Evidence for presynaptic inhibition of the olfactory commissural pathway by cholinergic agonists and stimulation of the nucleus of the diagonal band

摘要: We have investigated the role of projection from magnocellular basal forebrain to olfactory bulb in regulating synaptic transmission commissural connection between two bulbs. Commissural fibers arise contralateral anterior nucleus, travel wing commissure (AC), and terminate granule cell layer bulb. Electrical stimulation causes activation cells bulb; resulting field potential is a reliable indicator this current. Microinjections cholinergic agonists, but not identical, or larger, quantities vehicle, reduced amplitude AC potential. Systemic injection scopolamine reversed depression returned response control levels. Irreversible AChE inhibition also response, muscarinic blockade effect. Cholinergic terminals entirely axons neurons nucleus diagonal band (NDB). NDB, which should release ACh, as well other transmitters, depressed response. Brief trains NDB shocks caused moderate decrease that lasted 1–2 sec. Longer shock trains, marked potentiation potential, profound, prolonged (> 20 sec) Antidromic tests demonstrated significantly decreased excitability terminals. This characteristics strongly suggest by agonists due presynaptic leading transmitter These results one function As has been implicated theta pacemaker input bulb, phasic centrifugal afferents could coordinate signal processing temporally system. Temporal coordination may be particularly important circuit function, system lacks point-to-point topographical organization characteristic sensory systems.