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Post-Traumatic Stress Disorder                          

 

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·     Slopien A, Dmitrzak-Weglarz M, Rybakowski F  Rajewski A, Hauser J.

Klinika Psychiatrii Dzieci i Mlodziezy AM w Poznaniu.

Attention-deficit hyperactivity disorder (ADHD) begins in early childhood. In this article we review the studies supporting a genetic background of this disorder. ADHD occurs in 3-10% of the general population. Family studies reveal a 5 times more likely frequency of ADHD among first-degree relatives than in the general population. Monozygotic twin concordance rate for ADHD is 81%, whereas for dizygotic twins it is 29%. One of the ADHD predisposing factors is dopaminergic neurotransmission abnormality. According to other studies there is a relationship between polymorphism of dopamine transporter gene (DAT), dopamine receptors genes: DRD2, DRD3, DRD4, DRD5, dopamine-beta-hydroxylase gene (DBH) and catechol-O-methyltransferase gene (COMT) and ADHD. In other articles authors describe abnormalities of the serotonergic system, such as the polymorphism of the serotonin transporter gene (5HTT/SERT), serotonin receptors genes 5HT2A and 5HT1B in the development ofADHD. Another possible factor in ADHD background is the dysregulation of the adrenergic system. The most frequently studied is the connection between polymorphism of norepinephrine transporter gene (NET), adrenergic receptors genes: alpha 2A (ADRA2A), alpha 1C (ADRA1C), alpha 2C and monoamine oxidase A gene (MAO-A).

PMID: 16756025 [PubMed - in process]

: Proc Natl Acad Sci U S A. 2006 May 23;103(21):8251-6. Epub 2006 May 12.Click here to read  Links

Frequency-specific and D2 receptor-mediated inhibition of glutamate release by retrograde endocannabinoid signaling.

·     Yin HH, Lovinger DM.

Laboratory for Integrative Neuroscience, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, MD 20892, USA.

The mechanisms underlying modulation of corticostriatal synaptic transmission by D2-like receptors (D2Rs) have been controversial. A recent study suggested that D2Rs inhibit glutamate release at this synapse, but only during high-frequency synaptic activation. Because the release of postsynaptic endocannabinoids (eCBs), which act as retrograde messengers to inhibit presynaptic glutamate release, can be triggered by D2R activation and intense synaptic activation, such a mechanism could mediate dopaminergic modulation of corticostriatal transmission. Here, we show that D2R activation reduces excitatory transmission onto striatal medium spiny neurons at a stimulation frequency of 20 Hz but not at 1 Hz. This form of inhibition requires CB1 receptor activation, as evidenced by the fact that it is blocked by AM251 [N-(piperidin-1-yl)-1-(2,4-dichlorophenyl)-5-(4-chlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide], a CB1 antagonist, and is absent in CB1 knockout mice. It is also blocked by postsynaptic intracellular calcium chelation, by group I metabotropic glutamate receptor antagonism, and by inhibition of postsynaptic phospholipase C. These results demonstrate a previously unrecognized role for retrograde eCB signaling in reversible and frequency-specific inhibition of glutamate release by the activation of striatal D2Rs.

PMID: 16698932 [PubMed - indexed for MEDLINE]

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