The effect of microinjection of amino acids into the nucleus tractus solitarius on the diving bradycardia in the rat.
The role of nucleus tractus solitarius (NTS) in the diving bradycardia was studied in anesthetized rats. The floor of the 4th ventricle of the medulla was exposed and 0.1 microliters of the test agent was injected into NTS bilaterally. The simulated diving (head immersion) for 30 sec was performed before and after the injection. Blood pressure and heart rate were monitored. Before the treatment, heart rate decreased by 51% and blood pressure rose by 23% during the diving in the pooled data (n = 35). Injection of glutamate (0.1-1 mM) or CaCl2 (100 mM) into NTS attenuated the diving bradycardia, but that of GABA (0.1 mM), glycine (0.1 mM), KCl (100 mM) or saline solution did not affect the diving bradycardia significantly. Lesions of NTS also attenuated the diving bradycardia. These data suggest that NTS may play a role in modulation of the diving response.
Huang
T F
TF
Department of Physiology, College of Medicine, National Taiwan University, Taipei, Republic of China.
Peng
Y I
YI
Huang
L L
LL
D000596:Amino Acids / Q000494:pharmacology*; D000818:Animals; D001794:Blood Pressure / Q000502:physiology; D001919:Bradycardia / Q000503:physiopathology*; D002118:Calcium / Q000378:metabolism; D002412:Cations / Q000378:metabolism; D004242:Diving; D005971:Glutamates / Q000378:metabolism; D005998:Glycine / Q000378:metabolism; D008526:Medulla Oblongata / Q000502:physiology*; D008845:Microinjections; D011188:Potassium / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D012964:Sodium / Q000378:metabolism; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
D000596:Amino Acids; D002412:Cations; D005971:Glutamates; D005680:gamma-Aminobutyric Acid; D012964:Sodium; D011188:Potassium; D002118:Calcium; D005998:Glycine