Activity of adenylate cyclase and 5'-nucleotidase in the sensorimotor and limbic structures of the brain in rats after manipulatory training.

Adenylate cyclase (AC) and 5'-nucleotidase (NT) activities were measured in the limbic (amygdala, hippocampus) and sensorimotor (cortex, striatum) structures of the brain in three groups of rats: untrained rats and rats which were good and poor learners in training to perform movements involving pushing against an obstruction. After training, AC activity decreased in all structures studied. Activity decreased in the cortex and striatum to a greater extent in good learners, and in the amygdala in poor learners. NT activity decreased in all brain structures apart from the striatum, to a greater extent in rats which were less able to learn to produce movements involving prolonged pushing. The striatum was the only structure in which increases in NT activity occurred, from the lowest initial level in the control group. 1.0 +/- 0.04 microgram P(i)/mg protein/min, to 1.3 +/- 0.1 micrograms P(i)/mg protein/min in poor learners and to 2.0 +/- 0.1 micrograms P(i)/mg protein/min in good learners. Interhemisphere asymmetries in AC activity in the cortex and hippocampus were seen, along with an interhemisphere difference in NT activity in the amygdala. Thus, the activity of enzymes involved in adenine and cAMP biosynthesis changed in different ways in the limbic and sensorimotor structures of the brain, depending on the ability of rats to learn. The increase in NT activity after training of rats, which was limited to the striatum, may reflect a special role for the purinergic system in these structures in mediating sensation-regulated movements.