Locus coeruleus-mediated inhibition of chemosensory responses in the rat nucleus tractus solitarius is mediated by alpha2-adrenoreceptors.
It is known that electrical and L-glutamate stimulation of the locus coeruleus (LC) reduce the multiunit activity evoked in the nucleus of the tractus solitarius (NTS) by cyanoboro-hydride. In the present study, rats anaesthetised with urethane were microinjected with noradrenergic antagonists into the NTS, to test whether the inhibitory effects of LC stimulation on cyanide-evoked discharge in the NTS were mediated by noradrenaline. Microinjection of yohimbine into the NTS (0.2, 0.6, 1.8, 5.4 nmol) induced dose-dependent reduction of the inhibitory effect of LC stimulation on NTS neurones, while prazosin produced no effect. The results indicate that LC-induced inhibition of the cyanide-evoked discharge in the NTS is mediated by endogenous noradrenaline release acting on alpha2-adrenoreceptors.
Unit of Neurophysiology and Biophysics, Institute of Nutrition and Food Technology (INTA), University of Chile, Santiago.
H
H
Pérez
S
S
Ruiz
C
C
Laurido
A
A
Hernández
D058669:Adrenergic alpha-2 Receptor Antagonists; D000317:Adrenergic alpha-Antagonists / Q000008:administration & dosage / Q000494:pharmacology; D000818:Animals; D001894:Borohydrides / Q000494:pharmacology; D002628:Chemoreceptor Cells / Q000502:physiology*; D004558:Electric Stimulation; D008125:Locus Coeruleus / Q000187:drug effects / Q000502:physiology*; D008297:Male; D008845:Microinjections; D009433:Neural Inhibition / Q000502:physiology*; D009474:Neurons / Q000187:drug effects / Q000502:physiology; D009638:Norepinephrine / Q000502:physiology; D011224:Prazosin / Q000008:administration & dosage / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D018341:Receptors, Adrenergic, alpha-2 / Q000502:physiology*; D017552:Solitary Nucleus / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D015016:Yohimbine / Q000008:administration & dosage / Q000494:pharmacology
D058669:Adrenergic alpha-2 Receptor Antagonists; D000317:Adrenergic alpha-Antagonists; D001894:Borohydrides; D018341:Receptors, Adrenergic, alpha-2; D015016:Yohimbine; C009282:sodium cyanoborohydride; D009638:Norepinephrine; D011224:Prazosin