Pharmacology of Synaptic Ganglionic Transmission and Second Messengers

Neurobiology of Acetylcholine

“…Two such actions were demonstrated: first, a majority of motoneurons was excited by ACh primarily via muscarinic receptors; only a small portion of motoneurons being activated by nicotinic stimulation; second, ACh depressed synaptic transmission in motoneurons by acting at a presynatpic muscarinic site (Jiang and Dun, 1986).…”

“…Furthermore, superfusion of the slices with strychnine (1 ~M) and/or bicuculline (1 ~M) did not modify the inhibitory action of ACh on the EPSPs. Collectively, the results suggest that ACh depresses synaptic transmission by a presynaptic mechanism as it activates presynaptic muscarinic receptors thus reducing the release of the transmitter (Jiang and Dun, 1986).…”

“…The depression was not due to membrane depolarization induced by ACh as returning the membrane potential to the resting level did not restore the EPSP amplitude (Jiang and Dun, 1986). The depolarization as well as the synaptic depression caused by ACh was effectively prevented by pretreating the slice with atropine but not with d-Tc (Fig.…”

“…The procedures used in obtaining thin transverse (400-500 ~m) slices of thoracolumbar spinal cord from neonatal rats have been described earlier (Ma and Dun, 1985Dun, , 1986. The slices with ventral and dorsal rootlets were transferred to the recording chamber and continuously super fused with a Krebs solution saturated with 95% 0 3 and 5% CO 2 ; the temperature of the solution was maintained at 34 + 0.5 C. Intracellular recordings were obtained from neurons situated-in the ventral horn by means of glass microelectrodes filled with 3}f K acetate; the impedance of the microelectrodes varied between 30 and 100 M0.…”