ABSTRACT
Background: In Nepali and Indian system of traditional medicine, Withania somnifera (WS) is considered as a rejuvenative medicine to maintain physical and mental health and has also been shown to improve memory consolidation. Objective: In this study, a methanolic extract of WS (mWS) was applied on mice hippocampal CA1 neurons to identify the receptors activated by the WS. Materials and Methods: The whole cell patch clamp recordings were performed on CA1 pyramidal neurons from immature mice (7‑20 postnatal days). The cells were voltage clamped at ‑ 60 mV. Extract of WS root were applied to identify the effect of mWS. Results: The application of mWS (400 ng/μl) induced remarkable inward currents (‑158.1 ± 28.08 pA, n = 26) on the CA1 pyramidal neurons. These inward currents were not only reproducible but also concentration dependent. mWS‑induced inward currents remained persistent in the presence of amino acid receptor blocking cocktail (AARBC) containing blockers for the ionotropic glutamate receptors, glycine receptors and voltage‑gated Na+ channel (Control: ‑ 200.3 ± 55.42 pA, AARBC: ‑ 151.5 ± 40.58 pA, P > 0.05) suggesting that most of the responses by mWS are postsynaptic events. Interestingly, these inward currents were almost completely blocked by broad GABAA receptor antagonist, bicuculline‑ 20 μM (BIC) (BIC: ‑1.46 ± 1.4 pA, P < 0.001), but only partially by synaptic GABAA receptor blocker gabazine (1 μM) (GBZ: ‑18.26 ± 4.70 pA, P < 0.01). Conclusion: These results suggest that WS acts on synaptic/extrasynaptic GABAA receptors and may play an important role in the process of memory and neuroprotection via activation of synaptic and extrasynaptic GABAA receptors.
ABSTRACT
BACKGROUND: The gonadotropin releasing hormone (GnRH) neurons represent the final output cells of the neural network that controls fertility. Dopamine (DA) has been shown to control gonadotropin release in many species. However, the direct membrane effects of DA and the related receptors on GnRH neurons remain poorly understood. The purpose of this study was to investigate the direct actions of DA on GnRH neurons and the related receptors using brain slice electrophysiology. METHODS: Gramicidin-perforated patch clamp recordings were made from the GnRH neurons to examine the direct membrane effects of DA in GnRH-EGFP mut5 mice. RESULTS: DA induced hyperpolarization of the GnRH neurons, which was maintained in the presence of tetrodotoxin (TTX), a Na+ channel blocker, suggesting a direct, rather than indirect, action of DA on GnRH neurons. DA-induced hyperpolarizing effects were blocked by prazosin, an alpah1-adrenergic antagonist, and mimicked by phenylephrine (PE), an alpha1-adrenergic agonist. CONCLUSIONS: These data indicate that DA exerts a direct inhibitory effect on GnRH neurons via the alpha1- adrenergic receptors. These results support the general concept that dopaminergic afference represents a predominantly inhibitory component of the GnRH neuronal network.