PubMed Health⌕ Search
Home/Archive/PubMed

PubMed · 1593929

Neurotensin-induced activation of hypothalamic dopaminergic neurons is accompanied by a decrease in pituitary secretion of prolactin and alpha-melanocyte-stimulating hormone.

J T Pan·Y Tian·K J Lookingland·K E Moore
View original source ↗Export metadata ↓

Abstract

The effects of neurotensin on the activity of hypothalamic tuberoinfundibular and periventricular-hypophysial dopaminergic (DA) neurons, and on the secretion of pituitary hormones that are tonically regulated by these neurons (i.e. prolactin and alpha-melanocyte-stimulating hormone [alpha MSH], respectively) were examined in estrogen-primed ovariectomized rats. The activity of tuberoinfundibular and periventricular-hypophysial DA neurons was estimated by measuring concentrations of the dopamine metabolite 3,4-dihydroxyphenylacetic acid (DOPAC) in the terminals of these neurons in the median eminence and intermediate lobe of the posterior pituitary, respectively. Intracerebroventricular administration of neurotensin caused a dose- and time-related increase in DOPAC concentrations in both the median eminence and intermediate lobe, and a concurrent decrease in plasma levels of prolactin and alpha MSH. These results suggest that neurotensin-induced inhibition of secretion of prolactin and alpha MSH from the pituitary may be due to the stimulatory action of this neuropeptide on the release of dopamine from tuberoinfundibular and periventricular-hypophysial neurons.

Explore related subjects

3,4-Dihydroxyphenylacetic AcidAnimalsDopamineDose-Response Relationship, DrugFemaleInjections, IntraventricularMedian EminenceMelanocyte-Stimulating HormonesNeuronsNeurotensinPituitary Gland, PosteriorProlactinRatsJournal ArticleResearch Support, U.S. Gov't, P.H.S.

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

J T Pan, Y Tian, K J Lookingland, K E Moore. 1992. Neurotensin-induced activation of hypothalamic dopaminergic neurons is accompanied by a decrease in pituitary secretion of prolactin and alpha-melanocyte-stimulating hormone.. https://doi.org/10.1016/0024-3205(92)90531-s

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related citations

PubMed1992

A cholinergic input to the substantia nigra pars compacta increases striatal dopamine metabolism measured by in vivo voltammetry.

3,4-Dihydroxyphenylacetic acid (DOPAC) and ascorbic acid (AA) were measured by differential pulse voltammetry in the neostriatum of anesthetized rats. Physostigmine (2.3 nmol) applied into the substantia nigra pars compacta (SNc), increased DOPAC concentration in the ipsilateral neostriatum, but did not modify AA levels. The largest increase of striatal DOPAC (37 +/- 8% above basal) was observed when physostigmine was applied at less than 0.5 mm from SNc, and decreased with increasing distance of the injection site from the pars compacta region. Chemical stimulation of the pedunculopontine tegmental nucleus (PPN) with kainic acid (2.3 nmol) increased both DOPAC and AA concentration in the ipsilateral neostriatum. Pretreatment with the muscarinic antagonist scopolamine (5 mg/kg, i.p.) inhibited the increase of striatal DOPAC from 20 to 70 min after kainic acid injection into the PPN, whereas the increase of AA was reduced from 90 to 160 min. By contrast, the nicotinic antagonist mecamylamine (4 mg/kg, i.p.) did not inhibit neither DOPAC nor AA increase elicited by the chemical stimulation of PPN. These results support the existence of cholinergic neurotransmission within the SNc that increases the firing rate of nigrostriatal dopaminergic neurons, enhancing dopamine turnover in neostriatum without changes in AA release. They also suggest that the PPN could be the origin of cholinergic afferents to the SNc that modulate the activity of dopaminergic neurons, through activation of muscarinic cholinergic receptors. Finally, the activation of a multisynaptic loop involving a cholinergic pathway which modulates the activity of the glutamatergic corticostriatal neurons is postulated to explain the increase of AA in neostriatum observed after PPN stimulation.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1992

Sexual differences in the stimulatory effects of bombesin on tuberoinfundibular dopaminergic neurons.

The purpose of this study was to (1) examine the effects of central administration of bombesin on the activity of tuberoinfundibular dopaminergic (DA) neurons in male and female rats, and (2) determine if sexual differences in the responsiveness of these neurons to bombesin were due to the presence of prolactin or gonadal steroids. The activity of tuberoinfundibular DA neurons was estimated by measuring the concentrations of the dopamine metabolite 3,4-dihydroxyphenylacetic acid (DOPAC) in terminals of these neurons in the median eminence. The effects of bombesin on the secretion of prolactin and alpha-melanocyte stimulating hormone (alpha MSH), and the activities of nigrostriatal, mesolimbic, and periventricular-hypophysial DA neurons were also determined in gonadally intact male and female rats. Central administration of bombesin (10 ng/rat; i.c.v.) decreased prolactin secretion in gonadally intact male and female rats, but only in males was this associated with an increase in the activity of tuberoinfundibular DA neurons. In contrast, bombesin increased the activity of periventricular-hypophysial DA neurons terminating in the intermediate lobe of both male and female rats, and this was associated with a decrease in alpha MSH secretion in both sexes. Bombesin had no effect on the activities of nigrostriatal, mesolimbic, or periventricular-hypophysial DA neurons terminating in the neural lobe in either sex. The loss of endogenous gonadal hormones following ovariectomy rendered tuberoinfundibular DA neurons responsive to the stimulatory effects of bombesin, whereas immunoneutralization of endogenous prolactin following administration of prolactin antiserum had no effect on the inability of bombesin to alter the activity of these neurons in female rats.(ABSTRACT TRUNCATED AT 250 WORDS)

3,4-Dihydroxyphenylacetic Acid↗
PubMed1992

Effect of local cyanide perfusion on rat striatal extracellular dopamine and its metabolites as studied by in vivo brain microdialysis.

To investigate in vivo effects of energy failure on functions of dopaminergic neurons, we administered 0 (control), 0.2, 1 or 2 mM sodium cyanide (NaCN) dissolved in Ringer's solution for 60 min into the rat striatum through a brain microdialysis membrane. During NaCN perfusion, a transient and concentration-dependent increase in dopamine (DA) levels in the dialysate was observed. The maximum DA level during 2 mM NaCN perfusion was found to be 63-fold higher than the control levels. Leves of 3,4-dihydroxyphenylacetic acid and homovanillic acid were continuously lowered during and after NaCN perfusion. These data suggest that suppression of ATP production by NaCN induces an abrupt and remarkable increase in dopamine release from the nerve terminal in the striatum.

3,4-Dihydroxyphenylacetic Acid↗