Identification of mechanisms involved in the modulation of release of noradrenaline in the hippocampus of the rabbit in vitro.
The modulation of the electrically-evoked release of noradrenaline by various possible neurotransmitters or neuromodulators in the hippocampus was studied in the dorsal part of the hippocampus of the rabbit. Slices of this tissue were preincubated with [3H]noradrenaline and superfused with a medium containing 30 microM cocaine. The evoked overflow of tritium was calcium-dependent, tetrodotoxin-sensitive and subject to modulation by presynaptic alpha 2-autoreceptors. Drugs with affinity for beta-adrenoceptors (up to 1 microM), muscarinic (up to 10 microM), nicotinic (up to 100 microM), GABA- (up to 1000 microM), glutamate- (up to 100 microM) and prostaglandin-receptors (up to 1 microM) did not show any modulatory influence on the evoked release of noradrenaline. In contrast, morphine (1 microM) and fentanyl (1 microM) significantly reduced the evoked overflow; this effect was antagonized by naloxone (10 microM), which, given alone, was ineffective. Apomorphine (1 microM) reduced the release of noradrenaline in the absence, and increased it in the presence, of 0.1 microM haloperidol; haloperidol (0.1 microM), given alone was ineffective. From these results it is concluded that, in addition to the well-known alpha 2-autoreceptor mechanism, presynaptic opiate-, D2- and probably D1-receptors might modulate the release of noradrenaline in the hippocampus.
D000818:Animals; D004558:Electric Stimulation; D005971:Glutamates / Q000494:pharmacology; D018698:Glutamic Acid; D006624:Hippocampus / Q000378:metabolism*; D066298:In Vitro Techniques; D009411:Nerve Endings / Q000378:metabolism; D009638:Norepinephrine / Q000378:metabolism*; D010275:Parasympathetic Nervous System / Q000502:physiology; D011453:Prostaglandins / Q000494:pharmacology; D011817:Rabbits; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects; D011943:Receptors, Adrenergic, beta / Q000187:drug effects; D011954:Receptors, Dopamine / Q000187:drug effects; D011963:Receptors, GABA-A / Q000187:drug effects; D011978:Receptors, Nicotinic / Q000187:drug effects; D011957:Receptors, Opioid / Q000187:drug effects; D011982:Receptors, Prostaglandin / Q000187:drug effects; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology
D005971:Glutamates; D011453:Prostaglandins; D011942:Receptors, Adrenergic, alpha; D011943:Receptors, Adrenergic, beta; D011954:Receptors, Dopamine; D011963:Receptors, GABA-A; D011978:Receptors, Nicotinic; D011957:Receptors, Opioid; D011982:Receptors, Prostaglandin; D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid; D009638:Norepinephrine