Effects of hypothalamic paraventricular nucleus lesion on the cold-stimulated TSH responses to 5-HT in male rats.
The effects of lesion of the hypothalamic paraventricular nuclei (PVNx), the main thyrotrophic area, on the cold-stimulated thyrotropin (TSH) responses to intracerebroventricular (i.c.v.) 5-HT were studied in male rats. PVNx significantly attentuated the cold-stimulated TSH levels, but significantly affected neither hypothalamic thyrotropin-releasing hormone nor somatostatin content. Serum T3 levels were significantly decreased 8 days after PVNx. Irrespective of the lesion (sham or PVNx), 5-HT infusion (9 micrograms per rat) into the posterior third ventricle attenuated markedly the cold-stimulated TSH levels, whereas infusion into the anterior third ventricle did not. Bilateral 5-HT infusions (2 micrograms per side) into the hypothalamic dorsomedial nuclei significantly decreased serum TSH, but bilateral infusions into the posterior hypothalamic nuclei were without effect. Sham-lesion and PVNx decreased serum prolactin levels without affecting the stimulation of prolactin secretion by i.c.v. 5-HT. These results suggest that the inhibitory effect of i.c.v. 5-HT on TSH secretion and its stimulatory action on prolactin secretion are only partially dependent on the PVN.
Toivonen
M
M
Research Unit of Neurobiology, University of Helsinki, Finland.
Tuomainen
P
P
Männistö
P T
PT
D000818:Animals; D001831:Body Temperature; D003080:Cold Temperature; D004298:Dopamine / Q000378:metabolism; D007031:Hypothalamus / Q000378:metabolism; D008297:Male; D010286:Paraventricular Hypothalamic Nucleus / Q000502:physiology*; D011388:Prolactin / Q000097:blood; D051381:Rats; D011919:Rats, Inbred Strains; D012007:Rectum; D012701:Serotonin / Q000494:pharmacology*; D012964:Sodium / Q000378:metabolism; D013004:Somatostatin / Q000378:metabolism; D013963:Thyroid Hormones / Q000097:blood; D013972:Thyrotropin / Q000097:blood / Q000378:metabolism*; D013973:Thyrotropin-Releasing Hormone / Q000378:metabolism
D013963:Thyroid Hormones; D012701:Serotonin; D013004:Somatostatin; D013973:Thyrotropin-Releasing Hormone; D011388:Prolactin; D013972:Thyrotropin; D012964:Sodium; D004298:Dopamine