Effect of acute and repeated administration of 5-HT1A receptor agonists on 5-HT release in rat brain in vivo.
1. Electrophysiological measurements of 5-HT neuronal activity report that repeated administration of 5-HT1A receptor agonists leads to desensitization of the 5-HT1A autoreceptor but this has not yet been detected in measurements of brain 5-HT synthesis or metabolism. Here we have determined the effect of repeated administration of 5-HT1A receptor agonists on brain 5-HT release using microdialysis. 2. Acute administration of the 5-HT1A receptor agonists buspirone (0.1-5 mg/kg s.c.) and ipsapirone (0.03-3 mg/kg s.c.) caused a dose-dependent decrease in 5-HT output in ventral hippocampus of the chloral hydrate anaesthetized rat. 3. The 5-HT response to buspirone (0.1 and 0.5 mg/kg s.c.) and ipsapirone (0.3 mg/kg s.c.) was significantly inhibited by pre-treatment with the 5-HT1/beta-adrenoceptor antagonist pindolol (8-16 mg/kg s.c.). The 5-HT response to buspirone (0.1 mg/kg s.c.) and ipsapirone (0.3 mg/kg s.c.) was not blocked by pretreatment with a combination of the beta 1 and beta 2-adrenoceptor antagonists metoprolol and ICI 118,551 (4 mg/kg s.c.). 4. The effect of an acute challenge of buspirone (0.5 mg/kg s.c.) on 5-HT output in ventral hippocampus was not attenuated in rats treated twice daily for 14 days with 0.5 or 5 mg/kg s.c. buspirone compared to saline-injected controls. Similarly, the decrease in 5-HT induced by an acute challenge of ipsapirone (0.5 mg/kg s.c.) was not attenuated in rats treated twice daily for 14 days with 5 mg/kg s.c. ipsapirone.(ABSTRACT TRUNCATED AT 250 WORDS)
Sharp
T
T
MRC Clinical Pharmacology Unit, Radcliffe Infirmary, Oxford, UK.
McQuade
R
R
Bramwell
S
S
Hjorth
S
S
D017371:8-Hydroxy-2-(di-n-propylamino)tetralin / Q000494:pharmacology; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000818:Animals; D001923:Brain Chemistry / Q000187:drug effects*; D002065:Buspirone / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004567:Electrodes, Implanted; D004594:Electrophysiology; D006624:Hippocampus / Q000187:drug effects / Q000378:metabolism; D008297:Male; D017551:Microdialysis; D010869:Pindolol / Q000494:pharmacology; D011743:Pyrimidines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012701:Serotonin / Q000378:metabolism*; D017366:Serotonin Receptor Agonists / Q000494:pharmacology*
D000319:Adrenergic beta-Antagonists; D011743:Pyrimidines; D017366:Serotonin Receptor Agonists; D012701:Serotonin; C043077:ipsapirone; D017371:8-Hydroxy-2-(di-n-propylamino)tetralin; D010869:Pindolol; D002065:Buspirone