CCK-8 excites oxytocin-secreting neurons in the paraventricular nucleus in rats--possible involvement of noradrenergic pathway.
Systemic administration of CCK-8 increased plasma oxytocin (OXT) level in rats anesthetized with a mixture of urethane and alpha-chloralose. Extracellular recordings were made from magnocellular neurosecretory neurons in the paraventricular nucleus (PVN) of the hypothalamus in anesthetized rats to examine the effects of CCK-8 on the firing of PVN neurons. Thirteen out of 16 nonphasic neurons (putative OXT-secreting neurons) were excited by intravenous and/or intraperitoneal administration of CCK-8. By contrast, 8 out of 10 phasic cells, vasopressin(AVP)-secreting cells, were inhibited by systemic administration of CCK-8. Four out of five nonneurosecretory neurons in the PVN were excited by the administration of CCK-8. Moreover, microiontophoretically applied phentolamine blocked the excitatory responses induced by CCK-8 in nonphasic neurons. We measured extracellular noradrenaline (NA) level in the PVN, using in vivo microdialysis. Intravenous administration of CCK-8 induced NA release in the PVN. These results suggest that CCK-8 activates the excitatory afferent pathway to putative OXT-secreting neurons in the PVN which may, at least in part, be involved in the central noradrenergic projection.
Ueta
Y
Y
Department of Physiology, School of Medicine, University of Occupational and Environmental Health, Kitakyushu, Japan.
Kannan
H
H
Higuchi
T
T
Negoro
H
H
Yamashita
H
H
D018674:Adrenergic Antagonists; D000818:Animals; D007478:Iontophoresis; D008297:Male; D017551:Microdialysis; D009474:Neurons / Q000187:drug effects*; D009638:Norepinephrine / Q000502:physiology*; D010121:Oxytocin / Q000378:metabolism*; D010286:Paraventricular Hypothalamic Nucleus / Q000187:drug effects* / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D012844:Sincalide / Q000494:pharmacology*
D018674:Adrenergic Antagonists; D010121:Oxytocin; D012844:Sincalide; D009638:Norepinephrine