Neurotransmitter and neuromodulator activity in the gustatory zone of the nucleus tractus solitarius

The rostral nucleus of the solitary tract (rNST) is the first central relay in the gustatory pathway. While previous investigations have provided a wealth of information on the pattern of central terminations of gustatory afferent fibers, the morphology of synaptic connections of rNST neurons and responses of second order neurons to taste stimuli applied to the tongue, little is known regarding the neurophysiological characteristics of synaptic transmission in rNST. We have used an in vitro brain slice preparation of the rNST to study the intrinsic biophysical properties, neuropharmacology and synaptic responses of rNST neurons. These experiments have revealed that rNST neurons respond to the excitatory amino acid neurotransmitter glutamate, as well as the inhibitory amino acid neurotransmitter gamma amino butyric acid (GABA). By use of glutamate receptor agonists and antagonists we have shown that rNST neurons have AMPA/kainate and NMDA ionotropic glutamate receptors, as well as matabotropic glutamate receptors. In addition, rNST neurons respond to both GABAA and GABAB receptor agonists. The nature of the transmission at the synapse between primary afferent fibers and second order neurons in rNST has been examined by electrical stimulation of the solitary tract to elicit post-synaptic potentials (PSP). Three types of monosynaptic PSP result from stimulation of the solitary tract: excitatory post-synaptic potentials, inhibitory post-synaptic potentials, and a complex mixture of excitatory and inhibitory potentials. These new discoveries provide details about synaptic transmission in rNST and thereby clarify the underlying mechanism by which gustatory information is processed.

[A study on P21(ras) in human lung cancer and body fluid of cancer patients]

The McAb of anti-P21(ras) has been used to screen 9 cases of human lung cancer tissues, 18 cases of samples and 2 cases of hydrothorax samples of lung cancer patients by means of PAGE-immunoblots. The expression of ras gene was found in 8 cases of human lung cancer among which the expression of 4 cases was higher than that of normal control. P21(ras) has not been detected in serum and hydrothorax samples of cancer patients. The present study indicated that there was P21(ras) in human lung cancer and normal control and the expression level of ras gene in lung cancer was related to the differentiation of cancer.