Biomedical subjects

H G M Westenberg

Publications and source records attributed to H G M Westenberg.

3 recordsLinked to original sources

PubMed2004

Increasing dopaminergic activity: effects of L-dopa and bromocriptine on human sensory gating.

Schizophrenic patients show a loss of sensory gating, which is reflected in a reduced P50 suppression. Because most of the symptoms in schizophrenia can be reduced by antagonists of the dopaminergic (D2) system, the loss in sensory gating might be related to an increased dopaminergic activity. Therefore, in the present study, the effects of increased dopaminergic neurotransmisson on sensory gating in healthy volunteers were investigated. In a double-blind, balanced, placebo-controlled design, healthy male volunteers were challenged in two separate studies with either 300 mg L-dopa (precursor of dopamine) or placebo (n=16) and 1.25 mg bromocriptine (D2 agonist) or placebo (n=17). Subsequently, they were tested for their sensory gating (P50 suppression). P50 suppression values in the placebo condition were comparable to those found in literature. Although both L-dopa and bromocriptine reduced P50 amplitude, they did so in an equal ratio for both the response to the conditioning (C) and the testing (T) stimuli, therefore not resulting in a reduction of the P50 suppression ratio (T/C). In the present study, neither L-dopa nor bromocriptine reduced sensory gating in healthy volunteers. This suggests that an increased dopaminergic activity in humans is not responsible for the reduction in sensory gating as seen, for example, in schizophrenia.

Acoustic Stimulation↗

PubMed2002

Decrease in basal dopamine levels in the nucleus accumbens shell during daily drug-seeking behaviour in rats.

Accumbal dopamine (DA) is generally accepted to participate in the neural mechanisms underlying drug dependence. Recently the involvement of accumbal DA in drug-seeking behaviour has gained more experimental attention. To study an involvement of accumbal DA in drug-seeking behaviour within and between daily self-administration behaviour, changes in extracellular DA concentration in the nucleus accumbens (NAc) shell were measured during the daily dynamics of intravenous heroin and cocaine self-administration. Groups of drug naive rats were allowed to intravenously self-administer heroin (30 microg/infusion) and cocaine (30 microg/infusion) during five consecutive daily 3 h sessions. Extracellular DA concentrations in the NAc were measured before and after a single 3 h session (acute) and before and after 5 consecutive 3 h sessions (repeated). Following acute and repeated heroin and cocaine self-administration the extracellular DA concentration in the NAc shell was increased by two-fold to three-fold over baseline. These changes in DA concentrations are thought to reflect a direct effect of heroin and cocaine on DA neurotransmission in the NAC shell. Measurement of basal DA concentrations before the self-administration sessions revealed that just before the scheduled 5th self-administration session the (absolute) basal DA levels in the NAc in heroin or cocaine self-administering animals were decreased by approximately halve, as compared to drug-naive animals. It is assumed that just before a scheduled next session the (daily) desire for the drug is high. This decrease in basal DA neurotransmission in the NAc shell may, therefore, reflect an involvement of accumbal DA in drug-seeking behaviour during daily self-administration behaviour. The results demonstrate that initiation of i.v. heroin and cocaine self-administration is linked with changes in extracellular levels of DA in the NAc shell. Moreover, the present data suggest that accumbal DA might be involved in processes underlying the motivational aspects involved in daily drug-seeking behaviour, and that neuroadaptive changes in the mesolimbic DA system due to repeated drug intake lead to an tonic decrease in overall DA activity in the NAc.

Analgesics, Opioid↗

PubMed2002

Mirtazapine in social anxiety disorder: a pilot study.

Fourteen patients with social anxiety disorder (generalized type), according to DSM-IV criteria, were treated with mirtazapine 30 mg for 12 weeks. Twelve patients completed the study. Two patients (14.3%) dropped out due to side-effects. Generally, mirtazapine was well tolerated. Five out of 12 patients (41.7%) were classified as responders, based on a Clinical Global Improvement score of 1 or 2 and a reduction of the Liebowitz Social Anxiety Scale (LSAS) of 40%. The mean total score on the LSAS, as well as the anxiety and avoidance subscores, decreased significantly. This open pilot study suggests that further investigations are warranted to prove the efficacy of mirtazapine in generalized social anxiety disorder.

Adult↗