Is gamma-aminobutyric acid ( GABA ) an autocrine excitatory transmitter in human pancreatic beta-cells?
Signaling via GABA and GABA(A)R constitutes an autocrine positive feedback loop in human beta-cells. The presence of GABA(A)R in non-beta-cells suggests that GABA may also be involved in the regulation of somatostatin and glucagon secretion.
These results provide no evidence that reducing 5-HT function alters the primary reinforcing effects of self-administered amphetamine. The increase in self-administration of a low dose of amphetamine observed in experiment 1 probably involves some other process such as increased resistance to extinction.