Abstract
Brain serotonergic neurons display a distinctive slow and regular discharge pattern in behaving animals. This activity gradually declines across the arousal-waking sleep cycle, becoming virtually silent during rapid eye movement sleep. The activity of these neurons, in both the pontine and medullary groups, is generally unresponsive to a variety of physiological challenges or stressors. However, these neurons are activated in association with increased muscle tone/tonic motor activity, especially if the motor activity is in the repetitive or central pattern generator mode. We interpret these data within the following theoretical framework. The primary function of the brain serotonergic system is to facilitate motor output. Concurrently, the system coordinates autonomic and neuroendocrine function with the present motor demand, and inhibits information processing in various sensory pathways. Reciprocally, when the serotonin system is briefly inactivated (e.g., during orientation to salient stimuli), this disfacilitates motor function and disinhibits sensory information processing. It is within this context that serotonin exerts its well-known effects on pain, feeding, memory, mood, etc.
Similar content being viewed by others
Log in or create a free account to read this content
Gain free access to this article, as well as selected content from this journal and more on nature.com
or
References
Allen GV, Cechetto DF . (1994): Serotoninergic and nonserotoninergic neurons in the medullary raphe system have axon collateral projections to autonomic and somatic cell groups in the medulla and spinal cord. J Comp Neurol 350: 357–366
Auerbach S, Fornal C, Jacobs BL . (1985): Response of serotonin-containing neurons in nucleus raphe magnus to morphine, noxious stimuli, and periaqueductal gray stimulation in freely moving cats. Exp Neurol 88: 609–628
Fornal CA, Litto WJ, Morilak DA, Jacobs BL . (1987): Single-unit responses of serotonergic dorsal raphe nucleus neurons to environmental heating and pyrogen administration in freely moving cats. Exp Neurol 98: 388–403
Fornal CA, Litto WJ, Morilak DA, Jacobs BL . (1989): Single-unit responses of serotonergic neurons to glucose and insulin administration in behaving cats. Am J Physiol 257: R1345–R1353
Fornal CA, Litto WJ, Morilak DA, Jacobs BL . (1990): Single-unit responses of serotonergic dorsal raphe neurons to vasoactive drug administration in freely moving cats. Am J Physiol 259: R963–R972
Fornal CA, Metzler CW, Marrosu F, Ribiero-do-Valle LE, Jacobs BL . (1996): A subgroup of dorsal raphe serotonergic neurons in the cat is strongly activated during oral-buccal movements. Brain Res 716: 123–133
Gao K, Chen DO, Genzen JR, Mason P . (1998): Activation of serotonergic neurons in the raphe magnus is not necessary for morphine analgesia. J Neurosci 18: 1860–1868
Jacobs BL, Fornal CA . (1991): Activity of brain serotonergic neurons in the behaving animal. Pharmacol Rev 43: 563–578
Jacobs BL, Azmitia EC . (1992): Structure and function of the brain serotonin system. Physiol Rev 72: 165–229
Jacobs BL, Fornal CA . (1995): Activation of 5-HT neuronal activity during motor behavior. Semin Neurosci 7: 401–408
Jacobs BL, MartÃn FJ, Fornal CA, Metzler CW . (1997): Systemic administration of insulin decreases the activity of medullary serotonergic neurons in awake cats. Soc Neurosci Abstr 23: 1227
Jouvet M, Delorme F . (1965): Locus coeruleus et sommeil paradoxal. C R Soc Biol 159: 895–899
Levine ES, Jacobs BL . (1992): Neurochemical afferents controlling the activity of serotonergic neurons in the dorsal raphe nucleus: Microiontophoretic studies in the awake cat. J Neurosci 12: 4037–4044
MartÃn FJ, Gallegos RA, Fornal CA, Metzler CW, Jacobs BL . (1997): Effect of environmental cooling on the activity of pontine and medullary serotonergic neurons in awake cats. Soc Neurosci Abstr 23: 1226
MartÃn FJ, Fornal CA, Metzler CW, Jacobs BL . (1998): The activity of medullary serotonergic neurons in freely moving cats is unaffected by cardiovascular manipulations that evoke reflex changes in autonomic outflow. Soc Neurosci Abstr 24: 1106
Nitz D, Siegel J . (1997): GABA release in the dorsal raphe nucleus: Role in the control of REM sleep. Am J Physiol 273: R451–R455
Potrebic SB, Field HL, Mason P . (1994): Serotonin immunoreactivity is contained in one physiological cell class in the rat rostral ventromedial medulla. J Neurosci 14: 1655–1665
Rueter LE, Jacobs BL . (1996): A microdialysis examination of serotonin release in the rat forebrain induced by behavioral/environmental manipulations. Brain Res 739: 57–69
Skagerberg G, Bjorklund A . (1985): Topographic principles in the spinal projections of serotonergic and non-serotonergic brainstem neurons in the rat. Neurosci 15: 445–480
Steinbusch HWM . (1981): Distribution of serotonin-immunoreactivity in the central nervous system of the rat–Cell bodies and terminals. Neuroscience 4: 557–618
Steinfels GF, Heym J, Strecker RE, Jacobs BL . (1983): Raphe unit activity in freely moving cats is altered by manipulations of central but not peripheral motor systems. Brain Res 279: 77–84
Trulson ME, Jacobs BL, Morrison AR . (1981): Raphe unit activity during REM sleep in normal cats and in pontine lesioned cats displaying REM sleep without atonia. Brain Res 226: 75–91
Veasey SC, Fornal CA, Metzler CW, Jacobs BL . (1995): Response of serotonergic caudal raphe neurons in relation to specific motor activities in freely moving cats. J Neurosci 15: 5346–5359
Veasey SC, Fornal CA, Metzler CW, Jacobs BL . (1997): Single-unit responses of serotonergic dorsal raphe neurons to specific motor challenges in freely moving cats. Neuroscience 79: 161–169
Wilkinson LO, Auerbach SB, Jacobs BL . (1991): Extracellular serotonin levels change with behavioral state but not pyrogen-induced hyperthermia. J Neurosci 11: 2732–2741
Wilkinson LO, Jacobs BL . (1988): Lack of response of serotonergic neurons in the dorsal raphe nucleus of freely moving cats to stressful stimuli. Exp Neurol 101: 445–457
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Jacobs, B., Fornal, C. Activity of Serotonergic Neurons in Behaving Animals. Neuropsychopharmacol 21 (Suppl 1), 9–15 (1999). https://doi.org/10.1016/S0893-133X(99)00012-3
Received:
Revised:
Accepted:
Issue date:
DOI: https://doi.org/10.1016/S0893-133X(99)00012-3
Keywords
This article is cited by
-
Reward probability and timing uncertainty alter the effect of dorsal raphe serotonin neurons on patience
Nature Communications (2018)
-
The Role of 5-HT1A Receptors in Long-Term Adaptation of Newborn Rats to Hypoxia
Bulletin of Experimental Biology and Medicine (2016)
-
Ascending serotonin neuron diversity under two umbrellas
Brain Structure and Function (2016)
