Biomaterial Database

Evidence for involvement of alpha 2-adrenoceptors in the nucleus ambiguous in baroreflex-mediated bradycardia. 1983

S Gurtu, and D K Sharma, and J N Sinha, and K P Bhargava

Microinjection of noradrenaline and clonidine into the nucleus ambiguus elicited dose-dependent bradycardia with insignificant alteration of blood pressure. Phenylephrine failed to elicit any cardiovascular effect. The bradycardic effects of noradrenaline and clonidine were antagonized by piperoxan but not by phenoxybenzamine. Adrenergic neurone blockade with local guanethidine pretreatment also abolished the response to clonidine. No significant cardiovascular effect of clonidine microinjection into the nucleus ambiguus was observed in bilaterally vagotomized animals. The baroreflex bradycardia induced by volume loading as abolished by yohimbine and piperoxan but not by phenoxybenzamine, microinjected bilaterally into the nucleus ambiguus. These results demonstrate the presence of cardioinhibitory, presynaptic alpha 2-adrenoceptors in the nucleus ambiguus and their involvement in baroreflex bradycardia.

UI	MeSH Term	Description	Entries
D008297	Male		Males
D008526	Medulla Oblongata	The lower portion of the BRAIN STEM. It is inferior to the PONS and anterior to the CEREBELLUM. Medulla oblongata serves as a relay station between the brain and the spinal cord, and contains centers for regulating respiratory, vasomotor, cardiac, and reflex activities.	Accessory Cuneate Nucleus,Ambiguous Nucleus,Arcuate Nucleus of the Medulla,Arcuate Nucleus-1,External Cuneate Nucleus,Lateral Cuneate Nucleus,Nucleus Ambiguus,Ambiguus, Nucleus,Arcuate Nucleus 1,Arcuate Nucleus-1s,Cuneate Nucleus, Accessory,Cuneate Nucleus, External,Cuneate Nucleus, Lateral,Medulla Oblongatas,Nucleus, Accessory Cuneate,Nucleus, Ambiguous,Nucleus, External Cuneate,Nucleus, Lateral Cuneate
D008845	Microinjections	The injection of very small amounts of fluid, often with the aid of a microscope and microsyringes.	Microinjection
D009638	Norepinephrine	Precursor of epinephrine that is secreted by the ADRENAL MEDULLA and is a widespread central and autonomic neurotransmitter. Norepinephrine is the principal transmitter of most postganglionic sympathetic fibers, and of the diffuse projection system in the brain that arises from the LOCUS CERULEUS. It is also found in plants and is used pharmacologically as a sympathomimetic.	Levarterenol,Levonorepinephrine,Noradrenaline,Arterenol,Levonor,Levophed,Levophed Bitartrate,Noradrenaline Bitartrate,Noradrénaline tartrate renaudin,Norepinephrin d-Tartrate (1:1),Norepinephrine Bitartrate,Norepinephrine Hydrochloride,Norepinephrine Hydrochloride, (+)-Isomer,Norepinephrine Hydrochloride, (+,-)-Isomer,Norepinephrine d-Tartrate (1:1),Norepinephrine l-Tartrate (1:1),Norepinephrine l-Tartrate (1:1), (+,-)-Isomer,Norepinephrine l-Tartrate (1:1), Monohydrate,Norepinephrine l-Tartrate (1:1), Monohydrate, (+)-Isomer,Norepinephrine l-Tartrate (1:2),Norepinephrine l-Tartrate, (+)-Isomer,Norepinephrine, (+)-Isomer,Norepinephrine, (+,-)-Isomer
D011311	Pressoreceptors	Receptors in the vascular system, particularly the aorta and carotid sinus, which are sensitive to stretch of the vessel walls.	Baroreceptors,Receptors, Stretch, Arterial,Receptors, Stretch, Vascular,Stretch Receptors, Arterial,Stretch Receptors, Vascular,Arterial Stretch Receptor,Arterial Stretch Receptors,Baroreceptor,Pressoreceptor,Receptor, Arterial Stretch,Receptor, Vascular Stretch,Receptors, Arterial Stretch,Receptors, Vascular Stretch,Stretch Receptor, Arterial,Stretch Receptor, Vascular,Vascular Stretch Receptor,Vascular Stretch Receptors
D011942	Receptors, Adrenergic, alpha	One of the two major pharmacological subdivisions of adrenergic receptors that were originally defined by the relative potencies of various adrenergic compounds. The alpha receptors were initially described as excitatory receptors that post-junctionally stimulate SMOOTH MUSCLE contraction. However, further analysis has revealed a more complex picture involving several alpha receptor subtypes and their involvement in feedback regulation.	Adrenergic alpha-Receptor,Adrenergic alpha-Receptors,Receptors, alpha-Adrenergic,alpha-Adrenergic Receptor,alpha-Adrenergic Receptors,Receptor, Adrenergic, alpha,Adrenergic alpha Receptor,Adrenergic alpha Receptors,Receptor, alpha-Adrenergic,Receptors, alpha Adrenergic,alpha Adrenergic Receptor,alpha Adrenergic Receptors,alpha-Receptor, Adrenergic,alpha-Receptors, Adrenergic
D012018	Reflex	An involuntary movement or exercise of function in a part, excited in response to a stimulus applied to the periphery and transmitted to the brain or spinal cord.
D001794	Blood Pressure	PRESSURE of the BLOOD on the ARTERIES and other BLOOD VESSELS.	Systolic Pressure,Diastolic Pressure,Pulse Pressure,Pressure, Blood,Pressure, Diastolic,Pressure, Pulse,Pressure, Systolic,Pressures, Systolic
D002415	Cats	The domestic cat, Felis catus, of the carnivore family FELIDAE, comprising over 30 different breeds. The domestic cat is descended primarily from the wild cat of Africa and extreme southwestern Asia. Though probably present in towns in Palestine as long ago as 7000 years, actual domestication occurred in Egypt about 4000 years ago. (From Walker's Mammals of the World, 6th ed, p801)	Felis catus,Felis domesticus,Domestic Cats,Felis domestica,Felis sylvestris catus,Cat,Cat, Domestic,Cats, Domestic,Domestic Cat
D003000	Clonidine	An imidazoline sympatholytic agent that stimulates ALPHA-2 ADRENERGIC RECEPTORS and central IMIDAZOLINE RECEPTORS. It is commonly used in the management of HYPERTENSION.	Catapres,Catapresan,Catapressan,Chlophazolin,Clofelin,Clofenil,Clonidine Dihydrochloride,Clonidine Hydrochloride,Clonidine Monohydrobromide,Clonidine Monohydrochloride,Clopheline,Dixarit,Gemiton,Hemiton,Isoglaucon,Klofelin,Klofenil,M-5041T,ST-155,Dihydrochloride, Clonidine,Hydrochloride, Clonidine,M 5041T,M5041T,Monohydrobromide, Clonidine,Monohydrochloride, Clonidine,ST 155,ST155