PT  - JOURNAL ARTICLE
AU  - S Ma
AU  - J P Long
AU  - R K Bhatnagar
TI  - Further studies on central actions of nitroglycerin and lack of evidence for nitroglycerin interacting on [3H]clonidine binding sites in cortex membranes.
DP  - 1992 Jun 01
TA  - Journal of Pharmacology and Experimental Therapeutics
PG  - 1187--1194
VI  - 261
IP  - 3
4099  - http://jpet.aspetjournals.org/content/261/3/1187.short
4100  - http://jpet.aspetjournals.org/content/261/3/1187.full
SO  - J Pharmacol Exp Ther1992 Jun 01; 261
AB  - Decerebration and transection of the spinal cord totally abolished the hypotensive and tachycardiac responses to i.c.v injection of nitroglycerin (NTG) and reduced the tachycardia induced by i.v. injection of the drug. The hypotensive responses to i.v. injection of sodium nitroprusside were not altered by decerebration. Microinjection of NTG (0.1-1.0 nmol) into anterior hypothalamic medial preoptic area (AH/POA) produced dose-dependent decreases in mean arterial pressure and heart rate, but minimal responses were induced when the same doses of NTG were injected into the rostral ventrolateral medulla. Pretreatment with rauwolscine (2.5 nmol), injected into the AH/POAs, antagonized the depressor responses to NTG when it was administered into the areas or given i.v. However, rauwolscine did not alter the depressor responses induced by i.v. sodium nitroprusside. Prazosin (1.5 nmol) in the AH/POA did not alter the bradycardic effects induced by microinjection of NTG into the areas. (minus)-Epinephrine significantly interacted with alpha-2 adrenoceptor binding sites, but serotonin and NTG did not interact with [3H] clonidine binding sites in cortex membranes. Results suggest that cardiovascular responses after i.v. injection of NTG involve central and peripheral component. AH/POA is one of the central sites involved in the depressor effects of NTG. NTG-induced modulation of noradrenergic transmission appears to stimulate alpha-2 adrenoceptors in the central nervous system, but the drug does not involve direct interaction with alpha-2 adrenoceptors. Hypotensive effects of sodium nitroprusside result from its action at peripheral sites.