Accumulation and overflow of 3H following incubation of the guinea-pig gall bladder with [3H]-noradrenaline.

Abstract

1 Strips of guinea-pig gall bladder readily accumulate (3)H following incubation in the presence of 5 x 10(-8) M (-)-[(3)H]-noradrenaline. This accumulation was reduced by lowering the incubation temperature (from 37 degrees to 23 degrees C), by cocaine (10(-6) M), by nortriptyline (10(-8), 10(-6) and 10(-4) M) and following incubation of the tissues with 6-hydroxydopamine (10(-3) M for 3 h). At 10(-6) M, (-)-noradrenaline and (-)-adrenaline, but not (-)-isoprenaline, inhibited the accumulation of (3)H.2 Following preloading of strips of guinea-pig gall bladder with 3.6 x 10(-7) M (-)-[(3)H]-noradrenaline for 1 h, the spontaneous overflow of (3)H was observed. Cocaine (10(-4) M), nortriptyline (10(-6) M), (-)-isoprenaline (10(-5) M), acetylcholine (10(-5) M) and adenosine 5'-triphosphate (ATP, 10(-4) M) had no effect on the spontaneous overflow of (3)H. KCl (10(-1) M), (-)-noradrenaline (10(-5) M), (-)-adrenaline (10(-5) M), and tyramine (10(-5) M) increased the overflow of (3)H. These results illustrate similar characteristics of the guinea-pig gall bladder to other noradrenergically-innervated tissues in accumulating and releasing (3)H following incubation in the presence of [(3)H]-noradrenaline.3 Following incubation in the presence of 3.6 x 10(-7) M (-)-[(3)H]-noradrenaline, field stimulation, at 5 Hz, of strips of gall bladder, in the absence or presence of 10(-6) M atropine, increased the overflow of (3)H and, simultaneously, induced contractions. The contractile responses to 5 Hz were smaller in the presence than in the absence of 10(-4) M lignocaine. Lignocaine (10(-4) M) reduced the overflow of (3)H evoked by field stimulation at 5 Hz. It is suggested that the contractile responses to 5 Hz are due to nerve stimulation and that the increased overflow of (3)H is due to the stimulation of noradrenergic nerves.4 The overflow of (3)H evoked by field stimulation at 5 Hz was unaltered and increased by propranolol (10(-6) M) and phentolamine (10(-6) M), respectively. Clonidine (5 x 10(-5) M) had no effect in the absence but reduced the amount of (3)H which overflowed in response to field stimulation at 5 Hz in the presence of 10(-6) M atropine. The contractile responses to field stimulation at 5 Hz were reduced by phentolamine (10(-6) M) or clonidine (5 x 10(-6), 10(-5) and 5 x 10(-5) M) whether or not atropine (10(-6) M) was present. These results illustrate the presence of postsynaptic alpha-adrenoceptors and suggest the presence of presynaptic alpha-adrenoceptors in the gall bladder of the guinea-pig.