{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,25]],"date-time":"2026-08-25T06:12:27Z","timestamp":1787638347008,"version":"build-2736575974"},"reference-count":23,"publisher":"American Physiological Society","issue":"1","content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["American Journal of Physiology-Regulatory, Integrative and Comparative Physiology"],"published-print":{"date-parts":[[2008,1]]},"abstract":"<jats:p> To better understand the central mechanisms that mediate increases in heart rate (HR) during psychological stress, we examined the effects of systemic and intramedullary (raphe region) administration of the serotonin-1A (5-HT<jats:sub>1A<\/jats:sub>) receptor agonist 8-hydroxy-2-(di- n-propylamino)tetraline (8-OH-DPAT) on cardiac changes elicited by restraint in hooded Wistar rats with preimplanted ECG telemetric transmitters. 8-OH-DPAT reduced basal HR from 356 \u00b1 12 to 284 \u00b1 12 beats\/min, predominantly via a nonadrenergic, noncholinergic mechanism. Restraint stress caused tachycardia (an initial transient increase from 318 \u00b1 3 to 492 \u00b1 21 beats\/min with a sustained component of 379 \u00b1 12 beats\/min). \u03b2-Adrenoreceptor blockade with atenolol suppressed the sustained component, whereas muscarinic blockade with methylscopolamine (50 \u03bcg\/kg) abolished the initial transient increase, indicating that sympathetic activation and vagal withdrawal were responsible for the tachycardia. Systemic administration of 8-OH-DPAT (10, 30, and 100 \u03bcg\/kg) attenuated stress-induced tachycardia in a dose-dependent manner, and this effect was suppressed by the 5-HT<jats:sub>1A<\/jats:sub> antagonist WAY-100635 (100 \u03bcg\/kg). Given alone, the antagonist had no effect. Systemically injected 8-OH-DPAT (100 \u03bcg\/kg) attenuated the sympathetically mediated sustained component (from +85 \u00b1 19 to +32 \u00b1 9 beats\/min) and the vagally mediated transient (from +62 \u00b1 5 to +25 \u00b1 3 beats\/min). Activation of 5-HT<jats:sub>1A<\/jats:sub> receptors in the medullary raphe by microinjection of 8-OH-DPAT mimicked the antitachycardic effect of the systemically administered drug but did not affect basal HR. We conclude that tachycardia induced by restraint stress is due to a sustained increase in cardiac sympathetic activity associated with a transient vagal withdrawal. Activation of central 5-HT<jats:sub>1A<\/jats:sub> receptors attenuates this tachycardia by suppressing autonomic effects. At least some of the relevant receptors are located in the medullary raphe-parapyramidal area. <\/jats:p>","DOI":"10.1152\/ajpregu.00464.2007","type":"journal-article","created":{"date-parts":[[2007,10,24]],"date-time":"2007-10-24T23:00:42Z","timestamp":1193266842000},"page":"R132-R141","source":"Crossref","is-referenced-by-count":40,"title":["Activation of 5-HT<sub>1A<\/sub> receptors attenuates tachycardia induced by restraint stress in rats"],"prefix":"10.1152","volume":"294","author":[{"given":"Sukonthar","family":"Ngampramuan","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Mathias","family":"Baumert","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Mirza Irfan","family":"Beig","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Naiphinich","family":"Kotchabhakdi","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Eugene","family":"Nalivaiko","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"24","reference":[{"key":"R1","doi-asserted-by":"publisher","DOI":"10.1016\/0165-1838(89)90090-8"},{"key":"R2","doi-asserted-by":"publisher","DOI":"10.1038\/sj.bjp.0702908"},{"key":"R3","doi-asserted-by":"publisher","DOI":"10.1016\/0014-2999(92)94831-F"},{"key":"R4","doi-asserted-by":"crossref","unstructured":"Carrive P. 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