ABSTRACT
The effects of somatostatin and cysteamine injccted into the ventromedial nucleus of the hypothalamus (VMH) on somatostatin-like immunoreactivity (SLI) concentration in the gastric antral mucosa and portal vein plasma as well as the gastric acid secretion were studied in anesthetized rats. The SLI concentration in the gastric antral mucosa and portal vein plasma and the gastric acid output were significantly increased one hour after injection of somatostatin (o. 5 ?g/0.5 ?l) into the VMH. Four hours later, the SLI concentration in the mucosa was still higher than the control level, while the SLI level in the plasma and the acid secretion were close to those of controls. On the contrary, the SLI concentration in the mucosa and plasma and the acid output were markedly decreased at four hours after injection of cysteamine (15?g/0.5?l) into the VMH. The present results suggest that both exogenous and endogenous somatostatin in the VMH have a facilitory action on the gastric somatostatin concentration and its release as well as on the gastric acid secretion, thus providing evidence for hypothalamic control of gastric somatostatin and acid secretion.
ABSTRACT
Unit discharges of neurons of the hypothalamic ventromedial nucleus region (HVM) and its surrounding structures including paraventricular nucleus, anterior hypothalamic area,and hypolhalamic dorsomcdial nucleus, were recorded in the ureth-ane-anesthetized and flaxidel-immobilized rats. In HVM,8 of 82 units showed periodical fluctuations in discharge rate, which could be categorized into two types: (1) With alternating active and silent phases 5 (2) with gradually waxing and waning phases. The duration of cach cycle varied from 1 to 5 minutes in different neurons. The periodicity disappeared after intraperitoneal injection of nembutal, while the average discharge rate was raised somewhat. This result suggested that the depressing pha-s of periodical activity of the HVM neuron might probably result from the inhibitory action in certain neuronal circuit, rather than from the intrinsic property of the recorded neurons. The effect of picrotoxin was contradictory. No periodical activity was noted in the 47 recorded neurons outside of the HVM.
ABSTRACT
The types of synapses and some morphological features of the synaptic submicroscopic structures of rat hypothalamic ventromedial nucleus (HVM) have been described in this study. A total of 1 005 synapses is observed. The percentage of axo-dendritic synapse is 96.6%. It covers the majority of the total number of synapses. The percentage of axo-somatic synapse is 2.8% and axo-axonic synapse is 0.5% of the total number of the synapses. The crest synapse which is never reported in the HVM was found to be 0.1%. Its postsynaptic elements come from clubbed finger-like dendritic crest which is characterized by prominent postsynaptic membrane thickening and subsynaptic dense bodies. Two presynaptic terminals contact the wall of the crest process side by side and contain spheric vesicles. In the axo-dendritic and axo-somatic synapses, the parallel synapse (including synaptic complex), the tangent-like synapse and serial-like synapse have been observed.