TY - JOUR
T1 - The hypothalamohypophyseal system in vitro
T2 - Electrophysiology of the pars intermedia and evidence for both excitatory and inhibitory inputs
AU - Duff Davis, M.
AU - Haas, Helmut L.
AU - Lichtensteiger, Walter
PY - 1985/5/13
Y1 - 1985/5/13
N2 - 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.
AB - 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.
KW - dopamine
KW - electrophysiology
KW - explant
KW - hypothalamus
KW - pars intermedia
KW - pituitary
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U2 - 10.1016/0006-8993(85)90571-2
DO - 10.1016/0006-8993(85)90571-2
M3 - Article
C2 - 2986782
AN - SCOPUS:0021989164
VL - 334
SP - 97
EP - 104
JO - Brain Research
JF - Brain Research
SN - 0006-8993
IS - 1
ER -