Attenuation of chemically induced defence response by 5-HT1 receptor agonists administered into the periaqueductal gray |
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| Authors: | Simon R. G. Beckett Andrew J. Lawrence Charles A. Marsden Paul W. Marshall |
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| Affiliation: | (1) Department of Physiology and Pharmacology, Medical School, Queen's Medical Centre, NG7 2UH Nottingham, UK;(2) Pain Relief Foundation, Rice Lane, L9 1AE Liverpool, UK;(3) ICI Pharmaceuticals, Bioscience II, Mereside, Alderley Park, Macclesfield, Cheshire, UK |
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| Abstract: | The ability of 5-HT1 receptor agonists to modulate a chemically induced defence response has been studied in Lister hooded rats. Microinjections of the excitatory amino acidd,l-homocysteic acid (DLH) in both rostral and caudal dorsal periaqueductal gray matter (PAG) caused explosive motor behaviour characteristic of defence. This behaviour was quantified in terms of response duration, arena revolutions and number of defensive jumps. Direct administration into the PAG of either 5-carboxamidotryptamine (5-CT) or 8-hydroxy-2-(di-n-propylamino) tetralin (8-OHDPAT) produced behaviours (decreased exploratory rearing, dose related onset of flat body posture) indicative of 5-HT1A receptor activation. Pretreatment with either 5-CT or 8-OHDPAT directly in the PAG caused a significant attenuation, and in some cases a complete abolition, of the DLH evoked response. These agonists share high affinity in vitro for the 5-HT1A receptor. Thus the results suggest that in vivo activation of 5-HT1A receptors mediates an antiaversive reponse with respect to defensive behaviour elicited by specific chemical stimulation of the dorsal PAG. |
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| Keywords: | Excitatory amino acid Serotonin Aversion Periaqueductal gray 5-HT1A receptor |
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