Post-training intra-striatal scopolamine or flupenthixol impairs radial maze learning in rats

Abstract

Systemic treatments with acetylcholine (ACh) or dopamine (DA) receptor antagonists during hours 0–4 but not during hours 5–8 following training on a radial arm maze (RAM) or lesions of the dorsal striata impair learning. This suggested that intra-striatal infusions of ACh or DA receptor antagonists during hours 0–4 following training may impair learning. Rats were randomly assigned to groups (ns = 5–11) receiving dorsal striatal infusions of the ACh receptor antagonist scopolamine (0–18 μg/μL at 0 and 2 h or at 4 and 6 h after training), the DA receptor antagonist cis-flupenthixol (0–25 μg/μL at 0, 4 or 12 h after training) or the inactive isomer trans-flupenthixol (6 μg/μL at 0 h after training). Scopolamine and cis-flupenthixol impaired the habit-learning version of the task. Given after hours 0–4 following training, the effects of scopolamine were diminished but those of cis-flupenthixol were not. Trans-flupenthixol produced less impairment than cis-flupenthixol. Results suggest that ACh and DA receptors in the dorsal striatum during hours 0–4 following training play a role in habit learning.