also remember that drugs designed to target CNS receptors can have systemic side
effects and that drugs targeting systemic problems can have CNS side effects.
4.6.4.3 H 3 Antagonists
Several lines of evidence suggest a role for H 3 receptors in cognitive processes. The use
of H 3 antagonists in learning and memory disorders has been suggested. Thioperamide,
a prototypic H 3 antagonist, enhances arousal patterns in cats, an observation which has
been confirmed using other nonthiourea H 3 blockers.
4.6.5 The Clinical–Molecular Interface: The Many Uses and
Abuses of H 1 Receptor AntagonistsH 1 receptor antagonists (antihistamines) are among the most widely used therapeutic
agents. Indeed, sometimes the exact same molecule (e.g., diphenhydramine) is mar-
keted in different aisles in the same pharmacy under many brand names for different
NEUROTRANSMITTERS AND THEIR RECEPTORS 269