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Involvement of Presynaptic Histamine H 3 Receptors in the Modulation of Somatostatin Binding and Its Effects on Adenylyl Cyclase Activity in the Rat Frontoparietal Cortex
Author(s) -
Puebla Lilian,
Arilla Eduardo
Publication year - 1996
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1046/j.1471-4159.1996.66031051.x
Subject(s) - thioperamide , mepyramine , medicine , endocrinology , histamine , histamine h3 receptor , chemistry , somatostatin , histamine h2 receptor , histamine receptor , agonist , receptor , antagonist , biology
Thioperamide (2 mg/kg, i.p.), a histamine H 3 ‐receptor antagonist, increased the number of somatostatin (SS) receptors, with no change in the affinity constant, in the rat frontoparietal cortex. This effect was prevented by treatment with ( R )‐α‐methylhistamine (3.2 mg/kg, i.p.), a histamine H 3 ‐receptor agonist. Thioperamide also induced an increase in SS binding in rats pretreated with mepyramine, a histamine H 1 ‐receptor antagonist, or cimetidine, a histamine H 2 ‐receptor antagonist. Pretreatment with mepyramine plus cimetidine administered simultaneously antagonized the thioperamide effect on SS binding. The increase in the number of SS receptors was accompanied by a greater SS‐mediated inhibition of basal and forskolin‐stimulated adenylyl cyclase (AC) activity in frontoparietal cortical membranes in the thioperamide group. Furthermore, the functional activity of the guanine nucleotide‐binding inhibitory protein (G i protein) was not altered by thioperamide or ( R )‐α‐methylhistamine administration in frontoparietal cortical membranes. In rats treated with mepyramine plus thioperamide or cimetidine plus thioperamide, the increase in the number of SS receptors was also accompanied by an increased SS inhibition of AC activity. Thioperamide induced a significant increase in SS‐like immunoreactivity content in the frontoparietal cortex. Altogether, these results suggest that frontoparietal cortical histamine may play, at least in part, a role in the regulation of the somatostatinergic system.