Decreased alpha1-adrenergic receptor binding in the cerebral cortex and brain stem during pancreatic regeneration in rats

Enhanced 5-HT(2A) receptor status in the hypothalamus and corpus striatum of ethanol-treated rats

AIM

Brain is the major target for the actions of ethanol and it can affect the brain in a variety of ways. In the present study we have investigated the changes in 5-HT level and the 5-HT(2A) receptors in the ethanol-treated rats.

METHODS

Wistar adult male rats of 180-200 g body weight were given free access to 15% (v/v) (approx.7.5 g/Kg body wt./day) ethanol for 15 days. Controls were given free access to water for 15 days. Brain 5-HT and its metabolites were assayed by high performance liquid chromatography (HPLC) integrated with an electrochemical detector (ECD) fitted with C-18-CLS-ODS reverse phase column. 5-HT(2A) receptor binding assay was done with different concentrations of [3H] MDL 100907.

RESULTS

The hypothalamic 5-HT content significantly increased (P < 0.001) with a decreased (P < 0.001) 5-HIAA/5-HT turnover in the ethanol-treated rats when compared to control. The corpus striatum 5-HT content significantly decreased (P < 0.01) with increased (P < 0.01) 5-HIAA/5- HT turnovers in the ethanol-treated rats when compared to control. Scatchard analysis of [(3)H] MDL 100907 against ketanserin in hypothalamus showed a significant increase (P < 0.001) in B(max )with a decreased affinity (P < 0.001) in ethanol-treated rats when compared to control. The competition curve for [3H] MDL 100907 against ketanserin fitted one-site model in all the groups with unity as Hill slope value. An increased K(i) and log (EC(50)) value were also observed in ethanol-treated rats when compared to control. Scatchard analysis of [3H] MDL 100907 against ketanserin in the corpus striatum of ethanol-treated rats showed a significant increase (P < 0.001) in B(max) and in affinity (P < 0.01) when compared to control. The change in affinity of the receptor protein in both corpus striatum and hypothalamus shows an altered receptor. The competition curve for [(3)H] MDL 100907 against ketanserin fitted one-site model in all the groups with unity as Hill slope value. There was no significant change in K(i) and log (EC (50)) value in ethanol-treated rats when compared to control.

CONCLUSION

The present study demonstrated the enhanced 5-HT(2A) receptor status in hypothalamus and corpus striatum. The ethanol-induced enhanced 5-HT(2A) receptors in the hypothalamus and corpus striatum has clinical significance in the better management of ethanol addiction. This will have therapeutic application.

Gamma-aminobutyric acid A receptor functional decrease in the hypothalamus during pancreatic regeneration in rats

OBJECTIVE

In the present study, we investigated the alteration of gamma-aminobutyric acid A (GABAA) receptors in the hypothalamus of rats during pancreatic regeneration.

METHODS

Three groups of rats were used for the study: sham operated, 72 hours partially pancreatectomized, and 7 days partially pancreatectomized. The GABA receptor assay was performed by using the [H]GABA as ligand to the Triton X-100-treated membranes, and displacement with unlabeled GABA and [H]bicuculline binding to the GABAA receptors was assayed in Triton X-100-treated synaptic membranes and displacement with unlabeled bicuculline.

RESULTS

The GABA content in the brain regions and pancreas of the sham and experimental rat groups was quantified by displacement method. In the hypothalamus, the high-affinity GABAA receptor binding showed a significant decrease in maximal binding (P < 0.01) and equilibrium dissociation constant (P < 0.05) in 72 hours and 7 days partially pancreatectomized rats. The content of GABA has significantly decreased in the hypothalamus during the regeneration of pancreas.

CONCLUSIONS

This effect of GABAA receptors in hypothalamus suggests a regulatory role during active regeneration of pancreas that will have significance in insulin secretion.

Decreased dopamine D(2) receptor function in cerebral cortex and brain stem: their role in hepatic ALDH regulation in ethanol treated rats

Ethanol exerts numerous pharmacological effects through its interaction with various neurotransmitters. The dopaminergic pathway is associated with cognitive, endocrine, and motor functions, and reinforcement of addictive substances or behaviours. Aldehyde dehydrogenase (ALDH) is a vital enzyme involved with alcohol metabolism and detoxification. In the present study, we investigated the role of cerebral cortex and brain stem dopamine D(2) receptors in the functional regulation on ALDH enzyme activity, in ethanol administrated rats. Two groups of rats were selected viz. control and alcoholic. Cerebral cortex, brain stem and the liver dopamine content was decreased significantly (P < 0.05, 0.05, 0.001, respectively) and homovanillic acid/dopamine (HVA/DA) ratio has significantly increased (P < 0.05, 0.001 and 0.001), respectively in ethanol treated rats when compared to control. Scatchard analysis of [(3)H]YM-09151-2 binding to synaptic membrane preparations of cerebral cortex and brain stem showed a significant decrease (P < 0.001, 0.05, respectively) in B (max) in ethanol treated rats compared to control and the K (d) also decreased significantly (P < 0.05). The ALDH analysis showed a significant increase (P < 0.05) in V (max) in cerebral cortex, plasma and liver of experimental rats when compared with control without having significant change in brain stem but with decreased K (m) (P < 0.001). Our results suggest that decreased function of dopamine mediated through DA D(2) receptor in the cerebral cortex and brain stem enhanced the brain, plasma and liver ALDH activity in ethanol treated rats. This ALDH regulation has significance to correct alcoholics from addiction due to allergic reaction observed in aldehyde accumulation.