Nucleus A10 dopaminergic neurons in inbred mouse strains: firing rate and autoreceptor sensitivity are independent of the number of cells in the nucleus.
Inbred mouse strains have different numbers of midbrain dopaminergic neurons; for example, BALB/cJ mice have 20-25% more neurons than CBA/J mice. As the number of cells decrease, for example in Parkinson's disease and in animals with midbrain dopaminergic cell lesions, the activity of their remaining cells increases. The purpose of the present experiment was to determine whether the functional properties of dopaminergic neurons in the ventral tegmental area (nucleus A10) differ in inbred mouse strains which possess different numbers of cells. The firing rate and autoreceptor sensitivity of A10 dopaminergic cells were examined in the in vitro slice preparation in BALB/cJ, C3H/HeJ, CBA/J, and DBA/2J mouse strains. It was observed that the autoreceptors on mouse dopaminergic neurons exhibit pharmacological properties of dopamine autoreceptors; activation of the autoreceptor produced a marked inhibition (50-70%) in cell firing rate by quinpirole (10(-8) M), LY-141865 (10(-7) M), (+)-3-(3-hydroxyphenyl)-N-n-propyl-piperidine (10(-6) M), propyl-norapomorphine (10(-5) M) and dopamine (10(-4) M), and this inhibition was blocked or reversed by specific dopamine D2 receptor antagonists [(-) sulpiride and spiroperidol, 10(-6) M]. The baseline firing rates of the A10 cells did not differ among the four inbred strains [range 2.5 +/- 0.2 (C3H/HeJ)-3.4 +/- 0.3 (CBA/J) spikes/s +/- SEM], and there was no significant difference in autoreceptor sensitivity among the mouse strains as assessed either by superfused dopamine (inhibitory dose 50% approximately 150 microM), or by superfused quinpirole (inhibitory dose 50% approximately 10 nM).(ABSTRACT TRUNCATED AT 250 WORDS)
Bernardini
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GL
Department of Physiology, University of Texas Southwestern Medical Center, Dallas 75235-9070.
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German
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D000818:Animals; D002452:Cell Count; D004298:Dopamine / Q000494:pharmacology / Q000502:physiology*; D004594:Electrophysiology; D051379:Mice; D008815:Mice, Inbred Strains / Q000502:physiology*; D009474:Neurons / Q000378:metabolism / Q000502:physiology*; D011954:Receptors, Dopamine / Q000378:metabolism*; D013681:Tegmentum Mesencephali / Q000166:cytology*
D011954:Receptors, Dopamine; D004298:Dopamine