By what mechanism do indirect acting cholinergic drugs have an effect?
Indirect acting cholinergic drugs stimulate cholinergic receptors by inhibiting the re-uptake of ACH by inhibiting cholinesterases. Thus, indirect cholinergic drugs are also referred to as cholinesterase inhibitors or anticholinesterases.
What is the mechanism by which Pilocarpine and Nicotine work? What is the affect of each drug?
Pilocarpine is a direct acting muscarinic cholinergic receptor agonist. Pilocarpine increases salivation in salivary glands where muscarinic cholinergic receptors exist.
Nicotine is a direct acting nicotinic cholinergic agonist. Nicotine excites nicotinic m cholinergic receptors in skeletal muscle causing contraction.
How does physostigmine (esterin) increase salivation?
Physostigmine is a cholinesterase inhibitor (an indirect acting cholinergic drug) and thus increases synaptic levels of ACH at livary muscarinic receptors.