MCH-containing neurons in the hypothalamus of the cat: searching for a role in the control of sleep and wakefulness.
Neurons that utilize melanin-concentrating hormone (MCH) and others that employ hypocretin as neurotransmitter are located in the hypothalamus and project diffusely throughout the CNS, including areas that participate in the generation and maintenance of the states of sleep and wakefulness. In the present report, immunohistochemical methods were employed to examine the distribution of MCHergic and hypocretinergic neurons. In order to test the hypothesis that the MCHergic system is capable of influencing specific behavioral states, we studied Fos immunoreactivity in MCH-containing neurons during (1) quiet wakefulness, (2) active wakefulness with motor activity, (3) active wakefulness without motor activity, (4) quiet sleep and (5) active sleep induced by carbachol (AS-carbachol). We determined that MCHergic neuronal somata in the cat are intermingled with hypocretinergic neurons in the dorsal and lateral hypothalamus, principally in the tuberal and tuberomammillary regions; however, hypocretinergic neurons extended more in the anterior-posterior axis than MCHergic neurons. Axosomatic and axodendritic contacts were common between these neurons. In contrast to hypocretinergic neurons, which are known to be active during motor activity and AS-carbachol, Fos immunoreactivity was not observed in MCH-containing neurons in conjunction with any of the preceding behavioral conditions. Non-MCHergic, non-hypocretinergic neurons that expressed c-fos during active wakefulness with motor activity were intermingled with MCH and hypocretin-containing neurons, suggesting that these neurons are related to some aspect of motor function. Further studies are required to elucidate the functional sequela of the interactions between MCHergic and hypocretinergic neurons and the phenotype of the other neurons that were active during motor activity.
Torterolo
Pablo
P
Departamento de Fisiología, Facultad de Medicina, Universidad de la República, General Flores 2125, 11800, Montevideo, Uruguay.
Sampogna
Sharon
S
Morales
Francisco R
FR
Chase
Michael H
MH
D000109:Acetylcholine / Q000378:metabolism; D000818:Animals; D002217:Carbachol / Q000494:pharmacology; D002415:Cats; D018679:Cholinergic Agonists / Q000494:pharmacology; D007028:Hypothalamic Hormones / Q000378:metabolism*; D007031:Hypothalamus / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D007150:Immunohistochemistry; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D008543:Melanins / Q000378:metabolism*; D009043:Motor Activity / Q000187:drug effects / Q000502:physiology; D009068:Movement / Q000187:drug effects / Q000502:physiology; D009434:Neural Pathways / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D009479:Neuropeptides / Q000378:metabolism; D000068797:Orexins; D010907:Pituitary Hormones / Q000378:metabolism*; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D012890:Sleep / Q000187:drug effects / Q000502:physiology*; D012895:Sleep, REM / Q000187:drug effects / Q000502:physiology; D013569:Synapses / Q000378:metabolism / Q000648:ultrastructure; D014851:Wakefulness / Q000187:drug effects / Q000502:physiology*
D018679:Cholinergic Agonists; D007028:Hypothalamic Hormones; D047908:Intracellular Signaling Peptides and Proteins; D008543:Melanins; D009479:Neuropeptides; D000068797:Orexins; D010907:Pituitary Hormones; D016760:Proto-Oncogene Proteins c-fos; C019463:melanin-concentrating hormone; D002217:Carbachol; D000109:Acetylcholine