Dopaminergic excitation of the goat carotid body is mediated by the serotonin type 3 receptor subtype.
The purpose of the present study was to use chemoafferent recordings from the goat carotid body (CB) to pharmacologically identify the putative low affinity excitatory receptor for dopamine (DA). Close arterial injections of DA (1-50 microg kg(-1)) induced a dose-dependent excitatory burst followed by inhibition of the CB chemoafferent activity. The inhibition is likely DA D(2) receptor-mediated as it was blocked by domperidone (0.5-1.0 mg kg(-1) iv). The initial high frequency burst of CB chemoafferent activity could not be attenuated by selective antagonists for the DA D(1-4) receptors but could be blocked by D-tubocurarine or the selective serotonin(3) (5-HT(3)) receptor antagonists, tropisetron and MDL72222. The selective nicotinic antagonists, hexamethonium and vecuronium, were without effect. Selective blockade of the 5-HT(3)-receptor subtype using tropisetron significantly reduced both normoxic and hypoxic unitary CB discharge. These results suggest that DA-mediated excitation of the goat CB chemosensitive afferents occurs via the 5-HT(3)-receptor subtype and that the 5-HT(3)-receptor may exert an excitatory modulation of CB output during normal physiological responses in the goat.
Herman
Jay K
JK
Covance Laboratories, Inc., 3301 Kinsman Boulevard, Madison, WI 53704, USA.
O'Halloran
Ken D
KD
Janssen
Patrick L
PL
Bisgard
Gerald E
GE
D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000704:Analysis of Variance; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology; D002344:Carotid Body / Q000187:drug effects / Q000502:physiology*; D002346:Carotid Sinus / Q000294:innervation / Q000503:physiopathology; D003485:Cyanates / Q000494:pharmacology; D004294:Domperidone / Q000494:pharmacology; D004298:Dopamine / Q000502:physiology*; D018492:Dopamine Antagonists / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005260:Female; D005731:Ganglionic Stimulants / Q000494:pharmacology; D006041:Goats; D007211:Indoles / Q000494:pharmacology; D008297:Male; D009412:Nerve Fibers / Q000187:drug effects / Q000502:physiology; D009433:Neural Inhibition / Q000187:drug effects; D009538:Nicotine / Q000494:pharmacology; D009636:Norbornanes; D009919:Orchiectomy; D011985:Receptors, Serotonin / Q000502:physiology*; D044406:Receptors, Serotonin, 5-HT3; D012701:Serotonin / Q000494:pharmacology; D012702:Serotonin Antagonists / Q000494:pharmacology; D017366:Serotonin Receptor Agonists / Q000494:pharmacology; D000077526:Tropisetron
D003485:Cyanates; D018492:Dopamine Antagonists; D005731:Ganglionic Stimulants; D007211:Indoles; D009636:Norbornanes; D011985:Receptors, Serotonin; D044406:Receptors, Serotonin, 5-HT3; D012702:Serotonin Antagonists; D017366:Serotonin Receptor Agonists; D012701:Serotonin; D004294:Domperidone; D000077526:Tropisetron; D009538:Nicotine; C009281:sodium cyanate; C020900:fencamfamine; D004298:Dopamine