In vivo electrochemical demonstration of potassium-evoked monoamine release from rat cerebellum.

In vivo electrochemical methods were employed to study the potassium (K+)-evoked release of monoamines from the cerebellum of the chloral hydrate anesthetized rat. K+-evoked releases were elicited using micropipette-Nafion-coated graphite epoxy electrode arrays in the granule/Purkinje cell layer, molecular layer, and white matter. These recorded releases were generally found to be reversible, moderately dose-dependent, and reproducible. However, the temporal dynamics of the releases were different for the cell layer versus molecular layer records. Releases were infrequently observed in cerebellar white matter, an area which is relatively devoid of monoamine containing terminals. The signals recorded from the cell and molecular layers were significantly attenuated by pretreatment with the selective noradrenergic neurotoxin, N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine (DSP-4). Local pretreatment with nomifensine, a potent catecholamine reuptake blocker, significantly prolonged the K+-evoked signals observed in both the granule/Purkinje cell and molecular layers. These data, taken together with earlier reports on the electrophysiological responses to activation of cerebellar noradrenergic inputs, support the conjecture that in vivo electrochemical recording methods have the sensitivity and spatial resolution for studies of functional monoamine release from brain regions that have a diffuse or laminated monoamine innervation.