Serotonergic raphe neuron

Figure 22.1 Pathways projecting to and from the suprachiasmatic nucleus (SCN). Inputs from photoreceptors in the retina help to reset the circadian clock in response to changes in the light cycle. Other inputs derive from the lateral geniculate complex and the serotonergic, Raphe nuclei and help to reset the SCN in response to non-photic stimuli. Neurons in the SCN project to the hypothalamus, which has a key role in the regulation of the reproductive cycle, mood and the sleep-waking cycle. These neurons also project to the pineal gland which shows rhythmic changes in the rate of synthesis and release of the hormone, melatonin...

Sakai, K. Crochet, S. (2000). Serotonergic dorsal raphe neurons cease firing by disfacilitation during paradoxical sleep. Neuroreport 11, 3237-41. 

The fact that most serotonergic dorsal raphe neurons are dependent on extrinsic excitatory or facilitatory inputs to express their characteristic spontaneous activity may seem to contradict previous studies suggesting that these neurons may function as autonomous pacemakers (42) with an endogenous rhythm (31) attributable to the presence of pacemaker potentials (8). Such a contradiction exists only if one insists that endogenous rhythms and pacemaker potentials must, by definition, be totally autonomous, i.e., completely independent of all extrinsic synaptic or neurohumoral influences. Such a definition would seem too restrictive in view of the fact that some invertebrate neurons display pacemaker potentials only when certain afferent fibers are stimulated (38) or when exposed to certain neurohumoral substances (18,28). 

Serotonergic dorsal raphe neurons basic properties, 171-175 identification of, 171-172 current-voltage relationships in, 177 and LSD, 175-178 noradrenergic activations of, 175... 

LSD and Serotonergic Dorsal Raphe Neurons Intracellular Studies In Vivo and In Vitro George K. Aghajanian... 

BASIC PROPERTIES OF SEROTONERGIC DORSAL RAPHE NEURONS... 

LSD AND SEROTONERGIC DORSAL RAPHE NEURONS LSD and Serotonin Autoreceptors... 

Aghajanian, G. K... and VanderMaelen, C. P. (1982) Intracellular recordings from serotonergic dorsal raphe neurons Pacemaker potentials and the effect of LSD. Brain Res., 238 463-469. 

These results provided support for the hypothesis that the effect of hallucinogenic drugs is mediated by a direct action on serotonergic neurons, possibly one mediated by serotonin receptors. This is consistent with data indicating that raphe neurons receive inputs from other raphe neurons and thus, presumably, contain serotonin receptors on their somata and/or dendrites (65). 

Vandermaelen CP, Aghajanian GK. (1983). Electrophysiological and pharmacological characterization of serotonergic dorsal raphe neurons recorded extracellularly and intracellularly in rat brain slices. Brain Res. 289(1-2) 109-19. 

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