Effect of intraventricular injection of dopamine, norepinephrine, acetylcholine, and 5-hydroxytryptamine on immunoreactive somatostatin release into rat hypophyseal portal blood

Kazuo Chihara, Akira Arimura, Andrew V. Schally

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The effect of several putative neurotransmitters in the regulation of somatostatin release from the median eminence into hypophyseal portal blood was investigated in male rats under urethane anesthesia. Using a specially designed microfraction collector, hypophyseal portal blood was collected at 15-min intervals into five separate tubes containing 2 N acetic acid. Immunoreactive somatostatin (IRS) in the acid-blood mixtures was extracted with acetone, washed with organic solvents, and determined by RIA. Dopamine, norepinephrine, 5-hydroxytryptamine, or acetylcholine in a dose of 108 mol/5μl freshly prepared 5% glucose solution or 5 μl glucose solution alone was injected into the third ventricle immediately after collection of the first blood sample. In 10 control animals, the mean (±SE) secretion rate and concentration of IRS were 3.90 ± 0.66 pg/min and 628 ± 126 pg/ml before injection of 5% glucose, 2.12 ± 0.28 pg/min and 286 ± 22 pg/ml 15 min after the injection, 1.93 ± 0.17 pg/min and 261 ± 18 pg/ml at 30 min, 1.53 ± 0.21 pg/min and 240 ± 14 pg/ml at 45 min, and 2.02 ± 0.31 pg/min and 221 ± 33 pg/ml at 60 min. Portal IRS values increased significantly to 8.87 ± 1.94 pg/min and 1411 ± 166 pg/ml 30 min after dopamine injection, 5.93 ± 0.90 pg/min and 1055 ± 152 pg/ml 15 min after norepinephrine injection, and 5.44 ± 0.90 pg/min and 579 ± 88 pg/ml 45 min after acetylcholine injection. The injection of 5-hydroxytryptamine did not change portal IRS significantly. The stimulatory effect of dopamine on IRS release was also observed in Althesin-anesthetized rats. These results suggest that the secretion of IRS into hypophyseal portal blood is stimulated through the activation of catecholaminergic and cholinergic mechanisms in the rat.

Original languageEnglish (US)
Pages (from-to)1656-1662
Number of pages7
Issue number6
StatePublished - Jun 1979
Externally publishedYes


ASJC Scopus subject areas

  • Endocrinology

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