Ovarian
hormones, such as
estrogens and
progesterone, are known to exert beneficial effects on cognition and some
psychiatric disorders. The basis of these effects is not fully understood, but may involve altered
cholinergic neurotransmission. This study aimed to investigate how a lack of ovarian
hormones would impact
muscarinic receptor-induced deficits in prepulse inhibition (PPI) and
muscarinic receptor density in several brain regions. Adult female rats were either ovariectomized, to remove the source of ovarian
hormones, or left intact (
sham-operated). PPI is a measure of sensorimotor gating that is typically impaired in
schizophrenia patients, and similar deficits can be induced in rats by administering
scopolamine, a
muscarinic receptor antagonist. Our results revealed no significant effects of
ovariectomy on PPI after saline or
scopolamine treatment. Autoradiography was performed to measure
cholinergic muscarinic receptor binding density using [3H]-
pirenzepine, [3H]-AF-DX, and [3H]-4-DAMP, to label M1, M2/M4, and M3 receptors, respectively. We examined the amygdala, caudate putamen, dorsal hippocampus, motor cortex, retrosplenial cortex, and ventromedial hypothalamus. There were no significant group differences in any region for any
muscarinic receptor type. These results suggest that removing peripheral ovarian
hormones does not influence the
cholinergic muscarinic receptor system in the context of PPI or receptor binding density.