Journal of the autonomic nervous system
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J. Auton. Nerv. Syst. · Nov 1989
Modification of spino-bulbar autonomic cholinergic systems by activation of alpha-adrenergic receptors.
Intrathecal (i.t.) injection of neostigmine was employed to activate spinal cholinergic neurons mediating a hypertensive response in freely-moving rats. Our earlier studies have demonstrated that stimulation of central alpha-adrenergic receptors inhibits the pressor response following inhibition of brain cholinesterase. Clonidine (0.5-5 micrograms) pretreatment by i.t. injection did not alter the magnitude of the pressor response to i.t. injection of neostigmine, but did significantly delay the onset of the response. ⋯ Depletion of medullary acetylcholine significantly blocked the pressor response to i.t. injection of carbachol. These findings are consistent with the concept of an ascending spinal cholinergic pressor pathway. The pressor response to activation of spinal cholinergic receptors is not sensitive to local injection of clonidine, but, the medullary cholinergic component of the system is inhibited by alpha-receptor stimulation.