The GABA(B) receptor allosteric modulator CGP7930, like baclofen, reduces operant self-administration of ethanol in alcohol-preferring rats.

GABA systems have been implicated as targets for ethanol at the cellular, molecular and behavioural level. The present study was designed to further examine the potential of the GABA(B) receptor as a target for regulating operant alcohol responding. Given that the prototypic agonist, baclofen, reduces the self-administration of alcohol, we hypothesized that the GABA(B) receptor allosteric modulator, CGP7930, might have similar actions but a reduced side-effect profile. In this context, inbred alcohol-preferring (iP) rats were trained to respond for 10% v/v ethanol in a fixed ratio paradigm; all drug testing was performed under an FR3 schedule. Both baclofen and CGP7930 independently reduced voluntary responding for 10% ethanol in a dose-related manner. Neither drug impacted upon responding for water. A combination of subthreshold doses of baclofen and CGP7930 was also able to reduce operant responding for ethanol, suggesting that CGP7930 is indeed acting to facilitate GABA(B) receptor-mediated signalling in this paradigm. These data demonstrate the potential of positive allosteric modulators of metabotropic GABA(B) receptors to regulate alcohol responding.

Establishment of primary cultures of rat olfactory bulb under serum-free conditions for studies of cellular injury.

Olfactory dysfunction has been implicated in various neurodegenerative diseases including Parkinson's and Alzheimer's disease but, despite intense interest in the neurobiology of the olfactory bulb (OB), studies of neurodegenerative mechanisms have not been attempted in primary OB cultures. This study was aimed at developing a primary OB culture under serum-free conditions in order to investigate injury and excitotoxicity in vitro. Olfactory bulbs from rat pups were rapidly trypsinised and mechanically dissociated and the resultant single cell suspension was centrifuged through a high bovine serum albumin concentration gradient to reduce cellular debris before being seeded in multi-well culture plates. Cells were plated in neurobasal medium containing 0.5 mM glutamine, 25 mM K(+), 2% B27 and 10% fetal calf serum (FCS) for 24 h and, after 1 day in vitro (div1), were maintained without FCS. At div8, neurones exhibited extensive neuritic networks, were present as a monolayer and were mainly bipolar and immunopositive for gamma-aminobutyric acid indicating that they were intrinsic OB neurones. At div8, neurones (positive for microtubule-associated protein-2, 73%) predominated over astrocytes (positive for glial fibrillary acidic protein, 27%). Cellular injury produced by staurosporine, hydrogen peroxide and kainate, when assessed by morphological and biochemical procedures, was shown to be concentration-dependent and significantly reduced the numbers of neurones and astrocytes. Further analyses of kainate-induced injury revealed the presence of TUNEL-positive cells (indicative of apoptosis) and increases in intracellular free calcium, both of which were antagonised by CNQX. Thus, the serum-free culture developed here is amenable to morphological and high throughput neurochemical analyses of mechanisms contributing to the injury of OB neurones in vitro.