Elsevier

Neuroscience

Volume 116, Issue 4, 28 February 2003, Pages 921-923
Neuroscience

Letter to neuroscience
Orexin A (hypocretin-1) application at the medial preoptic area potentiates male sexual behavior in rats

https://doi.org/10.1016/S0306-4522(02)00877-1Get rights and content

Abstract

The medial preoptic area plays an important role in the regulation of male sexual behavior in rats, and this area receives orexinergic inputs. The role of orexinergic inputs in the medial preoptic area in sexual behavior has not been studied, though they have been shown to play a role in some other physiological functions. In this study, the changes in male sexual behavior in rats were studied after local injection of orexin A (Hypocretin-1) at the medial preoptic area. The results of the study showed that orexin A application at the medial preoptic area increased sexual arousal as well as the copulatory performance. Sexual arousal is one of the physiological stimuli, which influences wakefulness. It is possible that the earlier reports showing increased wakefulness Espana et al 2001, Thakkar et al 2001, on application of orexin A at the medial preoptic area/basal forebrain, has a contribution from sexual arousal.

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Experimental procedures

The study was conducted on ten adult male Wistar rats, weighing 180–250 g. The animals were kept in controlled temperature (25±2 °C) under 14:10h light-dark schedule (light on at 6:00 A.M.). Food and water were provided ad libitum. The rats were screened for sexual behavior using standard criteria Mittimohan et al 1989, Mallick et al 1996 and those having a sex drive score above four were chosen for the study. Under sodium pentobarbital anesthesia (40 mg/kg body wt, i.p.), 26 gauge bilateral

Results and discussion

Seven rats in which OX-A was bilaterally injected at the mPOA were grouped together for statistical analysis. The bilateral microinjection of OX-A (0.3 nmol) in the mPOA (n=7) produced significant decrease in latencies to mount, intromission and ejaculation (Table 1). There was significant decrease in post-ejaculatory interval and mean inter-intromission interval (P<0.05) and increase in pursuit, mount, intromission frequencies (P<0.05) and sex drive scores (P<0.05). The OX-A treated rats were

Acknowledgements

Statistical help rendered by Dr. K. R. Sundaram, Department of Biostatistics, All India Institute of Medical Sciences, is acknowledged.

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