The hypothalamohypophyseal system in vitro: Electrophysiology of the pars intermedia and evidence for both excitatory and inhibitory inputs

M. Duff Davis, Helmut L. Haas, Walter Lichtensteiger

Research output: Contribution to journalArticle

8 Scopus citations

Abstract

The purpose of this study was to better assess the function of catecholamine-containing nerve terminals in the pituitary pars intermedia lobe. Hypothalamohypophyseal explants, which included the intact mediobasal hypothalamis (MBH), median eminence, infundibular stalk and the neurointermediate lobe, were obtained from 2-3-week-old male and female albino rats. The tissue was placed in a perfusion chamber and maintained under physiological conditions for up to 12 h. A set of bipolar stimulating electrodes was positioned on the surface of the median eminence, infundibular stalk or the rostroventral arcuate nucleus of the MBH. A microelectrode recorded electrical activity in the pars intermedia gland. Two types of spontaneous action potentials were found; fast 2-4 ms duration neural fiber type spikes and slower 7-10 ms duration spikes probably derived from non-neural endocrine cells. Single-pulse electrical stimulation at all 3 sites evoked both kinds of potentials, while trains of stimuli (0.1-20 Hz) decreased or completely inhibited the basal firing rate of the slower ones. Application of the neuroleptic. l-sulpiride (0.01, 0.1 or 1.0 μmol), to the perfusion medium increased the spontaneous endocrine cell activity and blocked the stimulus-induced inhibition in the explants but had no effect on the activity in isolated pituitaries. Dopamine (0.1 μmol), which is knoqn to inhibit the secretion of pro-opiomelanocortin peptides, reversibly suppressed the spontaneous endocrine cell potentials. These observations support a hypothesis for the presence of a functional tuberohypophyseal dopamine inhibitory system and a possible, but as yet unidentifiable, excitatory system in the pars intermedia. Thus, hypothalamohypophyseal explants can be used to elucidate specific information on this type of neuroendocrine axis.

Original languageEnglish (US)
Pages (from-to)97-104
Number of pages8
JournalBrain Research
Volume334
Issue number1
DOIs
StatePublished - May 13 1985

Keywords

  • dopamine
  • electrophysiology
  • explant
  • hypothalamus
  • pars intermedia
  • pituitary

ASJC Scopus subject areas

  • Neuroscience(all)
  • Molecular Biology
  • Clinical Neurology
  • Developmental Biology

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