Page 291 - Basic _ Clinical Pharmacology ( PDFDrive )

SECTION IV DRUGS WITH IMPORTANT ACTIONS ON

SMOOTH MUSCLE

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Histamine, Serotonin,

& the Ergot Alkaloids

Bertram G. Katzung, MD, PhD

C ASE STUD Y

A healthy 45-year-old physician attending a reunion in a signs and symptoms with marked orthostatic hypotension.
vacation hotel developed dizziness, redness of the skin over The menu included a green salad, sautéed fish with rice, and
the head and chest, and tachycardia while eating. A short apple pie. What is the probable diagnosis? How would you
time later, another physician at the table developed similar treat these patients?

It has long been known that many tissues contain substances Because of their broad and largely undesirable peripheral
that, when released by various stimuli, cause physiologic effects effects, neither histamine nor serotonin has any clinical applica-
such as reddening of the skin, pain or itching, and broncho- tion in the treatment of disease. However, compounds that
spasm. Later, it was discovered that many of these substances selectively activate certain receptor subtypes or selectively antago-
are also present in nervous tissue and have multiple functions. nize the actions of these amines are of considerable clinical value.
Histamine and serotonin (5-hydroxytryptamine, 5-HT) are bio- This chapter therefore emphasizes the basic pharmacology of the
logically active amines that function as neurotransmitters and are agonist amines and the clinical pharmacology of the more selective
also found in non-neural tissues, have complex physiologic and agonist and antagonist drugs. Obesity, a poorly understood condi-
pathologic effects through multiple receptor subtypes, and are tion, appears to involve many receptors, including some histamine
often released locally. Together with endogenous peptides (see and serotonin receptors. It is discussed in a special section following
Chapter 17), prostaglandins and leukotrienes (see Chapter 18), the discussion of serotonin and its antagonists. The ergot alkaloids,
and cytokines (see Chapter 55), they constitute the autacoid compounds with partial agonist activity at serotonin and several
group of drugs. other receptors, are discussed at the end of the chapter.

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