Life-long dietary restriction affects striatally-mediated behavioral responses in aged rats

The effects of life-long dietary restriction on rotational behavior and stereotypy induced by intrastriatally administered dopamine-excitatory (dopamine, DA; amphetamine, AMPH) or cholinergic inhibitory (atropine, AT) agents were examined in rats. Three groups of male Wistar rats were used; mature ad lib (YAL, 6 month), old ad lib (OAL 24 month), and old restricted animals (OR). OR animals were fed and fasted on alternate days from weaning. Each rat was unilaterally lesioned in the left substantia nigra with 6-hydroxydopamine and a cannula was implanted in the right caudate nucleus. Several doses of each drug [AT (0, 1, 7, micrograms) DA (0, 5, 50 micrograms), and AMPH (0, 2, 5, 5, 10 micrograms)] were given randomly (1 dose/day with 1 week between drugs). All doses of a particular drug were given before the next drug regimen was started. A combination of AMPH (25 micrograms) and AT (1 microgram) was also administered in one injection at the completion of all other regimens. Results showed that OR animals responded as well as YAL animals and far better than OAL animals following AMPH, DA, or low doses of AT. However, both the high dose of AT and the combined dose of AMPH-AT seemed to suppress responding in OR animals. Neither AT alone or AMPH-AT combinations had effects in OAL animals. Results are discussed in terms of the possible specificity of effects of dietary restriction on striatal functioning and behavior in senescence.