The nucleus reticularis dorsalis: a region sensitive to physostigmine.

Microinjection of physostigmine (3 micrograms) into the nucleus reticularis dorsalis of the rat produced hypertension. Little or no increases in blood pressure were found at the other areas of the medullary reticular formation. The pressor effect following injection of physostigmine into the nucleus reticularis dorsalis was sensitive to atropine (1 microgram) but resistant to hexamethonium (5 micrograms), similarly injected. Atropine (1 microgram) bilaterally injected into the nucleus decreased pressor responses to intravenous physostigmine (100 micrograms/kg). These data may indicate that there are muscarinic receptors responsible for pressor effects in the nucleus reticularis dorsalis. The medullary cholinoceptors may be involved in the systemic physostigmine effect on blood pressure.