| 20045083 |
McDonald MD, Gilmour KM, Walsh PJ, Perry SF: Cardiovascular and respiratory reflexes of the gulf toadfish (Opsanus beta) during acute hypoxia. Respir Physiol Neurobiol. 2010 Jan 31;170(1):59-66. Epub 2010 Jan 5.
The acute cardiovascular and respiratory responses of the gulf toadfish, Opsanus beta, to acute hypoxia or exposure to the O (2) chemoreceptor stimulant, sodium cyanide (NaCN) were characterized and the role of serotonin type 2 (5-HT (2)) receptors in mediating these responses was investigated. Toadfish responded to hypoxia or NaCN exposure with a decrease in heart rate (fH) and an increase in breathing amplitude (V (AMP)) but no change in breathing frequency (fR). The bradycardia appeared to be mediated to some extent by 5-HT (2) receptors, as methysergide, a non-selective 5-HT (1/2) receptor antagonist, and ketanserin, a 5-HT (2) receptor antagonist, attenuated the response. Injection of alpha-methyl-5-HT, a 5-HT (2) agonist, also resulted in bradycardia that was inhibited by ketanserin, lending further support for 5-HT (2) receptor involvement, possibly 5-HT (2A) or 5-HT (2C), in the regulation of fH. External NaCN exposure resulted in a significant decrease in caudal arterial blood pressure (P (CA)) that was attenuated by methysergide. In contrast, injection with alpha-methyl-5-HT resulted in a substantial increase in P (CA) that was not affected by ketanserin, suggesting the possible involvement of 5-HT (2B) or 5-HT (2C) receptors. These data are the first to suggest a unique distribution of 5-HT (2B/2C) receptors may be involved in mediating vasoconstriction of the systemic vasculature of toadfish. These data also provide mechanistic support for why pulsatile urea excretion, believed to be regulated by 5-HT via the toadfish 5-HT (2A) receptor, is not triggered by hypoxia or external chemoreceptor activation. |
33(0,1,1,3) |