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Neurophysiological investigation of effects of the D‐1 agonist SKF 38393 on tonic activity of substantia nigra dopamine neurons
Author(s) -
Carlson Joanne H.,
Bergstrom Debra A.,
Weick Barton G.,
Walters Judith R.
Publication year - 1987
Publication title -
synapse
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.809
H-Index - 106
eISSN - 1098-2396
pISSN - 0887-4476
DOI - 10.1002/syn.890010505
Subject(s) - quinpirole , substantia nigra , autoreceptor , pars compacta , dopamine , agonist , chemistry , apomorphine , dopamine agonist , dopamine receptor , stimulation , pars reticulata , endocrinology , medicine , pharmacology , neuroscience , receptor , dopaminergic , biology , biochemistry
The effects of the D‐1 agonist SKF 38393 on tonic activity of rat substantia nigra pars compacta dopamine neurons were studied using extracellular, single‐unit recording techniques. Unlike nonselective D‐1/D‐2 dopamine agonists or the D‐2 agonist quinpirole, SKF 38393 did not inhibit dopamine neuronal activity when applied iontophoretically or when administered intravenously in doses up to 20 mg/kg to chloral hydrateanesthetized rats. Moreover, pretreatment with SKF 38393 did not alter the inhibitory response of these neurons to apomorphine or the D‐2 agonist quinpirole. However, in locally anesthetized, gallamine‐treated, artificially respired rats, dopamine cell activity was significantly altered by i.v. administration of SKF 38393; firing rate increases and decreases were observed. Administration of the inactive enantiomer of SKF 38393, S‐SKF 38393, did not induce similar changes in parallel experiments. These results support the idea that unlike D‐2 autoreceptor stimulation, D‐1 receptor stimulation does not exert a direct local effect on dopamine neurons in the substantia nigra pars compacta and suggest that D‐1 receptor stimulation at sites postsynaptic to the dopamine cells may indirectly affect the activity of some dopamine neurons through long‐loop feedback mechanisms.