GABA neurons

The mu, delta and kappa opioid receptors are coupled to G° and G proteins and the inhibitory actions of the opioids occur from the closing of calcium channels (in the case of the K receptor) and the opening of potassium channels (for /i, d and ORL-1). These actions result in either reductions in transmitter release or depression of neuronal excitability depending on the pre- or postsynaptic location of the receptors. Excitatory effects can also occur via indirect mechanisms such as disinhibition, which have been reported in the substantia gelatinosa and the hippocampus. Flere, the activation of opioid receptors on GABA neurons results in removal of GABA-mediated inhibition and so leads to facilitation. 

In addition to the loss of GAD staining (i.e. GABA) neurons and inhibitory symmetrical synapses around an alumina focus in primates (see above), studies with a chronically implanted cortical cup over a cobalt lesion (focus) in rats show an increased release of glutamate that is associated with spiking (Dodd and Bradford 1976). 

Lee, R. S., Steffensen, S. C. Henriksen, S. J. (2001). Discharge profiles of ventral tegmental area GABA neurons during movement, anesthesia, and the sleep-wake cycle. J. Neurosci. 21, 1757-66. 

Gao, X. B. van den Pol, A. N. (2001). Melanin concentrating hormone depresses synaptic activity of glutamate and GABA neurons from rat lateral hypothalamus./. Physiol. 533, 237-52. 

The reinforcing effects of opiate drugs involve a number of neuronal pathways [21]. In the VTA, opiates stimulate p-opioid receptors on GABA neurons that synapse on dopamine neurons. This inhibits the GABA neurons, leading to disinhibition of the dopamine neurons and enhanced dopamine release in the nucleus accumbens and other target areas (Fig. 56-3). Opiates also exert dopamine-independent effects in the nucleus accumbens by activating... 

Agnati, L.F., Ferre, S., Lluis, C., Franco, R. and Fuxe, K. (2003) Molecular mechanisms and therapeutical implications of intramembrane receptor/receptor interactions among heptahelical receptors with examples from the striatopallidal GABA neurons. Pharmacological Reviews, 55, 509-550. 

Peripheral neuropathies Amyotrophic lateral sclerosis Alzheimer s disease Parkinson s disease Huntington s disease Sensory/motor neurons Spinal motor neurons Forebrain cholinergic neurons Nigral dopamine neurons Striatal GABA neurons NGF, IGF-1, NT-3, CNTF BDNF, IGF-1, CNTF, GDNF, NT-4/5 NGF, BDNF, NT-4/5 GDNF, BDNF, NT-3, NT-4/5 BDNF, NT-4/5... 

Becquet, D., Faudon, M., and Hery, F. (1990) In vivo evidence for an inhibitory glutamatergic control of serotonin release in the cat caudate nucleus involvement of GABA neurons. Brain Res 519 82-88. 

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