Neurotransmitter system cholinergic systems

The reported neurochemical effects of lead are, as has been seen, enormous. They can be broadly summarized by neurotransmitter system cholinergic impairment at relatively high levels (usually in the presence of non-specific effects), dopaminergic effects at low levels, and impairment at higher levels (in the presence of obvious non-specific effects), GABAergic effects at levels where a complication from the interaction with D-amino laevulinic acid also occurs. There is also a mixed bag of effects on enkephalin, adenyl cyclase, 5-hydroxytrypamine and other putative aminergic neurotransmitters. 

One problem with both these theories is that disruption of noradrenergic transmission by selective adrenoceptor antagonists has little impact on the development of escape deficits. However, such antagonists do prevent the reversal of learned helplessness by antidepressants (reviewed by Stanford 1995). Also, it would be most unlikely that a deficit in only one neurotransmitter system fully accounts for learned helplessness. Indeed, there is plenty of evidence for a role for 5-HT in learned helplessness for instance, this behaviour is reversed by microinjection of 5-HT into the prefrontal cortex (Davis et al. 1999). Finally, it is clear that opioid, GABAergic and cholinergic systems (among others) are all linked with this behavioural deficit and even dihydropyridine antagonists of Ca + channels prevent its development. 

Cory-Slechta DA. 1995a. Relationships between lead-induced learning impairments and changes in dopaminergic, cholinergic, and glutamatergic neurotransmitter system functions. Annu Rev Pharmacol Toxicol 35 391-415. 

Muscarinic receptors have modulatory effects on numerous other neurotransmitters in the brain (van der Zee and Luiten 1999). Of particular interest are interactions between glutamate and cholinergic systems in learning and memory (Aigner 1995). 

The permissive, adrenergic-cholinergic balance, and bidimensional hypotheses, based on both the effects of antidepressants and on the modulating interactions among various neurotransmitter systems... 

We will proceed with this neurotransmitter system much as we did with the cholinergic system. Keep in mind that the main neurotransmitter here is norepinephrine and that adrenergic neurons are found in the sympathetic (fight or flight) portion ofthe autonomic, peripheral nervous system. 

The parasympathetic system is exclusively a cholinergic system. The neurotransmitter acetylcholine is produced at both pre- and post-ganglionic nerve cells. Acetylcholine is the neurotransmitter at the preganglionic neurons of the sympathetic system also, but the postganglionic sympathetic stimulation is by norepinephrine. 

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