Depressor neurons in rabbit caudal medulla act via GABA receptors in rostral medulla

W.W. Blessing

Department of Medicine, Centre for Neuroscience, flinders University of South Australia, Bedford Park, 5042 South Australia, Australia

This article is an older article by Blessing. This laboratory investigated whether cardiovascular responses can be affected by CVLM and if RVLM is necessary for the transmission of the signal. They used microinjection technique, in order to investigate their question. Using male rabbits, they recorded from the renal nerve along with the arterial pressure and heart rate. They used horseradish peroxidase for histological identification of the areas that they injected into. Microinjections of bicuculline (bic), a GABA_A  receptor antagonist at different doses into the RVLM was done. Then after every bic microinjection they waited 5 minutes and then glutamate was injected in the CVLM.  For another group of rabbits they used a mixed agonist antagonist (Muscimol and bic) that was microinjected into the RVLM and then they either microinjected strychnine (glycine blocker) or Phenotolamine (α-adrenergic receptor blocker) and then injected glutamate in the CVLM and recorded the responses. What they found by doing the following experiments was that GABA is playing a role in modulating RVLM effects on sympathetic output by acting on GABA receptors in the RVLM. Also they found that CVLM does release GABA that acts on the GABA receptors in the RVLM to decrease sympathetic output. Finally they demonstrated that CVLM has an effect on cardiovascular responses by acting on GABA receptors in the RVLM and not by acting on glycine and α-adrenergic receptors.