Histaminergic regulation of prolactin secretion: involvement of serotoninergic neurons.
The possible involvement of the serotoninergic system in histamine-induced PRL secretion was studied in urethane anesthetized male rats. Intracerebroventricular infusion of histamine (30 micrograms) stimulated PRL secretion 10-fold. This effect was mimicked by the H2-receptor agonist dimaprit (300 micrograms), while the H1-receptor agonist 2-thiazolylethylamine (140 micrograms) had no effect. Pretreatment with the serotonin receptor blockers methysergide (2.5 mg/kg i.p.) or ketanserin (2.5 or 10.0 mg/kg i.p.) reduced the PRL peak response to histamine 75, 54, or 58%, respectively. During serotonin receptor blockade, dimaprit had a stimulatory effect similar to that of histamine, while 2-thiazolylethylamine had no effect. Intraarterial infusion of histamine (420 micrograms) stimulated PRL secretion 6-fold. This effect was mimicked by the H1-receptor agonist 2-thiazolylethylamine (1,900 micrograms), while the H2-receptor agonist dimaprit (3,000 micrograms) had no effect. Pretreatment with methysergide (2.5 mg/kg i.p.) or ketanserin (2.5 or 10.0 mg/kg i.p.) reduced the peak response to histamine 54, 54, or 51% respectively. The effect of histamine was mimicked by 2-thiazolylethylamine, while dimaprit slightly inhibited the PRL secretion. The antiserotoninergic activity of methysergide and ketanserin was demonstrated by their ability to prevent the PRL-releasing effect to serotonin. The effects of methysergide and ketanserin were not due to dopamine-like activity, since none of the drugs affected basal PRL secretion and since the dopamine receptor antagonist pimozide did not prevent the inhibitory effect of methysergide on the histamine-induced PRL release. The findings indicate that histamine-stimulated PRL secretion is mediated in part by serotoninergic neurons.
Knigge
U
U
Institute of Medical Physiology C, Panum Institute, University of Copenhagen, Denmark.
Sleimann
I
I
Matzen
S
S
Warberg
J
J
D017259:Dimaprit; D006632:Histamine / Q000008:administration & dosage*; D007650:Ketanserin / Q000008:administration & dosage; D008784:Methysergide / Q000008:administration & dosage; D009474:Neurons / Q000502:physiology; D011388:Prolactin / Q000097:blood* / Q000378:metabolism; D011954:Receptors, Dopamine / Q000187:drug effects / Q000502:physiology; D011985:Receptors, Serotonin / Q000187:drug effects* / Q000502:physiology; D012701:Serotonin / Q000008:administration & dosage; D013890:Thiourea / Q000008:administration & dosage
D011954:Receptors, Dopamine; D011985:Receptors, Serotonin; D012701:Serotonin; D006632:Histamine; D011388:Prolactin; D007650:Ketanserin; D013890:Thiourea; D008784:Methysergide; D017259:Dimaprit