Regional responses of rat brain muscarinic cholinergic receptors to immobilization stress.
The effect of immobilization stress (IM-stress) on the muscarinic cholinergic (m-Ch) receptor binding was determined in 8 brain regions using [3H]quinuclidinyl benzilate (QNB). IM-stress produced an increase in specific QNB binding in the septum, striatum, hippocampus and pons + medulla oblongata. Scatchard analysis revealed that IM-stress produced an increase in the affinity of m-Ch receptors in the septum, hippocampus and pons + medulla oblongata, but did not alter the maximum number of binding sites (Bmax). In the striatum, an increase in specific QNB binding was due to both the increase in Bmax and reduction of the dissociation constant (Kd). The present study suggests that IM-stress induces supersensitivity of postsynaptic m-Ch receptors probably due to a decrease in presynaptic cholinergic activities in the septum, striatum, hippocampus and pons + medulla oblongata. As the m-Ch receptors in the striatum and pons + medulla oblongata are affected by IM-stress, further studies of the m-Ch neural system must be performed under stressful situations in these regions as well as in the septum, hippocampus and cerebral cortex.
Third Department of Internal Medicine, Okayama University Medical School, Japan.
H
H
Takayama
K
K
Mizukawa
Z
Z
Ota
N
N
Ogawa
D000818:Animals; D001921:Brain / Q000378:metabolism*; D001923:Brain Chemistry; D007103:Immobilization; D008297:Male; D011812:Quinuclidines / Q000378:metabolism*; D011813:Quinuclidinyl Benzilate / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D011976:Receptors, Muscarinic / Q000032:analysis / Q000502:physiology*; D013312:Stress, Physiological / Q000503:physiopathology*
D011812:Quinuclidines; D011976:Receptors, Muscarinic; D011813:Quinuclidinyl Benzilate