Đang chuẩn bị liên kết để tải về tài liệu:
Understanding Drugs and Behaviour phần 5

Không đóng trình duyệt đến khi xuất hiện nút TẢI XUỐNG Tải xuống

nó trở nên rõ ràng neuropeptides và các amin có thể cùng tồn tại như là đồng-phát trong cùng một tế bào thần kinh với việc phát hành neuropeptide của điều chỉnhMa túy và hành động của họ | 122 Part II Non-medical Use of Psychoactive Drugs Table 9.1. Effects of GABA-ergic agents on the GABAA receptor and anxiety. Site of action Ligand Effect on anxiety GABA site GABA endogenous neurotransmitter Bicuculline antagonist BDZ site BDZs agonists b-carbolines inverse agonists Picrotoxin site Pentylenetetrazol Ethanol site Alcohol Neurosteroid site Neurosteroids agonists Barbiturate site Barbiturates agonists per 100 ml blood - see below disrupt thought processes self-restraint speech and movement. The main neuronal effect of alcohol is to disrupt the cellular membrane this decreases sodium and calcium ion influx depresses glutamate-linked channels and increases nicotinic acetylcholine and serotonin receptor binding Samson and Harris 1992 . The notion that alcohol has little neurotransmitter or regional specificity was first suggested by Schmiedeberg in the 1800s this led to the widespread view that alcohol had a general impairing effect on all cognitive processes and behaviours. This perspective was supported by the discovery that the main neurotransmitter target site for alcohol is the GABAa receptor which carries an ethanol-binding site Figure 9.1 . When alcohol binds to this receptor it causes an increase in the influx of chloride ions and a consequent decrease in the firing rate of postsynaptic cells. Since GABA is a ubiquitous inhibitory neurotransmitter this supported the notion of a generalised non-specific behavioural impairment. However alcohol also has somewhat less profound effects on dopamine opioids noradrenaline acetylcholine glutamate and serotonin systems although the balance of its effects does change with chronic as opposed to acute consumption. Furthermore there is increasing evidence that at physiologically realistic doses alcohol differentially affects different neurotransmitter systems in a regional and receptor-specific manner see White et al. 2000 for one view on this issue . These developments have been paralleled by studies showing