Behaviors induced by intrastriatal dopamine vary independently across the estrous cycle

Abstract

Unilateral intrastriatal injections of dopamine (DA; 25 micrograms/0.25 microliters) or amphetamine ( AMPHET ; 25 micrograms/0.25 microliters) induced contralateral postural deviation and contralateral rotation that varied systematically across the estrous cycle of Long-Evans hooded rats. Both the deviation and rotation elicited by either drug were suppressed during the early part of the day of proestrus (2-6 hours after lights on) and were enhanced on the day of estrus, compared to the other days of the estrous cycle. However, when the behaviors elicited by the two drugs were examined across the day of proestrus, it was found that postural deviation and rotation changed independently. Postural deviation elicited by intrastriatal DA and AMPHET was suppressed on the day of proestrus at 4 and 7 hours after lights on, but was enhanced to the level seen during estrus at 11 hours after lights on. In contrast, contralateral rotation induced by either drug was suppressed 4, 7 and 11 hours after lights on and was enhanced only by the morning of estrus. These data suggest that there are separate DA-modulated mechanisms within the striatum for postural deviation and contralateral rotation, and that these mechanisms are differentially affected across the estrous cycle.