Blood pressure, heart rate and motor activity in 6 inbred rat strains and wild rats (Rattus norvegicus): a comparative study.

Inbreeding for many generations under optimal environmental conditions may have favoured the survival of alleles for blood pressure increase in phenotypically normotensive rat strains. To prove this hypothesis we measured telemetrically systolic (SBP) and diastolic blood pressure (DBP), heart rate (HR) and motor activity (MA) in 6 inbred rat strains (BB, BN, LEW, DA, F344, WKY) and wild rats most probably possessing all of the alleles for normotension. For the first time it is shown that systolic blood pressure can significantly differ between normotensive inbred rat strains and that most probably some inbred rat strains will be characterised by a systolic blood pressure found in their progenitors, the wild rats. In addition, the typical night activity of rodents was not seen in 2 inbred rat strains. All findings together may be interpreted in the sense that most, if not all inbred rats strains have more or less disturbances in blood pressure, HR and/or MA and that there is most probably no "healthy" inbred rat strain available so that wild rats may be an alternative for crossing studies dissecting hypertension in particular and diseases in general.