M. Maiolini et al., EFFECTS OF SINGLE AND LONG-TERM ADMINISTRATION OF NIFEDIPINE ON DOPAMINE-RELATED BEHAVIORS, Brazilian journal of medical and biological research, 27(3), 1994, pp. 725-730
The effects of single (2.5 and 5.0 mg/kg) and long-term (2.5 mg/kg, tw
ice daily, for 30 days) ip administration of nifedipine on open-field
and apomorphine-induced stereotyped behavior were evaluated in young m
ale Wistar rats (12-16 animals per group for the open-field studies an
d 7 animals per group for the stereotypy experiments). Administration
of a single dose of nifedipine produced no changes in ambulation or re
aring frequencies or in immobility duration in the open-field compared
to controls. Similarly, treatment with a single dose of nifedipine di
d not modify apomorphine-induced stereotypy. Withdrawal from long-term
nifedipine administration caused a significant increase only in reari
ng frequency 24 h after the last drug injection (with a mean +/- SEM f
requency of 23.2 +/- 2.8 for the nifedipine group and of 14.7 +/- 2.0
for control rats, after 6-min observation). This enhancement of rearin
g frequency was no longer observed 48 h after abrupt nifedipine withdr
awal (means +/- SEM: 15.0 +/- 2.2 and 19.6 +/- 2.7 for nifedipine-trea
ted and control rats, respectively). The other open-field behavioral p
arameters and apomorphine-induced stereotypy (which was observed 96 h
after nifedipine withdrawal) were not affected by long-term nifedipine
treatment; for example, the sum of stereotypy scores (mean +/- SEM) w
as 26.9 +/- 3.0 for nifedipine-treated rats and 25.5 +/- 2.2 for vehic
le-treated animals. The possible mechanisms underlying these results a
re discussed in light of the changes in dopaminergic neurotransmission
induced by dihydropyridine calcium channel blockers.