NEUROTRANSMITTERS AND THEIR RECEPTORS
263
the blood–brain barrier, central receptors can use only the locally synthesized
histamine. Occupation of the H 1 receptor by an agonist does not activate adenylate
cyclase (AC); it appears to use phosphoinositol as second messenger. H 1 receptors
are not very specific and are occupied by antidepressants and neuroleptics as well.
This explains the sedative effect of all three classes of drugs. The H 1 receptors are
easily solubilized and have been purified on lectin affinity columns, indicating their
glycoprotein nature.
Figure 4.11 Histamine metabolism.
263
the blood–brain barrier, central receptors can use only the locally synthesized
histamine. Occupation of the H 1 receptor by an agonist does not activate adenylate
cyclase (AC); it appears to use phosphoinositol as second messenger. H 1 receptors
are not very specific and are occupied by antidepressants and neuroleptics as well.
This explains the sedative effect of all three classes of drugs. The H 1 receptors are
easily solubilized and have been purified on lectin affinity columns, indicating their
glycoprotein nature.
Figure 4.11 Histamine metabolism.