Biochemical events coupled to the activation of serotonin receptors in brain regions of the rat.
Effects of serotonin on the levels of inositol phosphate and cyclic AMP in certain brain regions of the rat were studied. When brain slices were treated with serotonin (10(-4) or 10(-5) M), it caused significant increases in inositol phosphate levels in cerebral cortex, hippocampus, midbrain and brain stem, but not in cerebellum. Serotonin itself did not have a significant effect on the basal levels of cAMP in most of these regions, except in midbrain in which it had stimulatory effect. However, serotonin also had significant inhibitory effect on forskolin-induced cAMP formation in cerebral cortex, hippocampus and brain stem but not in midbrain in which an increase instead. Effects of serotonin on both biochemical events were in dose-dependent manner, and their maximal responses were at doses between 10(-4) and 10(-3) M. The rank order of the maximal response to serotonin on inositol phosphate production in these regions was cerebral cortex greater than hippocampus greater than midbrain greater than brain stem greater than cerebellum. On the other hand, the rank order of the maximal response to serotonin on inhibiting forskolin-induced cAMP formation was cerebral cortex = brain stem greater than hippocampus. Our data revealed that there is a regional difference in serotonin-induced inositol phosphate and cAMP responses. This difference is likely due to a differential distribution of serotonergic receptor subtypes and densities in different regions of rat brain.
Wei
J W
JW
Institute of Neurosciences, National Yang-Ming Medical College, Taipei, Taiwan, Republic of China.
Lee
M J
MJ
Yeh
S R
SR
D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D001921:Brain / Q000033:anatomy & histology; D001923:Brain Chemistry / Q000502:physiology*; D002217:Carbachol / Q000494:pharmacology; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000096:biosynthesis; D066298:In Vitro Techniques; D010716:Phosphatidylinositols / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D011985:Receptors, Serotonin / Q000378:metabolism*; D015290:Second Messenger Systems / Q000502:physiology*; D012701:Serotonin / Q000494:pharmacology
D010716:Phosphatidylinositols; D011985:Receptors, Serotonin; D005576:Colforsin; D012701:Serotonin; D002217:Carbachol; D000242:Cyclic AMP; D000262:Adenylyl Cyclases