Effect of chronic serotonin-2 receptor agonist or antagonist administration on serotonin-1A receptor sensitivity.
We have investigated the effect of 5-HT2 receptor agonist or antagonist administration on postsynaptic 5-HT1A receptor sensitivity assessed by two behavioral measures, reciprocal forepaw treading or hypothermia induced by acute injection of the 5-HT1A receptor agonist 8-OH-DPAT. The effectiveness of these drug treatments to downregulate 5-HT2A receptors was confirmed by measuring the binding of [3H]-ketanserin in cortical homogenates, because all of these drug treatments have been shown to result in the downregulation of 5-HT2A receptor sites. Acute or chronic treatment of rats with the 5-HT2 receptor antagonist mianserin, or chronic administration of the 5-HT2A receptor antagonist ketanserin, did not alter 8-OH-DPAT-induced hypothermia or forepaw treading. These data indicate that downregulation of 5-HT2A receptors is not sufficient to alter these postsynaptic 5-HT1A receptor-mediated responses. Chronic treatment of rats with the 5-HT2 receptor agonist DOI, however, resulted in the attenuation of both 5-HT1A receptor-mediated responses measured in separate experimental groups. The apparent desensitization of 5-HT1A receptors following chronic DOI treatment was not accompanied by a change in either the number or affinity of 5-HT1A receptor sites as measured by the binding of [3H]-8-OH-DPAT in hippocampal homogenates. Chronic activation of 5-HT2 receptors may be one mechanism by which the sensitivity postsynaptic 5-HT1A receptors can be regulated.
Hensler
J G
JG
Department of Pharmacology, University of Texas Health Science Center, San Antonio 78284-7764, USA.
Truett
K A
KA
D017371:8-Hydroxy-2-(di-n-propylamino)tetralin / Q000494:pharmacology; D000818:Animals; D002540:Cerebral Cortex / Q000187:drug effects* / Q000502:physiology; D007035:Hypothermia / Q000139:chemically induced / Q000503:physiopathology; D007650:Ketanserin / Q000378:metabolism; D008297:Male; D009043:Motor Activity / Q000187:drug effects / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D011985:Receptors, Serotonin / Q000187:drug effects* / Q000502:physiology*; D044263:Receptors, Serotonin, 5-HT1; D018490:Serotonin Agents / Q000494:pharmacology*
D011985:Receptors, Serotonin; D044263:Receptors, Serotonin, 5-HT1; D018490:Serotonin Agents; D017371:8-Hydroxy-2-(di-n-propylamino)tetralin; D007650:Ketanserin