The biphasic effects of locus coeruleus noradrenergic activation on dendrodendritic inhibition in the rat olfactory bulb

• Published in: Brain research Vol. 783; no. 2; pp. 272 - 279
• Main Authors: Okutani, Fumino, Kaba, Hideto, Takahashi, Seiichi, Seto, Katsuo
• Format: Journal Article
• Language: English
• Published: London Elsevier B.V 09.02.1998; Amsterdam Elsevier; New York, NY
• Subjects: Adrenergic alpha-Antagonists - pharmacology; Adrenergic beta-Agonists - pharmacology; Animals; Biological and medical sciences; Dendrites - physiology; Dendrodendritic synapse; Electric Stimulation; Evoked Potentials; Female; Field potential; Fundamental and applied biological sciences. Psychology; Glutamic Acid - pharmacology; Isoproterenol - pharmacology; Locus Coeruleus - chemistry; Locus Coeruleus - cytology; Locus Coeruleus - physiology; Neural Inhibition - drug effects; Neural Inhibition - physiology; Neurons - drug effects; Neurons - physiology; Neurons - ultrastructure; Noradrenergic input; Norepinephrine - physiology; Olfaction; Olfactory Bulb - cytology; Olfactory Bulb - drug effects; Olfactory Bulb - physiology; Olfactory system and olfaction. Gustatory system and gustation; Paired-pulse inhibition; Phentolamine - pharmacology; Rats; Rats, Wistar; Receptors, Adrenergic - physiology; Smell - physiology; Timolol - pharmacology; Vertebrates: nervous system and sense organs; Noradrenergic input; Field potential; Paired-pulse inhibition; Dendrodendritic synapse; Olfaction; Rat; Electrical stimulus; Rodentia; Central nervous system; Catecholamine; Vertebrata; Mammalia; Olfactory pathway; Paired stimulation; Olfactory bulb; Norepinephrine; Adrenergic receptor; Locus coeruleus; Brain (vertebrata)
• ISSN: 0006-8993; 1872-6240
• DOI: 10.1016/S0006-8993(97)01371-1

Some forms of olfactory learning require intact noradrenergic terminals in the olfactory bulb that originate from the locus coeruleus. To clarify the action of noradrenergic inputs on the dendrodendritic interaction between mitral and granule cells in the rat olfactory bulb, we analyzed field potentials in the granule cell layer of the olfactory bulb evoked by paired-pulse stimulation of the lateral olfactory tract before and after the activation of the locus coeruleus. Locus coeruleus activation by glutamate injection in the vicinity of the nucleus changed only the test response without any effect on conditioning response. Paired-pulse inhibition measured from the ratio of test response amplitude to conditioning response amplitude was significantly depressed immediately after locus coeruleus activation. Conversely, 2 min later, paired-pulse inhibition was significantly potentiated. The significant potentiation of inhibition lasted for several minutes. The depression–potentiation sequence of paired-pulse inhibition was blocked by infusion of timolol, a β-antagonist, into the olfactory bulb, in a dose-dependent manner, but not by infusion of phentolamine, an α-antagonist. Infusion of isoproterenol, a β-agonist, into the bulb mimicked the depression of paired-pulse inhibition by locus coeruleus activation. These results suggest that glutamate activation of the locus coeruleus produces a depression–potentiation sequence in granule cell-mediated feedback inhibition onto mitral cells in the olfactory bulb through β-adrenergic receptors.