Biomaterial Database

Inhibition by 5,6-dihydroxy-2-dimethylaminotetralin (M7) of noradrenergic neurotransmission in the rabbit hypothalamus: role of alpha-2 adrenoceptors and of dopamine receptors. 1985

A M Galzin, and S Z Langer

Rabbit hypothalamic slices were prelabeled with [3H]norepinephrine and transmitter release elicited by electrical stimulation. In the presence of 10 microM cocaine and in a low Ca++ medium (0.65 mM), exposure for 8 min to exogenous dopamine (0.01-1 microM) inhibited, in a concentration-dependent manner, the electrically evoked release of [3H]norepinephrine. This inhibitory effect of dopamine on [3H]norepinephrine release was antagonized by the dopamine receptor antagonist S-sulpiride (1 microM), but remained unchanged in the presence of the alpha-2 adrenoceptor antagonists idazoxan (1 microM) or yohimbine (0.1 microM). These results indicate that, in a low Ca++ medium, exposure to dopamine decreased [3H]norepinephrine overflow in rabbit hypothalamic slices through the exclusive activation of presynaptic inhibitory dopamine receptors. M7 (5,6-dihydroxy-2-dimethylaminotetralin) is a potent agonist at central presynaptic dopamine autoreceptors and at peripheral alpha-2 adrenoceptors. Exposure to M7 in a normal Ca++ medium, inhibited in a concentration-dependent manner the electrically evoked release of [3H]norepinephrine without affecting the spontaneous outflow of radioactivity. The slope of the concentration-effect curve for these inhibitory effects of M7 was rather flat and the maximal inhibition obtained was 80%. The selective D2 receptor antagonist S-sulpiride (1 microM) failed to produce a significant shift to the right in the concentration-effect curve for the inhibitory effects of M7 on [3H]norepinephrine release. The preferential alpha-2 adrenoceptor antagonist yohimbine (0.1 microM) significantly antagonized the inhibition of [3H]norepinephrine release elicited by 0.01 microM M7, but not for higher concentrations of this aminotetraline.(ABSTRACT TRUNCATED AT 250 WORDS)

UI	MeSH Term	Description	Entries
D007031	Hypothalamus	Ventral part of the DIENCEPHALON extending from the region of the OPTIC CHIASM to the caudal border of the MAMMILLARY BODIES and forming the inferior and lateral walls of the THIRD VENTRICLE.	Lamina Terminalis,Preoptico-Hypothalamic Area,Area, Preoptico-Hypothalamic,Areas, Preoptico-Hypothalamic,Preoptico Hypothalamic Area,Preoptico-Hypothalamic Areas
D009284	Naphthols	Naphthalene derivatives carrying one or more hydroxyl (-OH) groups at any ring position. They are often used in dyes and pigments, as antioxidants for rubber, fats, and oils, as insecticides, in pharmaceuticals, and in numerous other applications.	Hydroxynaphthalene,Hydroxynaphthalenes,Naphthol
D009435	Synaptic Transmission	The communication from a NEURON to a target (neuron, muscle, or secretory cell) across a SYNAPSE. In chemical synaptic transmission, the presynaptic neuron releases a NEUROTRANSMITTER that diffuses across the synaptic cleft and binds to specific synaptic receptors, activating them. The activated receptors modulate specific ion channels and/or second-messenger systems in the postsynaptic cell. In electrical synaptic transmission, electrical signals are communicated as an ionic current flow across ELECTRICAL SYNAPSES.	Neural Transmission,Neurotransmission,Transmission, Neural,Transmission, Synaptic
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
D011817	Rabbits	A burrowing plant-eating mammal with hind limbs that are longer than its fore limbs. It belongs to the family Leporidae of the order Lagomorpha, and in contrast to hares, possesses 22 instead of 24 pairs of chromosomes.	Belgian Hare,New Zealand Rabbit,New Zealand Rabbits,New Zealand White Rabbit,Rabbit,Rabbit, Domestic,Chinchilla Rabbits,NZW Rabbits,New Zealand White Rabbits,Oryctolagus cuniculus,Chinchilla Rabbit,Domestic Rabbit,Domestic Rabbits,Hare, Belgian,NZW Rabbit,Rabbit, Chinchilla,Rabbit, NZW,Rabbit, New Zealand,Rabbits, Chinchilla,Rabbits, Domestic,Rabbits, NZW,Rabbits, New Zealand,Zealand Rabbit, New,Zealand Rabbits, New,cuniculus, Oryctolagus
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
D011954	Receptors, Dopamine	Cell-surface proteins that bind dopamine with high affinity and trigger intracellular changes influencing the behavior of cells.	Dopamine Receptors,Dopamine Receptor,Receptor, Dopamine
D004146	Dioxanes	Compounds that contain the structure 1,4-dioxane.
D004298	Dopamine	One of the catecholamine NEUROTRANSMITTERS in the brain. It is derived from TYROSINE and is the precursor to NOREPINEPHRINE and EPINEPHRINE. Dopamine is a major transmitter in the extrapyramidal system of the brain, and important in regulating movement. A family of receptors (RECEPTORS, DOPAMINE) mediate its action.	Hydroxytyramine,3,4-Dihydroxyphenethylamine,4-(2-Aminoethyl)-1,2-benzenediol,Dopamine Hydrochloride,Intropin,3,4 Dihydroxyphenethylamine,Hydrochloride, Dopamine
D004357	Drug Synergism	The action of a drug in promoting or enhancing the effectiveness of another drug.	Drug Potentiation,Drug Augmentation,Augmentation, Drug,Augmentations, Drug,Drug Augmentations,Drug Potentiations,Drug Synergisms,Potentiation, Drug,Potentiations, Drug,Synergism, Drug,Synergisms, Drug