Record 5 of 7 in BA on CD January - June 1991

Title

Nicotinic and muscarinic cholinergic receptors in honey bee (Apis mellifera) brain.

Author(s)

HUANG-Z-Y; KNOWLES-C-O

Source Journal

COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY C COMPARATIVE PHARMACOLOGY AND TOXICOLOGY 97(2): 275-282

Publication Year

1990

Language of Article

English

Abstract

Honey bee head homogenates contained particulate components capable of binding the nicotinic receptor antagonist alpha-bungarotoxin (BGT) and the muscarinic receptor antagonist quinuclidinyl benzilate (QNB). Specific binding of (125I)BGT (defined by nicotine) and (3H)QNB (defined by atropine) was heat sensitive, linear with tissue concentration, and saturable. B-max values were 204 fmol mg protein-1 for (125I)BGT and 57 fmol mg protein-1 for (3H) QNB yielding a binding site ratio of 3.6:1. Hill coefficients were 1.0 for each radioligand. Binding by both radioligands was rapid and reversible. Association (k+1) and dissociation (K-1) rates were 1.38 times 10-6 s-1 M-1 and 6.2 times 10-4 s-1 for (125I)BGT and 3.27 times 10-5 s-1 M-1 and 9.4 times 10-5 s-1 for (3H)QNB. The dissociation rate constants (K-D) were 450 pM (k-1/k+1) and 743 pM (saturation) for (125I)BGT and 30 pM (k-/k+1) and 96 pM (saturation) for (3H)QNB. Pharmacological profiles were nicotinic for (125I)BGT with nicotine (K-i 2.6 times 10-7 M), D-tubocurarine K-i 1.0 *x 10-6 M), and ACh + dichlorvos (K-i 4.5 times 10-6 M) being the most potent inhibitors and muscarinic for (3H)QNB with (+-)-QNB (K-i 2.2 times 10-12 M), S(+)-dexetimide (K-i 2.9 times 10-11 M), atropine (K-i 6.9 times 10-10 M), and scopolamine (K-i 4.1 times 10-10 M) being most potent. It appeared that (125I)BGT and (3H)QNB were binding with high affinity to honey bee brain populations of nicotinic and muscarinic cholinergic receptors, respectively. .