Possible contribution of central gamma-aminobutyric acid receptors to resting vascular tone in freely moving rats.
Previous studies have shown that central administration of GABA (gamma -aminobutyric acid), an inhibitory neurotransmitter, preferentially reduces hindquarters and carotid vascular resistances but not renal and coeliac vascular resistances in conscious rats. This study tested the hypothesis that these preferential actions of central GABA receptors are related to differences between vessels in resting autonomic vascular tone in freely moving rats. Rats were chronically implanted with intracisternal cannulas and/or electromagnetic probes to measure regional blood flows. In response to GABA administration, the changes in vascular resistance (arterial blood pressure/regional blood flow) of the hindquarters (n = 23) and carotid (n = 12) vascular beds were significantly and negatively correlated with basal vascular resistance. No such relationship was found for the renal (n = 21), coeliac (n = 13) and superior mesenteric (n = 23) vascular beds. This finding indicates that the responsiveness to GABA of brainstem pathways controlling the hindquarters and carotid vascular beds co-varies with resting resistance in hindquarters and carotid vessels. A similar analysis was performed, correlating the ongoing vascular resistance of each vessel with its response to ganglionic blockade by chlorisondamine. In this case, a significant negative correlation was also found for the hindquarters (n = 26) and carotid (n = 15) vascular beds, but not for the coeliac (n = 17) or superior mesenteric (n = 19) vessels. Together, these findings suggest that central GABA receptors accessible from the cisterna magna preferentially affect two vascular beds which, in the freely moving rat, show resting autonomic vascular tone.
Takemoto
Y
Y
Department of Physiology, Hiroshima University Faculty of Medicine, Kasumi 1-2-3, Minami-ku, Hiroshima 734-8551, Japan. yumitake@hiroshima-u.ac.jp
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology; D002339:Carotid Arteries / Q000187:drug effects / Q000502:physiology; D002714:Chlorisondamine / Q000494:pharmacology; D005730:Ganglionic Blockers / Q000494:pharmacology; D006339:Heart Rate / Q000187:drug effects; D008297:Male; D009068:Movement / Q000502:physiology*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D018079:Receptors, GABA / Q000502:physiology*; D012039:Regional Blood Flow / Q000187:drug effects / Q000502:physiology; D012079:Renal Circulation / Q000187:drug effects / Q000502:physiology; D013152:Splanchnic Circulation / Q000187:drug effects / Q000502:physiology; D014655:Vascular Resistance / Q000187:drug effects / Q000502:physiology*; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology
D005730:Ganglionic Blockers; D018079:Receptors, GABA; D005680:gamma-Aminobutyric Acid; D002714:Chlorisondamine