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The effects of dihydropyridine compounds in behavioural tests of dopaminergic activity
Author(s) -
Bourson Anne,
Gower Alma J.,
Mir Anis K.,
Moser Paul C.
Publication year - 1989
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1989.tb12679.x
Subject(s) - nifedipine , apomorphine , dihydropyridine , amphetamine , nomifensine , chemistry , pharmacology , endocrinology , dopaminergic , medicine , anesthesia , calcium , dopamine
1 The effects of the dihydropyridine calcium channel blocker nifedipine and the activator Bay K 8644 were investigated in different behavioural tests involving dopaminergic systems. These were the discriminative stimulus induced by amphetamine, rotational behaviour in rats with unilateral 6‐hydroxydopamine (6‐OHDA) lesions and apomorphine‐induced yawning in rats. 2 The yawning induced by apomorphine (40 μg kg −1 s.c.) was significantly potentiated by nifedipine (5–10 mg kg −1 i.p.). Bay K 8644 (0.05‐0.5 mg kg −1 i.p.) dose‐dependently inhibited yawning induced by apomorphine (80 μg kg −1 s.c.) and, at 0.4 mg kg −1 , inhibited the nifedipine potentiation of apomorphine‐induced yawning. In contrast to their effects on apomorphine‐induced yawning, nifedipine and Bay K 8644 had no effect on apomorphine‐induced penile erection. 3 Bay K 8644 (0.06‐0.5 mg kg −1 i.p.) and nifedipine (5–20 mg kg −1 i.p.) had no dose‐related effect on the discrimination performance of rats trained to discriminate amphetamine from saline. However, nifedipine dose‐dependently reduced the response rate of amphetamine‐treated rats. Bay K 8644 had no effect on this measure except at high doses that also caused disruption. 4 Neither nifedipine (5–10 mg kg −1 i.p.) nor Bay K 8644 (0.06‐0.5 mg kg −1 i.p.) affected the turning behaviour induced by amphetamine (1 mg kg −1 i.p.) in rats with unilateral 6‐OHDA lesion of the medial forebrain bundle, and did not induce turning themselves. 5 As the dihydropyridine compounds affected apomorphine‐induced yawning but not penile erection, and did not affect amphetamine‐induced rotation or drug discrimination, it seems unlikely that they are affecting dopamine release in vivo.