Tetsuo Hirano

Neural regulation of adrenal chromaffin cell function in the mouse — Stress effect on the distribution of [3H]dopamine in denervated adrenal medulla

Effects of adrenal denervation and stress on the distribution of radioactivity in the adrenal medulla after [3H]dopamine injection was studied by light microscopic autoradiography. Denervation of the adrenal gland abolished the stress (restraint plus water immersion) induced degranulation of adrenal chromaffin cells and decreased uptake of [3H]dopamine. Denervated chromaffin cell of stress mice incorporated as high radioactivity as those of no stress mice. Adrenal denervation increased the uptake in adrenaline-storing (A) cells but not in noradrenaline-storing (NA) cells. The characteristic distribution of radioactivity (high radioactivity along the cortico-medullary junction) was reinforced by adrenal denervation. Under stress conditions, increase in pituitary adrenocortical system did not enhance the uptake of [3H]dopamine in chromaffin cell while increase in nerve activity suppressed the uptake. Spontaneous activity of the splanchnic nerve to adrenal chromaffin cells suppresses the uptake of [3H]dopamine. The neural influence is stronger on A cells than on NA cells. Chromaffin cells in the subcortical zone are more intensely controlled by the neural influence than those in the central zone.

Projections of the postero-medial lateral suprasylvian area (PMLS) to cortical area 20 in cats with special reference to pupillary constriction: a physiological and anatomical study

Projections of the pupillo-constrictor area in the postero-medial lateral suprasylvian area (PMLS) to that in cortical area 20 was studied using electrophysiological and anatomical methods. Cats were injected with wheatgerm agglutinin-conjugated horseradish peroxidase in the latter area, which was located by intracortical stimulation. Retrogradely labeled cells were found in the PMLS pupillo-constrictor area. It was concluded that the pupillo-constrictor area in the PMLS has direct projections to that in area 20.

Characteristics and functions of two types of efferent fibers in the adrenal nerve

Two types of adrenal nerve fibers, AD and NA types, were identified by the presence or absence of inhibition of efferent activity after an intracarotid injection of isoproterenol (a beta-adrenergic stimulant). Efferent activity of both types was suppressed by adrenaline or noradrenaline injection. In AD-type fibers, suppression due to adrenaline or isoproterenol injection was blocked by a beta-adrenergic blocking agent (propranolol). In NA type fibers, the suppressive effect of adrenaline or noradrenaline was blocked by an alpha-adrenergic blocking agent (phenoxybenzamine). Dose-response characteristics showed that in AD-type fibers suppressive effect of adrenaline was always larger than that of noradrenaline, whilst in NA type fibers the two catecholamines caused the same degree of suppression of nerve activity. Two negative feedback loops for catecholamine secretion are suggested; one is between adrenaline level in the circulating blood and AD type nerve activity mediated be beta-adrenergic receptors, and the other is between noradrenaline level and NA type nerve activity, mediated by alpha-adrenergic receptors. Considering that AD-type fibers terminate on adrenaline-storing cells and NA type fibers terminate on noradrenaline-storing cells, it is suggested that beta-receptor--AD-type fibers--adrenaline-storing cell system controls adrenaline level and alpha-receptor--NA type fibers--noradrenaline-storing cell system controls noradrenaline level.

Neural regulation of adrenal chromaffin cell function in the mouse: fate and distribution of [3H] dopamine in denervated adrenal medulla

The distribution and time course of appearance and decline of radioactivity in denervated adrenal medulla of mice injected with [3H]dopamine was examined by autoradiography. Radioactivity irradiated from [3H]dopamine was increased from 7.5 min to 30 min, then decreased rapidly in both adrenaline-storing (A) cells and noradrenaline-storing (NA) cells of either intact or denervated adrenals. In subcortical A cells, the incorporation of radioactivity was increased by denervation while in NA cells and in A cells in the center of the medulla, the increment was not significant. In the denervated adrenals, the decline of [3H]dopamine-derived radioactivity was slower than that in the intact gland. The denervation increased the gradient in radioactivity from the surface to the center of the medulla. The present results suggest that the sensitivity to neuronal suppression of dopamine uptake in subcortical A cells is different from that in A and NA cells in the rest of the gland. The results also indicate a functional heterogeneity within a single type of chromaffin cells.

ACTH controls [3H]dopamine uptake in the adrenal chromaffin cell

Effect of hypophysectomy on the disposition of [(3)H]dopamine-derived radioactivity in the mouse adrenal medulla was examined by autoradiography. Chromaffin cells, both A and NA type, incorporated less radioactivity in the hypophysectomized mice (50 days after operation) than in normal control mice: this decrease in the [(3)H]dopamine uptake was restored by intraperitoneal injection of ACTH (for 26 days; starting from 24th day after hypophysectomy; 40 mug/gbw/day). In the control mice chromaffin cells near the cortico-medullary junction showed a higher radioactivity than those in the center: hypophysectomy obscured this specific distribution pattern which reappeared after ACTH treatment.

Uptake of [3H]2-deoxy-d-glucose and [3H]dopamine in adrenal chromaffin cells of the mouse

Deoxyglucose method was applied to adrenal chromaffin cells. It was shown that dichromate-fixation could fix [3H]deoxyglucose in tissue sections. Dichromate-fixation has two advantages as compared with glutaraldehyde-fixation: (1) two types of adrenal chromaffin cells, adrenaline-storing (A) cell and noradrenaline-storing (NA) cells, are distinguishable, (2) more [3H]deoxyglucose is retained in sections than in those fixed with glutaraldehyde. No difference was demonstrated in the uptake of deoxyglucose between A and NA cells while A cells incorporated more [3H]dopamine than NA cells. This indicates that such difference was not due to the different rate of glucose utilization.

Epinephrine suppression of efferent activity of the adrenal nerve

Efferent nerve activity was recorded from nerve filaments dissected from the adrenal nerves in the rabbit before and after deafferentation of baroreceptors. Suppression of efferent activity of the adrenal nerve was observed following an injection of DL-epinephrine into the carotid artery. This suppression of adrenal nerve activity preceded the hypertension induced by epinephrine. An injection of lidocaine into the carotid artery caused a temporary suspension of the inhibitory effect of epinephrine. Adrenergic blocking agents also inhibited the suppressive effect of epinephrine. An injection of arterial blood collected during electrical stimulation of the splanchnic nerve reduced adrenal nerve activity. The present results suggest that catecholamines released from the adrenal medulla reflexly inhibit adrenal nerve activity through epinephrine-sensitive structure in the brain.

Beta adrenergic stimulant suppression of efferent activity of the adrenal nerve

Efferent activity was recorded from nerve filaments dissected from the sympathetic nerve branches to the adrenal gland (adrenal nerve). An infusion of isoproterenol into the carotid artery suppressed the discharge of the adrenal nerve as did an equal dose of epinephrine whereas systemic blood pressure descended after isoproterenol injection. The beta blocking agent inhibited the suppression after epinephrine and isoproterenol application. The results suggest the existence of reflex inhibition of adrenal nerve activity through beta adrenergic receptors besides that of baroreceptors.

Circadian variation of [3H]dopamine handling in adrenal chromaffin cells of mice

Circadian variation of exogenous [3H]dopamine handling by adrenal chromaffin cells was examined using mice habituated to 08.00-20.00 h light cycle. Experiments were carried out at 00.00, 06.00, 12.00 and 18.00 h. [3H]Dopamine-derived radioactivity reached a peak at 2 min then decreased rapidly except at 18.00 h, when no particular peak was observed at 2 min but at 30 min in both intact and denervated adrenals. In intact adrenals, the 2-min peak at 06.00 h was suppressed by corticosterone while in denervated adrenals the 2-min peak remained. The present result indicates that quick turnover of [3H]dopamine was suppressed by a steroid surge at about 2 h before light to dark alteration. Normal innervation is necessary for corticosterone-induced suppression.

Uptake of [3H]dopamine in the mouse adrenal medulla during dark and light period

Uptake of exogenous [3H]dopamine in adrenal chromaffin cells of the mouse was studied by autoradiography under a 12-h light, 12-h dark cycle. The uptake of [3H]dopamine in adrenal chromaffin cells was markedly decreased in the dark period. The decrease was prevented by adrenal denervation. It is postulated that there is a neurally mediated suppression of [3H]dopamine uptake by adrenal chromaffin cells in the dark period. Adrenaline-storing (A) cells are more sensitive to the decreased sympathetic activity than noradrenaline-storing (NA) cells while increased sympathetic activity non-selectively affects both types of adrenal chromaffin cells.