Somatostatin (SRIF) receptors have been implicated in many disease states of the central nervous and endocrine systems as well as various cancers. Therefore, it is very important to investigate the signal transduction pathways of SRIF receptors in order to understand the molecular basis for the action of SRIF drugs. This paper identifies the G proteins coupled to rat brain SRIF receptors. The interactions of a neurotransmitter with G proteins previous to and following agonist binding are revealed. The results of these studies indicate that the signalling pathways regulated by a given neurotransmitter are strongly influenced by G proteins. Depending on the complement of G proteins expressed in a given cell, a transmitter may regulate multiple effector systems or a single effector system. G proteins, are, therefore, critical components in determining the physiological action of a given transmitter on a given tissue or cell population.
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