Chronic nicotine treatment delays the developmental increase in brain muscarinic receptors in rat neonate

Developmental increase in the muscarinic receptors ([³H]quinuclidinyl benzylate binding sites) of rat neonate brain (cerebral cortex and cerebellum) was significantly inhibited by chronic nicotine treatment of the dams during pregnancy and lactation. However, development of the nicotinic receptors ([³H]cytisine binding sites) was not inhibited and rather was up-regulated in the cerebral cortex and brainstem by the nicotine treatment. Such inhibition and up-regulation were not seen in nicotine-withdrawn rats after birth. These results suggest that nicotine treatment during lactation may cause a remarkable delay in development of muscarinic neurotransmission in rat neonates.