In this Chapter:
4.1. Drugs stimulating adrenoceptors (adrenomimetics)
4.1.1. Drugs stimulating α- and β-adrenoceptors (α-, β-adrenomimetics)
4.1.2. Drugs stimulating mostly α-adrenoceptors (α-adrenomimetics)
4.1.3. Drugs stimulating mostly β-adrenoceptors ( β -adrenomimetics)
4.2. Drugs blocking adrenoceptors (adrenoceptor antagonists)
4.2.1. Drugs blocking α-adrenoceptors (α-adrenoblockers)
4.2.2. Drugs blocking β-adrenoceptors (β-adrenoblockers)
4.2.3. Drugs blocking α- and β-adrenoceptors (α-, β-adrenoblockers)
4.3. Drugs of presynaptic action
4.3.1. Sympathomimetics (adrenomimetics of indirect action)
4.3.2. Sympatholytics (drugs inhibiting the transmission from adrenergic fiber terminals)
In the adrenergic synapses the transmission is mediated by norepinephrine. Within the peripheral nervous system norepinephrine participates in the transmission of impulses from the adrenergic fibres to the effector cells (see Fig. 2.2).
Adrenergic axons, approaching the effector cell, divide into a thin net of fibres with varicosities, that function as nerve terminals. The latter participate in the formation of synaptic contacts with the effector cells (Fig. 4.1). Varicosities contain vesicles with neurotransmitter norepinephrine.
The biosynthesis of norepinephrine from tyrosine occurs in the adrenergic neurons with a number of enzymes being involved. Formation of DOPA and dopamine takes place in the cytoplasm of neurons, and norepinephrine is formed in the vesicles. Below are the biosynthesis pathways of dopamine, norepinephrine and epinephrine (Fig. 4.2).
Nerve impulses induce the release of norepinephrine into the synaptic gap, followed by its interaction with the adrenoceptors of the postsynaptic membrane. Adrenoceptors, pres-