Interaction of the neuropeptides substance P and neurotensin with central monoamine transmitter systems
Singer, E.
Wiener Klinische Wochenschrift 96(22): 809-816
1984
ISSN/ISBN: 0043-5325 PMID: 6084908 Document Number: 240817
In the present paper, findings on two neuropeptides, substance P (SP) and neurotensin (NT), are presented and discussed with respect to a neuromodulatory role of these peptides on brain monoamine transmitter systems. Substance P: In view of the close morphological relationship of serotonin-(5-HT-) and SP-neurons in the brainstem of the rat the effect of SP was studied in vitro on the field stimulated release of 3H-5-HT from slices of medulla oblongata. Substance P enhanced the electrically induced release of 3H-5-HT without affecting the basal release. Furthermore, the immunohistochemical evidence for the coexistence of SP and 5-HT in neurons of this area was corroborated by employing neurochemical lesioning techniques. Neurotensin: Binding sites for NT in the substantia nigra and the ventral tegmentum of the rat were decreased after stereotaxic injection of the neurotoxin 6-hydroxydopamine, which specifically destroys catecholamine-containing neurons. The results indicate a localization of NT-receptors on dopaminergic neurons in these regions. In the striatum and the nucleus accumbens, the field stimulated release of 3H-dopamine in vitro was markedly and dose-dependently increased in the presence of NT, demonstrating a direct effect of the peptide on dopamine-containing nerve terminals. In the medial preoptic nucleus, a high density of NT-binding sites was measured and stereotaxically microinjected NT caused a rise in plasma levels of luteinizing hormone (LH). Concomitantly, noradrenaline levels in the injected region were significantly reduced. The results favour an interaction of NT and noradrenergic neurons in the hypothalamic control of LH secretion.