Biogenic amines were injected into the caudate nuclei of awake, freely moving rats through cannulae implanted 1 week previously. After injections the brains were freeze-dried and treated with formaldehyde vapors according to the method of Falck and Hillarp. Intrastriatal spreading was determined by fluorescence microscopy. Intrastriatal spread of catecholamines related directly to both concentration and osmolality of injected amine. Dopamine and norepinephrine, 1 μg in 1 μl saline, for example, were found to spread rostral-caudally mean total distances of 2.11 and 1.88 mm, respectively. Intrastriatal spreading was affected by dexamethasone and mannitol, which reduced rostral-caudal spreading of dopamine by more than 50% when administered prior to intrastriatal injection. Spreading of serotonin through brain tissue could not be determined. These data suggest that the spreading of exogenous catecholamines through cerebral tissues may occur through extracellular channels. The observed rate of spreading (about 0.5 mm/min) and electron microscopic analysis were consonant with this interpretation.
ASJC Scopus subject areas
- Developmental Neuroscience