Ameliorative effects of tachykinins on scopolamine-induced impairment of spontaneous alternation performance in mice.

The present study was designed to clarify whether opioid neuronal systems are involved in the be,beneficial effects of tachykinins such as the neurokinin NK1 receptor agonist, substance P (SP) the neurokinin NK2 receptor agonist, neurokinin A (NKA), and the neurokinin NK3 receptor agonist, senktide, on the scopolamine-induced impairment of spontaneous alternation performance in mice. Intracerebroventricular injections of SP (0.1 mu g), NKA (0.3 mu g) and senktide (3 ng) inhibited the scopolamine (1 mg/kg)-induced impairment of spontaneous alternation performance without influencing total arm energies, indicating the antiamnesic effects of tachykinins. Furthermore, the inhibitory effects of SF: but riot those of NKA or senktide, were almost completely reversed by pretreatment with naloxone (1 mg/kg). However; the effects of SP on the scopolamine-induced impairment of spontaneous alternation performance were nor influenced by pretreatment with the mu-opioid receptor antagonist, beta-funaltrexamine (5 mu g), the delta-opioid receptor antagonist naltrindole (4 ng), and the kappa-opioid receptor antagonist nor-binaltorphimine (4 mu g). These findings suggest that the effects of SP, unlike those of NKA or senktide, on the scopolamine-induced impairment of spontaneous alternation performance associated with spatial working memory are not mediated simply via a single type of opioid receptors, such as mu, delta or kappa. (C) 1998 Prous Science. All rights reserved.