alpha-Adrenoceptor and opioid receptor modulation of clonidine-induced antinociception.

1. The antinociceptive action of clonidine (Clon) and the interactions with alpha 1, alpha 2 adrenoceptor and opioid receptor antagonists was evaluated in mice by use of chemical algesiometric test (acetic acid writhing test). 2.

Cholinergic stimulants and excess potassium ion increase the fluidity of plasma membranes isolated from adrenal chromaffin cells.

Chromaffin cell membranes from the bovine adrenal medulla were labelled with the hydrophobic fluorescent probe 1,6-diphenyl-1,3,5-hexatriene, and the fluorescence polarization (P) of the membrane suspensions was measured as a function of temperature. The P versus t profiles, between 20 and 37 degrees C, showed two linear regions separated by a break in the vicinity of 30 degrees C, reflecting a change in the phase behaviour of the constitutent lipids. Decreases in P values at higher temperature indicated progressive fluidization of the lipid bilayer.

Chronic effects of nicotine on catecholamine synthesizing enzymes in rats.

The effects of chronic administration of nicotine upon catecholamine (CA) synthesizing enzymes of rat hypothalamus, striatum and adrenal medulla were studied. Nicotine 3 mg/kg/day for 14 days, increased tyrosine hydroxylase (TH) and dopamine-beta-hydroxylase (DBH) in hypothalamus and adrenal medulla but did change striatum TH. The data suggest that chronic nicotine administration can produce similar long-term alterations in both of the main CA forming enzymes in the hypothalamus and in adrenal medulla.