Evidence for excitatory 5-HT2-receptors on XXXX brainstem neurones.

@entity2227 @entity5376 @entity3858 @entity10097 @entity3159 @entity750 @entity16645 @entity35 @entity20936 @entity6009 @entity1063 @entity20935
1. The technique of microiontophoresis was used to investigate the identity of the receptor mediating the excitatory effects of @entity750 ( @entity750 ) upon neurones in the midline of the medullary brainstem of the @entity35 in vivo. 2. The 5-HT1-like receptor agonists @entity20935 (5-CT) and @entity10097 ( @entity10097 ) failed to excite the majority of neurones excited by @entity750 . The mobilities of @entity20936 and @entity10097 when tested in vitro were found not to differ significantly from that of @entity750 , suggesting that the lack of effect of these agonists was not due to a lower rate of release from the microelectrodes. 3. The excitatory responses to @entity750 were attenuated by the @entity750 2-receptor antagonists @entity6009 and @entity3858 when applied microiontophoretically or administered intravenously (0.3 and 1 mg kg-1 respectively). Excitatory responses to @entity2227 and @entity1063 were not reduced. 4. The @entity5376 antagonist @entity16645 failed to attenuate selectively the excitatory response to @entity750 when applied either by microiontophoresis or administered intravenously (1 mg kg-1). 5. Microiontophoretic application of the alpha 1-adrenoceptor antagonist @entity3159 did not attenuate excitatory responses to either @entity750 or @entity1063 . Intravenously administered prazosin (0.8 mg kg-1) also failed to attenuate excitatory responses to @entity750 , but did block excitatory responses to @entity1063 . 6. These results suggest that 5-HT2-receptors, but not 5-HT1-like receptors, 5-HT3-receptors or alpha 1-adrenoceptors, are involved in the excitatory response of midline medullary neurones to @entity750 .
