Activation of mesencephalic dopamine neurons by chemical stimulation of the nucleus tegmenti pedunculopontinus pars compacta.
Unilateral stereotaxic microinjection of a small amount of kainic acid (KA) into the nucleus tegmenti pedunculopontinus pars compacta (TPC) of male Wistar rats produced constant ipsiversive circling behavior. The rate of the TPC-derived circling was significantly attenuated by blocking agents of dopamine systems, including haloperidol and alpha-methyl-tyrosine (both injected intraperitoneally) and also 6-hydroxydopamine (injected into the bilateral medial forebrain bundles). Administration of norepinephrine antagonists (phenoxybenzamine hydrochloride and DL-propranolol) had no effect on the rate of the TPC-derived circling. Bilateral preinjections of atropine sulfate into the ventral midbrain tegmentum, including the ventral tegmental area and the pars compacta of the substantia nigra, significantly attenuated the rate of the circling. The unilateral KA injection into the TPC dramatically increased the ratio of HVA + DOPAC/dopamine, an indicator of dopamine turnover, in the nucleus accumbens as well as in the striatum bilaterally. The increase of the ratio in the nucleus accumbens was selectively suppressed by pretreatment with atropine sulfate administered into the bilateral ventral midbrain tegmentum. These facts indicate: (1) the TPC-derived circling behavior is mediated by the dopamine system, (2) the chemical stimulation of TPC by KA might produce an activation of midbrain dopamine neurons by excitatory TPC efferents to the dopamine neurons and enhance the dopamine turnover in the nucleus accumbens as well as in the striatum, (3) the excitatory TPC efferents may be muscarinic cholinergic in accordance with previous reports.
Niijima
K
K
Department of Neurology, Jichi Medical School, Tochigiken, Japan.
Yoshida
M
M
D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects / Q000502:physiology; D004298:Dopamine / Q000502:physiology*; D007608:Kainic Acid / Q000494:pharmacology; D008297:Male; D008636:Mesencephalon / Q000187:drug effects / Q000502:physiology*; D009474:Neurons / Q000502:physiology; D051381:Rats; D011919:Rats, Inbred Strains
D007608:Kainic Acid; D004298:Dopamine