Evidence that the lateral tegmental field plays an important role in the central sympathoinhibitory action of 8-OH-DPAT.
We examined the effects of 8-OH-DPAT and 5-HT on three types of sympathetic-related neurons identified in the lateral tegmental field of anesthetized cats using spike-triggered averaging techniques. Based on their response to baroreceptor activation, these neurons could be classified as sympathoexcitatory, sympathoinhibitory, or baroreceptor activation unresponsive. 8-OH-DPAT administered intravenously was found to inhibit sympathoexcitatory neurons with a high degree of correlation to inhibition of sympathetic activity, and to excite sympathoinhibitory neurons in a dose-dependent manner. Iontophoretic application of 8-OH-DPAT and 5-HT to the majority of sympathoexcitatory neurons caused inhibition of spontaneous activity while iontophoretic application of 8-OH-DPAT to sympathoinhibitory neurons had variable effects although 5-HT consistently caused excitation. Baroreceptor unresponsive neurons were insensitive to iontophoretic 8-OH-DPAT and showed only limited response to 5-HT. It is concluded that the lateral tegmental field plays an important role in the sympathoinhibitory action of 8-OH-DPAT.
Clement
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Cardiovascular Diseases Research, Upjohn Company, Kalamazoo, MI 49001.
McCall
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D017371:8-Hydroxy-2-(di-n-propylamino)tetralin; D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D001011:Aorta / Q000502:physiology; D002415:Cats; D007275:Injections, Intravenous; D007478:Iontophoresis; D009474:Neurons / Q000187:drug effects; D011311:Pressoreceptors / Q000187:drug effects; D012701:Serotonin / Q000494:pharmacology; D013565:Sympatholytics / Q000494:pharmacology*; D013681:Tegmentum Mesencephali / Q000502:physiology*; D013764:Tetrahydronaphthalenes / Q000494:pharmacology*
D013565:Sympatholytics; D013764:Tetrahydronaphthalenes; D012701:Serotonin; D017371:8-Hydroxy-2-(di-n-propylamino)tetralin