Modulating effect of adenosine on the hypertensive response to physostigmine.

ABSTRACT

The purpose of this work was to study the neuromodulatory role of adenosine on the hypertensive response to physostigmine in the rat. It was found that increasing doses of adenosine, injected intravenously, produced a biphasic blood pressure response, consisting of an initial and short-lasting hypotension, followed by a prolonged hypertension. The hypertensive phase of this response was significantly depressed or even abolished by phentolamine, whereas the hypotensive phase was depressed but not abolished by atropine. If injected intravenously, but immediately before physostigmine, adenosine produced a potentiation of the blood pressure response to physostigmine. This was even more evident if adenosine was injected directly into the carotid artery immediately before the intravenous injection of physostigmine. Neither aminophylline nor 8-phenyltheophylline affected this potentiating action of adenosine. This finding might indicate that this potentiating action does not involve the already known adenosine receptors, or that this action is realized through some other type of receptors and mechanisms not sensitive to xanthine derivatives. It is concluded that adenosine might have a general modulating presynaptic effect on various transmitting processes, including those which take place in the central nervous system during the hypertensive response to physostigmine in the rat.