Catecholamine Involvement in Episodic Luteinizing Hormone Release in Adult Ovariectomized Rats12
- 1 September 1976
- journal article
- research article
- Published by The Endocrine Society in Endocrinology
- Vol. 99 (3), 651-658
- https://doi.org/10.1210/endo-99-3-651
Abstract
This study was intended to examine the role of hypothalamic norepinephrine (HNE) and dopamine (HDA) in episodic luteinizing hormone (LH) release in adult ovariectomized rats. Unrestrained, unanesthetized rats with indwelling right atrial cannulae were bled continuously (30, 50 or 100 .mu.l of whole blood/4-6 min for 3-4 h), and the blood samples were analyzed for LH by radioimmunoassay. In other individual rats, changes in the hypothalamic levels of norepinephrine and dopamine after drug administration were determined by a radioisotopic-enzymatic catechol-O-methyl transferase assay. .alpha.-Methyl-p- tyrosine significantly decreased HNE and HDA concentrations but failed to alter episodic LH release. Two dopamine-.beta.-hydroxylase inhibitors (U-14,624 [1-phenyl-3-(.alpha.-thiazolyl)-2-thiourea] and FLA-63 [bis(4-methyl-1-homo-piperanzinyl thiocarbonyl) disulfide]) caused marked reductions in HNE, small but not statistically significant increases in HDA and an inhibition of episodic LH secretion. Apomorphine, a dopamine receptor stimulator, caused a transient (50-60 min) but marked inhibition of episodic LH release. Saline injection had no effect. Pimozide, a blocker of dopamine receptors, prevented the inhibitory effects seen following apomorphine. Although not studied in detail, pimozide alone did not appear to alter episodic LH secretion. In adult ovariectomized rats norepinephrine may be an excitatory neurotransmitter in the modulation of episodic LH release. The activation of dopamine receptors may be capable of inhibiting this release process. However, the apparent inability of pimozide alone to alter episodic LH discharge suggests that under physiological conditions dopamine may not play a role in the modulation of episodic LH secretion.Keywords
This publication has 5 references indexed in Scilit:
- DIFFERENTIAL EFFECTS OF HYPOTHALAMIC DEAFFERENTATION UPON LUTEINIZING HORMONERELEASING HORMONE IN THE MEDIAN EMINENCE AND ORGANUM VASCULOSUM OF THE LAMINA TERMINALISEndocrinology, 1975
- Mode of action of apomorphine and dexamphetamine on gnawing compulsion in ratsPsychopharmacology, 1967
- Suppression of Ovarian Activity in Immature Rats by SerotoninEndocrinology, 1965
- The Mechanism by Which Dibenamine Blocks Pituitary Activation in the Rabbit and RatExperimental Biology and Medicine, 1949
- INHIBITION OF OVULATION IN THE RABBIT BY THE ADRENERGIC-BLOCKING AGENT DIBENAMINEEndocrinology, 1947