Reciprocal connection between nucleus ambiguus and caudal ventrolateral medulla.

To investigate interactions between parasympathetic preganglionic neurons in the nucleus ambiguus (NA) and sympathoinhibitory neurons in the caudal ventrolateral medulla (CVLM) the activity of CVLM neurons was recorded during glutamate stimulation of cardioinhibitory sites in the NA of urethane-anesthetized rats. Neurons in the CVLM were identified as cardiovascular neurons if they increased their activity after i.v.

Nucleus ambiguus inhibits activity of cardiovascular units in RVLM.

To investigate interactions between sites in the medulla which control the sympathetic (SNS) and the parasympathetic (PNS) nervous system, the activity of cardiovascular neurons in the rostral ventrolateral medulla (RVLM) was recorded during chemical stimulation of cardioinhibitory neurons in the nucleus ambiguus (NA). Cardioinhibitory sites in the NA were identified in urethane anesthetized rats. The spontaneous activity of single units in the RVLM was recorded and cardiovascular units were identified as units which displayed a cardiac cycle-related rhythmicity (CR) and decreased activity after i.

Insulin microinjection into the nucleus tractus solitarii of the rat attenuates the baroreceptor reflex.

The presence of insulin and insulin binding sites in the central nervous system and the demonstration that central insulin has an effect on cardiovascular function has led to the hypothesis that insulin may play a role in mediating the baroreceptor reflex. To investigate this possibility, insulin was microinjected into depressor sites in the nucleus tractus solitarius (NTS), the first central synapse of the baroreceptor reflex, of urethane anesthetized rats. Microinjection of insulin into the NTS (110 nL of 1, 10 and 100 IU/mL) did not change mean arterial pressure (MAP) or heart rate (HR).

Influence of GABAergic mechanisms on baroreceptor inputs to nucleus tractus solitarii of rats.

The firing frequency of baroreceptive neurons in the nucleus tractus solitarii (NTS) during microiontophoretic application of muscimol, a gamma-aminobutyric acid (GABA)A agonist, or baclofen, a GABAB agonist, was monitored in anesthetized rats. Muscimol decreased the spontaneous discharge of 69 of 73 (94.5%) NTS baroreceptive neurons without affecting the remaining four neurons (5.

Role of ventrolateral medulla in reflex cardiovascular responses to activation of skin and muscle nerves.

Central neuronal circuits mediating reflex cardiovascular responses to skin and muscle nerve stimulation were studied in rats under urethan anesthesia. Responses of right rostral ventrolateral medulla (RVLM) and caudal ventrolateral medulla (CVLM) cardiovascular neurons to stimulation of contralateral skin and muscle afferent fibers were investigated. Stimulation of the tibial (muscle) nerve excited 19 (86%) of 22 CVLM neurons and inhibited 18 (82%) of 22 RVLM neurons.