title: Evidence that the putative 5-HT1A receptor agonists, 8-OH-DPAT and ipsapirone, have a central hypotensive action that differs from that of clonidine in anaesthetised cats.
abstract: Thoracic preganglionic sympathetic nerve activity, blood pressure, heart rate and femoral arterial conductance were recorded in anaesthetised, paralysed cats. Cumulative dose-response curves were constructed for 8-OH-DPAT, ipsapirone and clonidine. All three drugs caused dose-related falls in blood pressure which were associated with minimal changes in femoral arterial conductance. However, 8-OH-DPAT and ipsapirone differed from clonidine in that their hypotensive action was associated with moderate sympathoinhibition and a profound bradycardia, whereas clonidine caused profound sympathoinhibition and, as it did not increase central vagal tone, only a moderate bradycardia. 8-OH-DPAT also caused sympathoinhibition in bi-vagotomised cats and decreased carotid sinus nerve activity along with blood pressure. As 8-OH-DPAT and ipsapirone bind selectively to central 5-HT1A receptors it is concluded that central stimulation of these receptors causes sympathoinhibition and an increase in vagal tone, whereas stimulation of central alpha 2-adrenoceptors causes only sympathoinhibition. In addition, the present data suggest a peripheral vasodilator mechanism may also contribute to the hypotensive effects of 8-OH-DPAT and ipsapirone in the cat. The nature and relative importance of this remains to be established.
mesh_terms: D017371:8-Hydroxy-2-(di-n-propylamino)tetralin; D000758:Anesthesia; D000818:Animals; D000959:Antihypertensive Agents; D001285:Atropine / Q000494:pharmacology; D001794:Blood Pressure / Q000187:drug effects; D002415:Cats; D003000:Clonidine / Q000494:pharmacology*; D004146:Dioxanes / Q000494:pharmacology; D006339:Heart Rate / Q000187:drug effects; D019329:Idazoxan; D008297:Male; D009281:Naphthalenes / Q000494:pharmacology*; D009474:Neurons / Q000378:metabolism; D011743:Pyrimidines / Q000494:pharmacology*; D011985:Receptors, Serotonin / Q000187:drug effects*; D013564:Sympathetic Nervous System / Q000378:metabolism; D013764:Tetrahydronaphthalenes / Q000494:pharmacology*; D014294:Trimethaphan / Q000494:pharmacology; D014628:Vagotomy
chemical_list: D000959:Antihypertensive Agents; D004146:Dioxanes; D009281:Naphthalenes; D011743:Pyrimidines; D011985:Receptors, Serotonin; D013764:Tetrahydronaphthalenes; D014294:Trimethaphan; C043077:ipsapirone; D017371:8-Hydroxy-2-(di-n-propylamino)tetralin; D001285:Atropine; D003000:Clonidine; D019329:Idazoxan