synthesis and in vitro pharmacology of a series of histamine h2 ...

Chapter 1
3) N-type channels are found in neurones and may regulate neurotransmitter
release. Like P-type channels, they have an intermediate single-channel conductance
compared to L- or T-type channels. N-type channels are highly
sensitive to co-conotoxins.
4) P-type channels, like L- and N-type channels, are high voltage activated Ca 2+
-
channels. P-type channels are located in cerebellar Purkinje cells and may be
responsible for neurotransmitter release in many brain regions.
In vascular smooth muscle cells, calcium influx mainly takes place via specific L-type
Ca 2+
-channels and to a lesser extent via the Na +
/Ca 2+
-exchange process.
Several exogenous ligands exist which can selectively block Ca 2+
-entry through Ltype
calcium channels. These ligands can be classified according to several criteria,
based upon: chemistry, specificity on calcium current inhibition and tissue selectivity /
clinical usage 72
.
In this chapter the chemical criterion is used to define the classes of CCBs (fig. 9f):
- phenylalkylamines, like verapamil 55
- benzodiazepines, like diltiazem 56
- dihydropyridines (DHPs), like nifedipine 57
57 Nifedipine 58 Nicardipine
Figure 9f: Antihypertensives; calcium channel blockers
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