Article date: October 1991
By: Simon C.E. Sporton, Sara L. Shepheard, David Jordan, Andrew G. Ramage, in Volume 104, Issue 2, pages 466-470
The effects of microinjections (100 nl) into the dorsal motor vagal nucleus of the 5‐HT1A receptor agonists 8‐hydroxy‐2‐(di‐n‐propylamino)tetralin (8‐OH‐DPAT) and flesinoxan, the 5‐HT2 receptor agonist (±)‐1‐(2,5‐dimethoxy‐4‐iodophenyl)‐2‐aminopropane hydrochloride (DOI), the 5‐HT3 receptor agonist phenylbiguanide (PBG), the α2‐adrenoceptor agonist clonidine and the excitatory amino acid glutamate on heart rate, blood pressure, tracheal pressure and phrenic nerve activity were investigated in atenolol‐pretreated rats anaesthetized with sodium pentobarbitone.
Microinjections of glutamate (2.5 nmol) caused decreases in blood pressure, heart rate and phrenic nerve activity. In contrast, microinjections of 5‐HT (1.2 nmol), 8‐OH‐DPAT (1.2 nmol) and flesinoxan (1.3 nmol) all caused a bradycardia but had no effect on blood pressure. In addition, 8‐OH‐DPAT and flesinoxan caused an increase in phrenic nerve activity.
Microinjections of DOI, PBG and clonidine had no significant effect on any of the variables recorded. None of the drugs used had any significant effect on tracheal pressure.
These results support the hypothesis that activation of 5‐HT1A receptors causes excitation of cardiac vagal motoneurones and suggest that these receptors are also important in the control of central respiratory drive.
The effects of microinjections (100 nl) into the dorsal motor vagal nucleus of the 5‐HT1A receptor agonists 8‐hydroxy‐2‐(di‐n‐propylamino)tetralin (8‐OH‐DPAT) and flesinoxan, the 5‐HT2 receptor agonist (±)‐1‐(2,5‐dimethoxy‐4‐iodophenyl)‐2‐aminopropane hydrochloride (DOI), the 5‐HT3 receptor agonist phenylbiguanide (PBG), the α2‐adrenoceptor agonist clonidine and the excitatory amino acid glutamate on heart rate, blood pressure, tracheal pressure and phrenic nerve activity were investigated in atenolol‐pretreated rats anaesthetized with sodium pentobarbitone.
Microinjections of glutamate (2.5 nmol) caused decreases in blood pressure, heart rate and phrenic nerve activity. In contrast, microinjections of 5‐HT (1.2 nmol), 8‐OH‐DPAT (1.2 nmol) and flesinoxan (1.3 nmol) all caused a bradycardia but had no effect on blood pressure. In addition, 8‐OH‐DPAT and flesinoxan caused an increase in phrenic nerve activity.
Microinjections of DOI, PBG and clonidine had no significant effect on any of the variables recorded. None of the drugs used had any significant effect on tracheal pressure.
These results support the hypothesis that activation of 5‐HT1A receptors causes excitation of cardiac vagal motoneurones and suggest that these receptors are also important in the control of central respiratory drive.
DOI: 10.1111/j.1476-5381.1991.tb12452.x
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