared to control. Scatchard analysis of [3H] MDL 100907 against ketanserin in the corpus striatum of ethanol-treated rats showed a significant increase (P < 0.001) in B(max) and in affinity (P < 0.01) when compared to control. The change in affinity of the receptor protein in both corpus striatum and hypothalamus shows an altered receptor. The competition curve for [(3)H] MDL 100907 against ketanserin fitted one-site model in all the groups with unity as Hill slope value. There was no significant change in K(i) and log (EC (50)) value in ethanol-treated rats when compared to control.

CONCLUSION

The present study demonstrated the enhanced 5-HT(2A) receptor status in hypothalamus and corpus striatum. The ethanol-induced enhanced 5-HT(2A) receptors in the hypothalamus and corpus striatum has clinical significance in the better management of ethanol addiction. This will have therapeutic application.

Diplotypes of the human serotonin 1B receptor promoter predict growth hormone responses to sumatriptan in abstinent alcohol-dependent men

BACKGROUND

Some studies have associated alcohol dependence (AD) with the human serotonin (5-HT)(1B) receptor (HTR1B). This investigation explored the functional responsivity of HTR1B in abstinent AD men using a sumatriptan challenge, while measuring genetic heterogeneity in the HTR1B promoter.

METHODS

Abstinent AD men (n = 27) and abstinent men without any alcohol use disorder (n = 19) were administered 6 mg of sumatriptan succinate, subcutaneously. Plasma samples collected over the following 2 hours were assayed for growth hormone (GH) concentrations. His DNA was genotyped for the A-161T and T-261G polymorphisms of the HTR1B promoter and diplotypes determined.

RESULTS

Integrated GH responses were predicted by interactions of AD and promoter diplotypes, as well as subject ethnicity. The final model accounted for nearly 35% of the variance in GH responses. Post hoc evaluation revealed that AD was associated with a blunting of GH secretion only among individuals with the most common HTR1B diplotype (TT/TT).

CONCLUSIONS

A blunting of GH responses in abstinent AD men was observed only among those with the most common HTR1B promoter diplotype. Less common promoter diplotypes appeared protective. Controlling for genetic background is a useful augmentation of case-control pharmacological challenge strategies designed to elucidate the psychobiology of AD and other complex disorders.

Serotonin dysfunction in pathological gamblers: increased prolactin response to oral m-CPP versus placebo

OBJECTIVE

Acute administration of the partial serotonin (5-HT) agonist meta-chlorophenylpiperazine (m-CPP), that is used also as a street drug, has been reported to induce a "high" and craving response in various impulsive and substance addiction disorders.

INTRODUCTION

To clarify altered 5-HT metabolism in pathological gamblers and to explore the specific role of serotonergic system in non-substance addictions, we assessed behavioral ("high" and "craving") and neuroendocrine (prolactin and cortisol) responses to an oral single dose of m-CPP and placebo in pathological gamblers and matched controls. Moreover, the relationship between neuroendocrine outcome and clinical severity has been assessed.

METHOD

Twenty-six pathological gamblers and 26 healthy control subjects enter a double-blind, placebo-controlled-crossed administration of orally dose m-CPP 0.5 mg/kg. Outcome measures included prolactin and cortisol levels, gambling severity, mood, craving and "high" scales.

RESULTS

Pathological gamblers had significantly increased prolactin response compared to controls at 180 minutes and at 210 minutes post-administration. Greater pathological gamblers severity correlated with increased neuroendocrine responsiveness to m-CCP, suggesting greater 5-HT dysregulation. Pathological gambling patients had a significantly increased "high" sensation after m-CPP administration compared with control.

CONCLUSION

These results provide additional evidence for 5-HT disturbance in pathological gamblers and they support the hypotheses that the role of the 5-HT dysfunction related to the experience of "high" might represent the pathway that leads to dyscontrolled behavior in pathological gamblers. Furthermore, the "high" feeling induced by m-CPP in pathological subjects may represent a marker of vulnerability to both behavioral and substance addictions.